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      • Dependence of the modern icebreaker fleet from ice conditions on the Russian seas (Eng)

      Dependence of the modern icebreaker fleet from ice conditions on the Russian seas (Eng)

      6 August 2019 16:41
      // Transport
      I.O. Dumanskaya
      DOI: 10.24411/2658-4255-2019-10052

      html.png    PDF.png    XML.png  

      For Citing:  Dumanskaya I.O. Dependence of the modern icebreaker fleet from ice conditions on the Russian seas  / I.O. Dumanskaya // Russian Arctic. - 2019. - No. 5. - P.12. 

      Published: 06.08.2019 

      The paper considers the current status of Russian Icebreaker fleet. The potential application of sum of degree-days of frost to characterize easy, moderate and difficult ice conditions in the Russian seas is proved. The restrictions for different ice-class vessels to navigate in easy, moderate and difficult ice conditions are analyzed. It is shown that the power of the modern icebreaker fleet enables to navigate successfully in the Russian seas in conditions of mild and moderate winters, as well as in conditions of severe and extremely severe winters. The analysis of construction and operation of the modern icebreaker fleet in 21st century leads to the conclusion that the real challenge of winter navigation in the non-Arctic seas is not due to ice thickness but due to the increasing number and size of vessels requiring icebreaker assistance.

      Keywords: ice conditions, ice cover of the seas, ice thickness, power of the icebreaker, safety of the navigation, sum of the degree-days of frost

      Introduction
      Planning of maritime operations in the Russian seas during the ice period requires long-term forecasting into the forthcoming ice season. For this task Roshydromet engages Arctic and Antarctic Research Institute (AARI) to make background forecast for the Arctic seas for June-September, and Hydrometeorological Research Centre of Russian Federation (Hydrometcentre of Russia) to make background forecast for the non-Arctic seas for  the period from October till June of the forthcoming ice season. The AARI makes forecasts for the Arctic seas in March and June with earliness of 1 to 4 months. The Hydrometcentre makes forecast for the non-Arctic seas at the beginning of October with earliness of 2 to 8 months for different elements of ice regime (dates of beginning of ice formation and clearance of ice; maximum winter ice thickness; ice cover and duration of ice period in harbor areas). Accuracy of long-term forecast of the Hydrometcentre of Russia is 70-75% [2].

      Years of discussions regarding usefulness of long-term forecasts, and the lack of their acceptance by our foreign colleagues haven’t yet convinced Roshydromet to abandon the practice of making long-term forecasts. Long-term forecasts of AARI and Hydrometcentre of Russia are used in FGI (Federal Government Institution) ‘The Administration of the Northern Sea Route’ and FSUE (Federal State Unitary Enterprise) ‘Rosmorport’ for planning of icebreakers operation areas during the summer navigation in the Arctic and winter navigation in non-Arctic seas. The main practical task of long-term ice forecasting is to inform the maritime community about prospective severity of ice conditions in a certain sea. These conditions are supposed to be easy (E), moderate (M) or difficult (D).

      The term ‘difficult ice conditions’ is subjective and implies not only a certain geographic latitude and power of icebreaker fleet, but also the particular climate characteristics in which navigators are accustomed to operate. Shippping companies have changed significantly their definition of ‘difficult ice conditions’ over the past decade. On several occasions (e.g. in January, 2008 and in March, 2020) the experts of the Ministry of Transport of the Russian Federation (Mintrans of Russia ) consulted with Roshydromet on whether the ice conditions in the Sea of Azov were extremely difficult for navigation. In fact, in January, 2008 about 150 vessels awaited for icebreaker assistance near the ice edge, though by winter classification by sum of degree-days of frost (DDF), the winter of 2007/2008 (as well as the winter of 2011/2012) in the Sea of Azov was determined as moderate winter according to climatic stereotype of 20th century, while severe winter in the Sea of Azov is characterized by fast ice thicknesses of 45-60 cm [3].

      Similar problems have occurred in the Gulf of Finland where severe winter (according to stereotype of 20th century) hadn’t been observed for already 30 years (the last severe winter was in 1986/1987). During the navigation of 2010-2011 (‘moderate winter’) vessels were assisted by 10 icebreakers, however, due to the difficult ice situation, nuclear icebreaker ‘Vaygach’ had to be sent to the Gulf of Finland for the first time in the history. Icebreaker support was required to assist oil supertankers from Primorsk. Nuclear icebreakers assistance in the Gulf of Finland took place also in 2012 (nuclear icebreakers ‘Rossiya’ and ’50 Let Pobedy’) and in 2013 (nuclear icebreaker ‘Rossiya’).

      This paper aims to determine the relevance of  technical characteristics of icebreaker fleet in the different seas of Russia to sea ice conditions not only for the modern period of global warming but also for the most severe winters observed in 20th century.

      1. Data on hydrometeorological conditions and icebreaker fleet status

      Table 1 contains information about time-series of environmental characteristics used for analysis of easy, moderate and difficult ice conditions in different seas.

      Table 1 – Time series of environmental characteristics

      Sea

      Sea region or observation station

      Characteristics

      Observation period

      Observation period, years

      Kara Sea

      Dikson Island

      DDF

      1921-2018

      98

      FT

      1926-2018

      93

      White Sea

      Arkhangelsk

      DDF

      1813-2018

      206

      Mudyug Island

      FT

      1914-2018

      105

      Baltic Sea

      St.Petersburg

      DDF

      1811-2018

      208

      Kronstadt

      FT

      1911-2018

      108

      Vyborg

      FT

      1930-2018

      89

      Sea of Azov

      Rostov-on-Don

      DDF

      1882-2018

      137

      Taganrog

      FT

      1924-2018

      95

      Caspian Sea

      Astrakhan

      DDF

      1846-2018

      173

      Bol’shoy Peshnoy Island

      FT

      1930-2018

      89

      Iskustvenniy Island - Lagan

      FT

      1953-2018

      66

      Bering Sea

      Anadyr

      DDF

      1916-2018

      103

      FT

      1963-2018

      56

      Sea of Okhotsk

      Magadan

      DDF

      1933-2018

      86

      FT

      1933-1994

      65

      Poronaysk

      DDF

      1909-2018

      110

      Ayan

      FT

      1934-2018

      85

      Sea of Japan

      Aleksandrovsk-Sakhalinskiy

      DDF

      1891-2018

      128

      FT

      1953-2018

      66
































      Note: DDF – sum of degree-day of frost, FT - fast ice thickness

      The paper often refers to a vessel class, therefore Table 2 contains characteristics of ice classes of icebreakers and vessels. 
      Table 3 contains permissible marine operations and the corresponding ice conditions in the Arctic seas and the severe non-Arctic Bering Sea.
      Table 4 contains established restrictions for navigation in non-Arctic harbor areas.

      Table 2 – Characteristics of ice classes of icebreakers and vessels 

      Ice class

      Characteristics of icebreaking operations permitted

      Total power, kW

      Icebreaker,

      LL1

      In the Arctic seas (AS) on coastal routes and shore ice belt routes in high latitude all year round. Capable of forcing the way in compact ice field over 2.0 m thick.

       ≥47807   

      Icebreaker,

      LL2

      In the AS during the summer period and for operation on coastal routes during the winter period. Capable of forcing the way in compact ice field less than 2.0 m thick.

      22065 - 47807

      Icebreaker,

      LL3

      In shallow waters and mouths of rivers flowing into the Arctic seas during the winter period without assistance as well as for operation on coastal routes in the Arctic seas under convoy of icebreakers of higher category. Capable of forcing the way in compact ice field up to 1.5 m thick. 

      11032-22065

      Icebreaker,

      LL4

      In harbor and roadstead water areas without assistance all the year round as well as for operations in the non-Arctic freezing seas (NAS) under convoy of icebreakers of higher category during the winter period. Capable of forcing the way in compact ice field up to 1.0 m thick.

       < 11032   

      Vessel, Arc 9

      In AS in close ice up to 3.5 m thick during winter-spring navigation and up to 4.0 m thick during summer-autumn navigation

      -

      Vessel, Arc 8

      In AS in close ice up to 2.1 m thick during winter-spring navigation and up to 3.1 m thick during summer-autumn navigation; in navigable passage astern an icebreaker in ice up to 3.4 m thick during winter-spring and summer-autumn navigation.

      -

      Vessel, Arc 7

      In AS in close ice up to 1.4 m thick during winter-spring navigation and up to 1.7 m thick during summer-autumn navigation; in navigable passage astern an icebreaker in ice up to 2.0 m thick during winter-spring navigation and up to 3.2 m thick during summer-autumn navigation.

      -

      Vessel, Arc 6

      In AS in open ice up to 1.1 m thick during winter-spring navigation and up to 1.3 m thick during summer-autumn navigation; in navigable passage astern an icebreaker in ice up to 1.2 m thick during winter-spring navigation and up to 1.7 m thick during summer-autumn navigation.

      -

      Vessel, Arc 5

      In AS in open ice up to 0.8 m thick during winter-spring navigation and up to 1.0 m thick during summer-autumn navigation; in navigable passage astern an icebreaker in ice up to 0.9 m thick during winter-spring navigation and up to 1.2 m thick during summer-autumn navigation.

      -

      Vessel, Arc 4

      In AS in open ice up to 0.6 m thick during winter-spring navigation and up to 0.8 m thick during summer-autumn navigation; in navigable passage astern an icebreaker in ice up to 0.7 m thick during winter-spring navigation and up to 1.0 m thick during summer-autumn navigation.

      -

      Vessel, Ice 3

      Independent navigation open brush ice in NAS and in compact ice up to 0.7 m thick in navigable passage astern an icebreaker

      -

      Vessel,  Ice 2

      Independent navigation in open brush ice in NAS and in compact ice up to 0.55 m thick in navigable passage astern an icebreaker

      -

      Vessel, Ice 1

      Independent occasional navigation in open brush ice in NAS and in compact ice up to 0.4 m thick in navigable passage astern an icebreaker

      -

      Vessel, UL

      Independent navigation in AS during summer and autumn in easy ice conditions; all-year round  in NAS

      -

      Vessel, ULA

      Independent navigation everywhere in the World Ocean during summer and autumn

      -

       

      Table 3 - Restrictions for different ice classes to navigate in the Arctic seas and in the Bering Sea

      Type of ice conditions

      Description of ice conditions

      Ice class of vessels

      independent navigation

      navigation under icebreaker assistance

      Easy

      New, young and thin first-year ice (up to 0.7 m thick), appearance and presence of medium first-year ice (less than 1.2 m thick)  up to 25%

      Arc 4 or higher ice class

      Arc 4 or higher ice class

      Moderate

      Medium first-year ice (up to 1.2 m thick) in amount of 25% and more, which may include thick first-year ice (more than 1.2.m thick)  inclusions up to 25%

      Arc 7 or higher ice class

      Arc 6 or higher ice class

      Difficult

      Thick first-year ice (more than 1.2 m thick) and multi-year ice (more than 2 m thick) in amount of at least 25%  

      Arc 8-Arc-9

      Arc 7 or higher ice class

       

      Table 4 – Restrictions for different ice classes to navigate in non-Arctic seas

      Type of ice conditions

      Ice cover thickness

      Ice class of vessels

      Northern seas

      Southern seas

      independent navigation

      navigation under icebreaker assistance

      not allowed for navigation

      Easy

      Easy

      10-15 cm

      Ice 1 or higher ice class

      Vessels without ice strengthening

      Tugs and tows

      Moderate

      Moderate

      15-30 cm

      Ice 2 or higher ice class

      Ice 1

      Vessels without ice class, tugs and tows

      Moderate

      Difficult

      30-50 cm

      Ice 3 or higher ice class

      Ice 1 and Ice 2

      Vessels without ice class, tugs and tows

      Difficult

      Extremely difficult

      >50 cm

      Arc 4 or higher ice class

      Ice 2 and Ice 3

      Vessels without ice class or Ice 1, tugs and tows

      Note: Northern seas here are the White Sea, the Gulf of Finland, seas of Far-East; southern seas here are the Sea of Azov and the Caspian Sea.

       Table 4 shows:

      - Ice-strengthened vessels  Arc 4 and Arc 5 are allowed  to navigate  independently only in easy type of ice conditions;
      - Ice-strengthened vessels  Arc 6 are allowed  to navigate  independently in easy ice conditions and with icebreaker assistance in moderate ice conditions;
      - Ice-strengthened vessels  Arc 7 are allowed  to navigate  independently in moderate ice conditions and with icebreaker assistance in difficult ice conditions;
      - Ice-strengthened vessels Arc 8 and Arc 9 are allowed to navigate independently in all types of ice conditions.
      Comparison of Table 3 and Table 4 shows that similar ice conditions are considered as easy in the Arctic seas and in the Bering Sea, and extremely difficult in the Sea of Azov and the Caspian Sea.
      ‘Easy’ and ‘difficult’ ice conditions vary in the southern and the northern seas. Characteristics of ice-going vessels and the power of icebreaker fleet in different seas vary considerably. Historically association of icebreakers and vessels operating in specific sea is based on the moderate ice conditions in this sea. Table 5 represents real operating areas of icebreakers in the Russian seas approved by the Mintrans for the period of 2017-2018, and calculated average power of icebreakers (shaft power or propeller power for pod driven icebreakers).

      Table 5 – Operating areas of icebreakers and icebreaking vessels in 2017-2018, approved by the  Mintrans for icebreaker assistance in the freezing ports of Russia.

      Sea, region

      Operating area

      Icebreaker, tugboat

      Power, kW

      Average power, kW

      routes

      ports

      Kara Sea

      Kara Sea, Port of Sabetta

      NIB ’50 Let Pobedy’

      49000

      40750

      16000

      Kara Sea, Port of Sabetta

      NIB ‘Yamal’

      49000

      Gulf of Ob (Ob Bay), Port of Sabetta

      NIB ‘Vaygach’

      32500

      Yenisey Gulf

      NIB ‘Taymyr’

      32500

      Sabetta port area

      IB ‘Moskva’

      16000

      White Sea

      Sea, route

      IB ‘Dikson’

      7000

      16750

      3200

      Sea, route

      IB ‘Admiral Makarov’

      26500

      Ports of  Arkhangelsk, Severodvinsk, Onega

      IB ‘Kapitan Evdokimov’

      3800

      Ports of Arkhangelsk and Kandalaksha

      IB ‘Kapitan Kosolapov’

      2500

      Ports of Arkhangelsk and Onega

      IB ‘Kapitan Chadaev’

      3300

      Gulf of Finland

      The gulf, route

      IB ‘Kapitan Sorokin’

      16200

      18480

      3970

      The gulf, route

      IB ‘Ermak’

      26500

      The gulf, route

      IB ‘Murmansk’

      18000

      The gulf, route

      IB ‘Kapitan Nikolaev’

      16200

      The gulf, route

      IB ‘Novorossiysk’

      18000

      The gulf, route

      IB ‘Sankt Peterburg’

      16000

      Port of St. Petersburg

      IB ‘Mudyug’

      7000

      Port of St. Petersburg

      IB ‘Semen Dezhnev’

      3450

      Port of St. Petersburg

      IB ‘Ivan Kruzenshtern’

      3900

      Ust-Luga Sea Port

      IB ‘Karu’

      4160

      Ust-Luga Sea Port

      IB ‘Kapitan Plakhin’

      3300

      Ports of Vyborg and Vysotsk

      IB ‘Kapitan M.Izmaylov’

      2500

      Ports of Vyborg and Vysotsk

      IB ‘Yuriy Lisyanskiy’

      3500

      Sea of Azov

      Sea, route

      IB ‘Kapitan Moshkin’

      3800

      3600

      1180

      Sea, route

      IB ‘Kapitan Demidov’

      3800

      Sea, route

      IB ‘Kapitan Chudinov’

      3800

      Sea, route

      IB ‘Kapitan Zarubin’

      3300

      Sea, route

      IB ‘Kapitan Krutov’

      3300

      Port of Taganrog

      T/IB ‘Kama’

      1660

      Ports of Azov and Rostov-on-Don

      T/IB ‘Kapitan Kharchikov’

      1660

      Ports of Azov and Rostov-on-Don

      ‘Fanagoriya’

      544

      Port of Yeysk

      ‘Tekhflotets’

      1180

      Port of Yeysk

      ‘Kolguyev’

      860

      Caspian Sea

      Sea, Ports of Olya, Astrakhan

      IB ‘Kapitan Chechkin’

      3300

      3470

      3470

      Sea, Ports of Olya, Astrakhan

      IB ‘Kapitan Bukaev’

      3300

      Sea, Ports of Olya, Astrakhan

      IB ‘Kapitan Metsayk’

      3800

      Sea of Okhotsk

      Sea, route, Port of Magadan

      IB ‘Magadan’

      7000

      11600

      11600

      Sea, route, Prigorodnoye Sea Port

      IB ‘Kapitan Khlebnikov’

      16200

      Strait of Tartary

      Strait, route

      IB ‘Krasin’

      26500

      1610

      3320

      Strait, route, Port of Vanino

      MPSV ‘Spasatel Kavdejkin’

      5760

      Port of Vanino

      T ‘Khasanets’

      884

      Peter the Great Gulf

      Gulf, Port of Vladivostok

      T ‘Viktor Muhortov’

      883

      1490

      1490

      Gulf, Vostochny Port

      T ‘Olimp’

      1910

      Gulf, Port of Olga

      T ‘Barkhat 1’

      600

      Gulf, Port of Posyet

      T ‘Khasan’

      2029

      Gulf, Port of Posyet

      T ‘Aleut’

      2029

      Note: NIB – nuclear-powered icebreaker, IB – icebreaker, T – tugboat, MPSV - multipurpose salvage vessel

       2. Principles of classification of ice conditions into easy, moderate and difficult in the Arctic and non-Arctic seas


      According to the researches in the non-Arctic seas mild winters correspond to easy ice conditions, moderate winters correspond to moderate ice conditions, severe winters correspond to difficult ice conditions [1]. Classification of winters by sum of degree-days of frost is usual and has proved to be well in characterizing ice conditions in different seas. The eminent expert in ice navigation theory, particularly in icebreaking capability in the Arctic and non-Arctic seas, Gordiyenko P.A. used this approach as basic in his papers [9-11]. For his research on icebreaking capability, Gordiyenko looked at the movement through ice of various thickness of the diesel icebreaker ‘Moskva’  built in 1960 and possessing significant, for that period, propeller power of 16000 kW (with total power 19000 kW). Five new diesel icebreakers coming into commission in 2008-2016 (with the lead icebreaker of the series ‘Moskva’) have total power 21000-27840 kW.

      Recently the power of icebreakers has increased; furthermore, global climate is warming. Thus it is important not only to study whether it is enough to use sum of degree-days of frost to characterize different types of ice conditions, but also to determine whether the power of icebreaker fleet of a particular sea corresponds to observed ice conditions, and to understand what does ‘difficult ice conditions’ mean in this particular case.

      ‘Difficult’ ice conditions in the Gulf of Finland are only a relative term considering the modern state of the icebreaker fleet, for example, of the Northern-West basin Subsidiary of Rosmorport. The main reason of involving nuclear icebreaking fleet to the Gulf of Finland was not the severity of winters but necessity of providing broad waterways for supertankers.

      Nevertheless, the probability of actually severe winters like those described in unique observational materials on ice cover of 20th century, still exists. Data on ice conditions during the most severe winters of the entire period of observation, which corresponds to the most difficult ice conditions, is of great practical value.
      Designers of hydraulic structures and icebreakers base their calculations on extreme winter data. Thus, to estimate possible ice loads on the bridge pillars during the construction of the Kerch Strait Bridge, ice thickness in Taman, which was observed during the most extreme winter on the Sea of Azov in 1954 (64 cm), was used.

      Moreover, engineers enhance the power of nuclear icebreakers using information on extreme ice conditions in the Arctic region, which was observed in 1950-1990. Designed icebreaking capability of the most powerful up to date nuclear icebreakers ’50 Let Pobedy’ and ‘Yamal’ is 2.2-2.9 m (real value – 2.25 m). In 2012 AO ‘Baltic Shipyard’ started building a lead ship of the new class of icebreakers – project 22220 (LK-60Ya). The ships of the class have beam of 34 m, which is 4 meters wider than their predecessors, the ‘Arctica’ class icebreakers. It is essential for assisting large cargo ships. Moreover, the icebreaker of new class is able to combine function of deep-draft icebreaker for operating in the Central Arctic, and shallow-draft icebreaker working in the mouths of Siberian Rivers. This dual-draft icebreaker takes aboard 9000 tons of ballast water and changes its draft form 10.5 to 8.5 meters by the discharge of ballast water. The power of this class of ships is up to 60000 kW. The first ship of this class having legendary name ‘Arktika’ is expected to come into service in 2020, the next are expected to come into service nuclear-powered icebreakers ‘Sibir’ (in 2021) and ‘Ural’ (in 2022). At present, the construction of new project of nuclear icebreaker ‘Lider’ with power of 120000 kW, the beam of 47.7 m and designed icebreaking capability of 4.3 m is under discussion. This is the plan of Russian shipbuilders who enhance the guaranteed reliability of navigation in any ice conditions every decade. However, it would be good to observe balance between a desire to obtain funding for construction new super-icebreakers and real necessity of building such icebreakers.

      Long practice of hydrometeorological and ice services of navigation in the non-Arctic seas during the cold periods shows that downward bias of average sum of degree-days of frost of specific ice season may cause problems for ice navigation in any seas.

      The basis of dividing ice conditions in the Arctic seas into easy, moderate and difficult has been elaborated in AARI for many years. The expansion of industrialization of the North, longer navigation period, as well as an expected increase of cargo traffic in the Arctic by several times already to the 2024, require to specify types of ice conditions.

      The peculiarity of winter ice conditions in the Arctic is the presence of residual ice in the beginning of new ice formation. During the ice seasons of 1960-1980s this factor as well as the  cooling level (characterized by sum of degree-days of frost) affected the difficulty of ice conditions of the forthcoming and also the next-year ice seasons. The main underlying principle of the classification is unambiguous identification of ice conditions in the Arctic as easy, moderate or difficult.
      There is no identification of easy, moderate or difficult ice conditions in the normative documents of Rosmorrechflot (Federal Agency for Sea and Inland Water Transport of the Russian Federation) and Roshydromet. Few documents contain directives on permission for vessels to navigate the Northern Sea Route (NSR) in various ice conditions [8] and averaged information on permissible navigation areas and ice navigation conditions [7]. Valuable data for identification of easy, moderate or difficult ice conditions were accumulated during winter navigation of vessels by ‘Norilsk Nickel’ in the south-western part of the Kara Sea and in the Yenisei Gulf.

      Linear relations between DDF and some ice characteristics are studied to analyze the possibility of using the sum of degree-days of frost (DDF) as a single parameter to identify the type of ice conditions in different seas. Table 6 represents these relations.

      Table 6 –Correlation between sum of degree-days of frost (DDF) and ice characteristics in 7 non-Arctic seas

      Sea, sea region

      Relation between parameters:

      Linear function

      K

      Kara Sea

      DDF in Dickson and Hmax in the area of station Dickson

        0.0301*DDF+29.7

      0.72

      DDF in Dickson and Lmax in the Kara Sea

        0.0172*DDF-50.4

      0.55

      White Sea

      DDF in Arkhangelsk and Hmax in the area of station Mudyug

        0.0276*DDF+31.1

      0.70

      DDF in Arkhangelsk and Lmax in the Funnel of the White Sea

        0.0223*DDF+50.4

      0.61

      Baltic Sea

      DDF in St.Petersburg and Hmax in the area of station Kronstadt

        0.0321*DDF+29.9

      0.76

      DDF in St.Petersburg and Hmax in the area of station Viborg

        0.0296*DDF+33.2

      0.72

      DDF in St.Petersburg snd Lmax in the Gulf of Finland

        0.0696*DDF+36.2

      0.78

      DDF in St.Petersburg snd Lmax in the Baltic Sea

        0.0683*DDF+0.1

      0.87

      Sea of Azov

      DDF in Ristiv-on-Don and Hmax in the area of station Taganrog

        0.0589*DDF+11.7

      0.86

      DDF in Ristov-on Don and Lmax in the Sea of Azov

        0.1116*DDF+30.4

      0.76

      Caspian Sea

      DDF in Astrakhan and Hmax in the area of station Peshnoy

        0.0589*DDF+11.7

      0.86

      DDF in Astrakhan and Hmax in the area of station Iskustvenniy Island

        0.0449*DDF+7.5

        0.84  

      DDF in Astrakhan and Lmax in the North of the Caspian Sea

        0.0347*DDF+65.3

      0.77

      Bering Sea

      DDF in Anadyr and Hmax in the area of station Anadyr

        0.0356*DDF+3.2

      0.75

      DDF in Anadyr and Lmax in the Bering Sea

        0.0088*DDF+5.5

      0.62

      Sea of Okhotsk

      DDF in Magadan and Hmax in the area of station Ayan

        0.0473*DDF+4.2

      0.68

      DDF in Magadan and Lmax in the Sea of Okhotsk

        0.0298*DDF+6.6

      0.68

      DDF in Poronaysk and Lmax in the Sea of Okhotsk

        0.0428*DDF+3.5

      0.74

      Average DDF in Poronaysk and Magadan and Lmax in the Sea of Okhotsk

        00.0421*DDF-8.5

      0.77

      Sea of Japan, Strait of Tartary  

      DDF in Aleksandrovsk-Sakhalinskiy and Hmax in the area of station Aleksandrovsk-Sakhalinskiy 

        0.0473*DDF+4.2

      0.68

      DDF in Aleksandrovsk-Sakhalinskiy and Lmax in the Strait of Tartary

        0.0298*DDF+6.6    

      0.68

      Note: Hmax – maximum ice thickness for the ice season(cm); Lmax – maximum ice coverage during the ice season (%); K – correlation coefficient between calculated and observed characteristics.  

      Analysis of Table 6 represents strong correlation of sum of degree-days of frost with characteristics of ice conditions in the non-Arctic seas (for generalized period 1950-2018). Meanwhile, variability of correlation coefficient for different seas and characteristics varies from 0.6 to 0.8. The Kara Sea reveals weak correlation between DDF and average ice covering in September (K=0.55), indicating a necessity for additional parameters to describe the level of difficulty of ice conditions in the Arctic seas. AARI uses data on age characteristics of drift ice or on state of the arctic ice massif [12].

      Table 7 provides averaged quantitative information on permissible ice thickness at which vessel is able to navigate astern an icebreaker in open passage with low speed (2-5 knots) without increasing risk of damage due to interaction between ice and the hull. Table 8 provides information on permissible speed of vessel to navigate independently in different ice conditions.
       

      Table 7 – Ice class of vessel and corresponding permissible ice thickness for navigation with icebreaker assistance

      Ice class 

      Ice age,

       Ice thickness, m

      Winter-spring navigation

      Summer-autumn navigation

      Arc 4

      Thin first-year ice, up to 0.7 m

        Medium first-year ice, up to 0.9 m  

      Arc 5

      Medium first-year ice, up to 0.8 m

        Medium first-year ice, up to 1.2 m

      Arc 6

      Medium first-year ice, up to 1.2 m

        Thick first-year ice, up to 1.5 m

      Arc 7

      Thick first-year ice, up to 1.8 m

        Multi-year ice, up to 3.2 m

      Arc 8

      Multi-year ice, up to 3.2 m

        Multi-year ice, up to 3.4 m

      Arc 9

      Multi-year ice, up to 3.5 m

        Multi-year ice, more than 3.5 m

      Table 8 – Permissible speed (Vp) for independent navigation of different ice classes in various ice conditions

      Ice class

      Vp., knots

      Ice concentration, tenths

      Ice age

      Ice thickness, m

      Winter-spring navigation

      Summer-autumn navigation

      Arc 4

      6-8

      1-6/10

      First-year ice

      0.6

      0.8

      Arc 5

      «

      1-6/10

      First-year ice

      0.8

      1.0

      Arc 6

      «

      1-6/10

      First-year ice

      1.1

      1.3

      Arc 7

      «

      7-8/10

      First-year ice

      1.4

      1.7

      Arc 8

      10

      7-8/10

      Multi-year ice

      2.1

      3.0

      Arc 9

      12

      9-10/10

      Multi-year ice

      3.5

      4.0

      Data listed above shows that guiding limit of ice thickness for independent navigation of ice-strengthened vessels Arc 4-Arc 6 with permissible speed up to 6-8 knots (easy ice conditions) is 0.6-1.1 m with partial concentration of first-year ice up to 6 tenths. Various speed, ice thickness and partial concentration of ice of different age may give various combinations of speed-thickness-concentration, however, permissible ice thickness is the determining factor for vessels.

      Taking into account the principle of strict selection of criteria for classification, easy ice conditions for vessel classes Arc 4-Arc 6 and particularly Arc 7-Arc 9 are those with predominance of new ice, young ice and thin first-year ice (up to 0.7 m).

      Using the same approach, the limits of moderate ice conditions, which allow navigation with icebreaker assistance for ice-strengthened vessels Arc 6 and independent navigation for ice-strengthened vessels Arc 7, are ice thicknesses up to 1.2 and up to 1.4 m, respectively.

      Taking into account the principle of strict selection of criteria for classification, moderate ice conditions for ice-strengthened vessels Arc 6-Arc 7 and stronger classes (Arc 7-Arc 9) are those with predominance of first-year ice (ice thickness up to 1.2 m).

      Difficult ice conditions, which allow navigation without restrictions for vessel classes Arc 8-Arc 9 and with restrictions for vessel class Arc 7, are those with thick first-year ice and old ice (ice thickness more than 1.2 m).

      These limits coincide with ice age categories, which are identified on the Arctic sea-ice maps by international and national symbols of nomenclature of sea ice. Thus, determining the ice age is a standard procedure that doesn’t make any problem for captains and navigators of icebreakers and ice vessels.

      However, it should be considered that transformation of thin first-year ice to medium and subsequently to thick first-year ice can lasts from 10 to 40-50 days. The beginning of a thicker ice type formation doesn’t mean univocal change of type of ice conditions as it reduces subsequently the period of navigation. Establishing the fact of older ice age type must be determined reliably by satellite images and shipboard observations. The experience of icebreaker assistance and support of navigation shows that navigation should be continued till there is a possibility to avoid unfavorable ice by maneuvering.

      The experience of navigation and statistical calculations demonstrate that a vessel is able to avoid of unfavorable ice with partial concentration of 1-2 tenths by moving and maneuvering. It is substantially more difficult to avoid unfavorable ice with partial concentration more than 2-3 tenths, and it is totally impossible with 4-5 tenths.

      All mentioned above allows to extend the limits for chosen criteria of determination of the type of ice conditions. But it should be considered that the accuracy of interpretation of satellite images and determining of ice age and ice cover boundary is about ±1 tenths. Therefore it is suggested to establish 3 tenths (30% from total amount of all ice types) as a limit of permissible presence of unfavorable ice. This approach ensures the presence of unfavorable ice in case of mistake of interpretation (which occurred rarely) not more than 4 tenths (40%) from the total ice concentration, i.e. the level of concentration when it is impossible to avoid unfavorable ice.

      In the south-western part of the Kara Sea fast ice forms a narrow belt along the coastline in shallow waters and thus is not significance for navigation. Therefore it is suggested to exclude it from considering ice age categories.  

      In the north-eastern part of the sea fast ice formation all along the western passages to the Vilkitskiy Strait is possible. Fast ice there is an area of dynamic navigation and thus it is essential to consider its composition.

      Considering the above it is suggested to establish the following criteria (i.e. limiting values) to determine type of ice conditions in the Kara Sea for winter season.

      Easy ice conditions - new, young and thin first-year ice (up to 0.7 m) is observed, the presence of medium first-year ice up to 30% (Sav < 30%) is possible;

      Moderate ice conditions – medium first-year ice (up to 1.2 m thick) is observed in amount of 30% and more (Sm ≥ 30%), the presence of thick first-year ice up to 30% (Sth<30%) is possible;

      Difficult ice conditions – thick first-year ice (more than 1.2 m thick) and old ice are observed in amount not less than 30% (Sth ≥30%).

      During the winter-spring seasons first-year ice of autumn formation prevails in the Arctic sea routes in conditions of global warming of the 21th century, thus it is worthwhile to correlate ice types and sum of degree-days of frost the same way it was made above for the non-Arctic seas. Table 9 shows results calculated by function from Table 6 for ice thickness (H, cm) and sum of degree-days of frost (DDF) in the area of station Dikson (correlation coefficient K=0.72).

      Equation of converse relation is:

      DDF=33.2*H-987

       Table 9 – Ice class and corresponding permissible ice thickness for winter-spring navigation

        Ice class  

      Ice age,

      Ice thickness, cm

        DDF, ˚C  

      Arc4

      Thin first-year ice, up to 70 cm

      <1340

      Arc5

      Medium first-year ice, up to 80 cm

      <1670

      Arc6

      Medium first-year ice,  up to 120 cm

      <2300

      Arc7

      Thick first-year ice, up to 180 cm

      <4990

      Arc8

      Multi-year ice, more than 200 cm

      <5650

      Arc9

      Multi-year ice, more than 200 cm

      <5650

      Note: maximum observed DDF in the area of the Dickson Island was 5800˚C (in 1968/1969)

      The experience of previous research [1] shows that relation between DDF and ice characteristics of non-Arctic seas are the same in the area of 600-700 km from the representative observation station. This statement is true for station Arkhangelsk (White Sea) with meridional extent of about 500 km; for station Rostov-on Don (Sea of Azov) with meridional extent of about 180 km; for station Astrakhan (northern Caspian Sea) with meridional extent of about 270 km; for station Aleksandrovsk-Sakhalinskiy (Strait of Tartary) with meridional extent of about 650 km.

      Meridional extent of the Baltic Sea is 1200 km. The correlation coefficient between DDF in Saint-Petersburg and maximum ice cover in the Gulf of Finland is K=0.78. This relation is appropriate for the Gulf of Finland. However, the question is whether it is appropriate for the full area of the Baltic Sea. The area of interest is the northern part of the sea including the Gulf of Bothnia, which northern coastline is 700 km far from Saint-Petersburg.

      To verify the relation for the full area of the Baltic Sea, the relation between DDF in Saint-Petersburg and maximum ice cover of the Baltic Sea is calculated using the data of FIMR (Finnish Institute of Marine). The correlation coefficient in this case is even stronger (K=0.87) in comparison with the correlation coefficient for the Gulf of Finland. Evidently it is because in our study we artificially limit the area of ice cover in the Gulf of Finland in the west, which makes the correlation weaker.

      Meridional extent of the Bering Sea is about 1500 km, but ice covers usually the northern part of the sea. The longest ice route from Kresta Bay to the edge of ice cover is about 800 km. Sum of degree-days of frost is calculated using data of station Anadyr.

      It should be taken into account that warm water masses of the Pacific Ocean affect the location of the edge of ice cover in the far-Eastern seas (thus, affect the ice cover) and thereby reduce the impact of DDF on ice cover. Correlation coefficient between DDF in Anadyr and maximum ice cover in the Bering Sea is K=0.62 and is considered as sufficient. Correlation coefficient between DDF and ice thickness in Anadyr is significant (K=0.76).

      The Sea of Okhotsk covers an area of 1 583 000 km2, with meridional extent of 2200 km. Ice is observed in all regions of the sea. It is the most difficult sea to determine the ice conditions. The large extent of the sea causes the differences in temperature and ice regime in the northern, central and southern parts of the sea. Thus, extremely severe winter in the northern part of the Sea of Okhotsk was observed in 1965-1966, with abnormally low temperatures extended to the south to the latitude of the Shantar Islands; at the same time moderate winter was observed in the southern part of the sea. Typical situation during the severe winters in the central and southern parts of the Sea of Okhotsk is almost total covering by ice. Such situation was observed in 2001, with severe winter in the area from Bolshoy Shantar Island to Yuzhno-Kurilsk and, at the same time, moderate winter in the north of the Sea of Okhotsk (according to the data of Okhotsk and Magadan stations). In this case it is reasonable to divide the sea into two parts: northern part (northward of 54º N), and central-southern part (southward of 54º N). Calculations for the northern part of the Sea of Okhotsk are based on the data of station Magadan, calculations for the central-southern part are based on the data of station Poronaysk.

      Table 10 provides information on the criteria of various ice conditions in the non-Arctic seas.

      Table 10 – Criteria of different ice conditions in the non-Arctic seas

      Sea, sea region

      Station

      Criteria based on DDF, °C

      Easy ice conditions (mild winter)

      Moderate ice conditions (moderate winter)

      Difficult ice conditions (severe winter)

      White Sea

      Arkhangelsk

      <1140

      1140-1710

      >1710

      Baltic Sea, Gulf of Finland

      St.Petersburg

      <480

      480-940

      >940

      Sea of Azov

      Rostov-on-Don

      <215

      215-585

      >585

      Caspian Sea

      Astrakhan

      <265

      265-640

      >640

      Bering Sea, Gulf of Anadyr

      Anadyr

      <3310

      3310-3940

      >3940

      Sea of Okhotsk, northern part

      Magadan

      <2150

      2150-2575

      >2575

      Sea of Okhotsk, mid-southern part

      Poronaysk

      <1530

      1530-1960

      >1960

      Sea of Japan, Gulf of Tartary

      Aleksandrovsk-Sakhalinskiy

      <1635

      1635-2015

      >2015

       

      3. Relation between sum of degree-days of frost and the power of icebreakers fleet in the Russian seas

      It is possible to use the sum of degree-days of frost not only for specification of ice conditions. Linear relationship between DDF and the technical characteristics of icebreaker is useful for planning maritime operations.

      Positive practical experience of using icebreakers to support winter navigation in the non-Arctic Russian seas and year-round navigation in the Arctic seas, as well, enables Mintrans of Russia to set the operating areas for icebreakers. The most powerful icebreakers operate in the Arctic, while low-powerful icebreaking vessels operate in non-Arctic southern seas.

      Table 11 represents the correspondence of average icebreaker power in a certain sea to average DDF, average thickness of fast ice (Hf) and floating ice (Hfl) in the period of maximum ice development.

      To evaluate ice conditions correctly it is important to learn the correlation between the thicknesses of fast and float ice. Karelin [4] analyzed data on ice thickness measurements during the drift of icebreaker ‘Lenin’ in 1937-1938 in the Arctic and compared them with fast ice thickness; thus in his research he concluded that ice thickness of smooth floating ice was 5-25% less than thickness of fast ice. Mironov in his researches [5, 6] shows that the difference between floating and fast ice thicknesses was 25-30% according to the observational data in the Laptev Sea in April-May 1988. In Table 11 the thickness of floating ice is calculated as 20% less than the thickness of fast ice.

      Data from Table 11 (columns 4 and 6) enables to plot the relation between DDF and floating ice thicknesses in the Russian seas (Figure 1) with strong correlation (K=0.97).

      Table 11 – Average power of icebreakers (Sav) and corresponding average ice characteristics

      Sea, sea region

        Sav, kW  

      Station (DDF/Hf)

        DDF, °C  

        Hf, cm  

        Hfl, cm  

      1

      2

      3

      4

      5

      6

      Kara Sea

      40750

      Dikson/Dikson

      4400

      158

      126

      White Sea

      16750

      Arkhangelsk/Mudyug Isl.

      1480

      70

      56

      Baltic Sea, Gulf of Finland

      18480

      St.Petersburg/Krondstast

      770

      51

      41

      Sea of Azov

      3600

      Rostov-on-Don/Taganrog

      400

      37

      30

      Northern Caspian Sea

      3470

      Astrakhan/Iskustvenniy Isl.

      460

      28

      22

      Sea of Okhotsk, northern part

      11600

      Magadan/Ayan

      2300

      118

      94

      Sea of Japan, Gulf of Tartary

      1610

      Aleksandrovsk-Sakhalinskiy/ Sovetskaya Gavan

      1790

      100

      80

      Sea of Japan, Peter the Great Gulf

      1490

      Vladivostok/Vladivistok

      1120

      55

      50

       

      Figure 1 – Relationship between the thickness of floating ice and the sum of degree-days of frost.

      Equation of this linear relationship is:
      Hfl=0.026·DDF +21 (1),
                   Hfl – average thickness of floating ice, cm
                  DDF – sum of degree-days of frost, °C.

      Equation of converse relation:
      DDF=36.023· Hfl-657 (2)

      Data of Table 11 is also used to plot the relationship between average power of icebreakers and:
      - thickness of floating ice corresponding with average ice conditions in various seas (Fig. 2a);
      - average actual sum of degree-days of frost (Fig. 2b).

      Icebreaker power which is required for different ice thicknesses, thus, is calculated using the relation:
      Sav=254.5· Hfl-3655.7 (3),
                  Sav – average power of icebreaker, kW,
                  Hfl – average thickness of floating ice, cm.

      Icebreaker power (Sav) for a particular sum of degree-days of frost is calculated using the relation:
      Sav=8.071· DDF-614.2 (4).

      Figure 2b shows the possibility of using air temperature data for evaluation of the required average power of the icebreaker fleet.



        Figure 2 – Relationship between average power of icebreaker and (a) floating ice thickness or (b) sum of degree-days of frost.

      Table 12 provides data on designed icebreaking capability during the maritime operations in the Russian seas. Sum of degree-days of frost (column 7 of Table 12) corresponding with designed ice thickness is calculated by equation (2).

      Table 12 – Designed icebreaking capability and corresponding sum of degree-days of frost

      N

      Icebreaker

        Ice class  

        Delivered power, kW  

        Shaft power, kW  

        Vo, knots  

        Hmax, m  

        DDF, °C  

      1

      2

      3

      4

      5

      6

      7

      8

      1.                 

      ’50 Let Pobedy’

      NIB, LL1

      49000

      55200

      22

      2.2-2.9

      7268

      2.                 

      ‘Yamal’

      NIB, LL1

      49000

      55200

      22

      2.2-2.9

      7268

      3.                 

      ‘Taymyr’

      NIB, LL2

      32500

      36800

      18.5

      1.7-2.0

      5467

      4.                 

      ‘Vaygach’

      NIB, LL2

      32500

      36800

      18.5

      1.7-2.0

      5467

      5.                 

      ‘Krasin’

      IB, LL2

      26500

      30420

      19.8

      1.6-1.7

      5107

      6.                 

      ‘Admiral Makarov’

      IB, LL2

      26500

      30420

      19.8

      1.6-1.7

      5107

      7.                 

      ‘Ermak’

      IB, LL2

      26500

      30438

      19.5

      1.6-1.7

      5107

      8.                 

      ‘Murmansk’

      IB, LL3

      18000*

      27840

      17

      1.0-1.5

      2945

      9.                 

      ‘Vladivostok’

      IB, LL3

      18000*

      27840

      17

      1.0-1.5

      2945

      10.             

      ‘Novorossiysk’

      IB, LL3

      18000*

      27840

      17

      1.0-1.5

      2945

      11.             

      ‘Kapitan Dranitsyn’

      IB, LL3

      16200

      18240

      13

      1.0-1.5

      2945

      12.             

      ‘Kapitan Nikolaev’

      IB, LL3

      16200

      18240

      19

      1.0-1.5

      2945

      13.             

      ‘Kapitan Sorokin’

      IB, LL3

      16200

      18270

      19

      1.0-1.5

      2945

      14.             

      ‘Kapitan Khlebnikov’

      IB, LL3

      16200

      18264

      19

      1.0-1.5

      2945

      15.             

      ‘Sankt Peterburg’

      IB, LL3

      16000*

      21000

      17

      1.0-1.5

      2945

      16.             

      ‘Moskva’

      IB, LL3

      16000*

      21000

      17

      1.0-1.5

      2945

      17.             

      ‘Tor’

      IB, LL4

      8200

      10172

      15

      0.8-1.0

      2224

      18.             

      ‘Dikson’

      IB, LL4

      7000

      9560

      16.5

      0.8-1.0

      2224

      19.             

      ‘Mudyug’

      IB, LL4

      7000

      9560

      16.5

      0.8-1.0

      2224

      20.             

      ‘Magadan’

      IB, LL4

      7000

      9560

      16.5

      0.8-1.0

      2224

      21.             

      ‘Karu’

      IB, LL4

      4160

      5550

      13

      0.8-1.0

      2224

      22.             

      ‘Kapitan Evdokimov’

      River IB

      3800

      4815

      14

      0.7-0.9

      1865

      23.             

      ‘Kapitan Metsayk’

      River IB

      3800

      4815

      14

      0.7-0.9

      1865

      24.             

      ‘Kapitan Moshkin’

      River IB

      3800

      4815

      14

      0.7-0.9

      1865

      25.             

      ‘Kapitan Demidov’

      River IB

      3800

      4815

      14

      0.7-0.9

      1865

      26.             

      ‘Kapitan Chudinov’

      River IB

      3800

      4815

      14

      0.7-0.9

      1865

      27.             

      ‘Kapitan Chadaev’

      River IB

      3300

      4650

      14

      0.7-0.9

      1865

      28.             

      ‘Kapitan Chechkin’

      River IB

      3300

      4650

      14

      0.7-0.9

      1865

      29.             

      ‘Kapitan Bukaev’

      River IB

      3300

      4650

      14

      0.7-0.9

      1865

      30.             

      ‘Kapitan Krutov’

      River IB

      3300

      4638

      14

      0.7-0.9

      1865

      31.             

      ‘Kapitan Zarubin’

      River IB

      3300

      4650

      14

      0.7-0.9

      1865

      32.             

      ‘Kapitan Plakhin’

      River IB

      3300

      4650

      14

      0.7-0.9

      1865

      33.             

      ‘Ivan Kruzenshtern’

      IB, LL4

      3900

      4500

      14

      0.7-0.9

      1865

      34.             

      ‘Semen Dezhnev’

      IB, LL4

      3450

      4500

      14

      0.7-0.9

      1865

      35.             

      ‘Yuriy Lisyanskiy’

      IB, LL4

      3500

      3975

      14

      0.7-0.0

      1865

      36.             

      ‘Kapitan M.Izmaylov’

      IB, LL4

      2500

      3912

      13

      0.6-0.7

      1504

      37.             

      ‘Kapitan Kosolapov’

      IB, LL4

      2500

      4400

      13

      0.6-0.7

      1504

      38.             

      ‘Sevmorput’

      LASH, UL

      29420

      20.8

      0.8-1.0

      2945

      39.             

      ‘Spasatel Kavdejkin’

      MPVS, Arc5

      5760

      15

      0.8-1.0

      2224

      40.             

      ‘Khasan’

      T, Arc4

      2029

      12

      0.6-0.7

      1504

      41.             

      ‘Aleut’

      T, Arc4

      2019

      12

      0.6-0.7

      1504

      42.             

      ‘Olimp’

      T, Ice3

      1910

      11.5

      0.5

      1144

      Note: Vo - open water speed, LASH - nuclear-powered icebreaking LASH (lighter aboard ship) carrier, MPSV - multipurpose salvage vessel, T – tugboat. For the icebreakers with pod drives (matched with *) the term ‘shaft power’ is incorrect, the correct one is ‘propeller power’.

       

      Data provided by the Table 12 are used to plot the relationship between the designed power of icebreakers and:
      - ice thickness corresponding with lower limit of designed icebreaking capability (it is evident that upper limit of icebreaking capability is rare achievable);
      - sum of degree-days of frost corresponding with lower limit of designed icebreaking capability.

      The equations of linear regressions relate the icebreaker power to designed ice thickness and DDF. The designed power of icebreaker is correlated with ice thickness by equation:

      Sd=284.31·Hd-14482 (5),
                 Sd – designed power of icebreaker, kW;
                 Hd – designed ice thickness, cm.

      Designed power of icebreaker is correlated with sum of degree-days of frost by equation:
      Sd=7.8926·DDF-9296 (6).


      Figure 3 – Relationship between the designed power of icebreaker and the thickness of floating ice (a) or the sum of degree-days of frost (b) associated with lower limit of designed icebreaking capability.

      Figure 4a represents the combined plots of correlation between:
      a) ice thickness and average power of actual icebreakers operated in different seas;
      b) ice thickness corresponding with lower limit of designed icebreaking capability, and designed power of icebreaker.

      Figure 4b represents the combined plots of correlation between:
      a) sum of degree-days of frost and average power of actual icebreakers operated in different seas;
      b) sum of degree-days of frost, corresponding with lower limit of designed icebreaking capability, and designed power of icebreaker.

       

      Figure 4 – Relationships between power of icebreaker and a) designed (black line) and average actual (red line) ice thickness; b) designed (black line) and average actual (red line) sum of degree-days of frost.

      Analysis of relationships in the Figure 4a reveals that average power of icebreakers, which provide the satisfying assistance of vessels in the Russian seas, exceed the optimal (designed) power for equal ice thicknesses. This is due to fact that actual icebreakers often operate in areas of hummocked ice, which require more power input to break it. Besides,  ice conditions can be more difficult than moderate.

      Figure 4b is of special interest. Analysis of relationships reveals that sum of degree-days of frost during winters with moderate ice conditions is significantly less (by about 1000oC) than sum of degree-days of frost corresponding with power of icebreakers usually operated in the Russian seas. Icebreaker fleet, thus, has considerable power reserve in case of more difficult than moderate ice conditions. To evaluate whether this reserve power is sufficient to operate in conditions of extremely severe winter, the deviations of extreme values of DDF from mean values are calculated (Table 13). According to the data, the reserve is sufficient.

      Table 13 – Deviations of extreme values of sum of degree-days of frost (DDFmax) from mean values (DDFmean)

      Sea, sea region 

      Observation station  

        DDFma  x

        DDFmean  

        Δ DDF  

      White Sea

      Archangelsk

      2325

      1480

      845

      Gulf of Finland

      St. Petersburg

      1800

      770

      1030

      Sea of Azov

      Rostov-on-Don

      1277

      400

      877

      Northern Caspian Sea

      Astrakhan

      1240

      460

      780

      Sea of Okhotsk, northern part

      Magadan

      2955

      2300

      655

      Sea of Okhotsk, Central-southern part   

      Poronaysk

      2276

      1720

      556

      Mean

      790

      Conclusions

      The research has indicated the following:
      1. Sum of degree-days of frost is sufficient to characterize ice conditions in the non-Arctic seas and can be used alone to determine the type of ice conditions. To chara
      cterize ice conditions in the Arctic seas additional parameters should be used.
      2. Sum of degree-days of frost can be also used for calculation of powers of icebreakers in particular ice conditions to set operating areas.
      3. The power of the modern icebreaking fleet enables to navigate successfully in the Russian seas equally in conditions of mild and moderate winters, and in conditions of severe and extremely severe winters.
      4. Icebreaker fleet has considerable power reserve which is sufficient to cover all possible deviations of temperature regime which can turn moderate ice conditions into difficult.
      5. Long-term ice forecasts of the forthcoming ice navigation season predict mild and moderate winters corresponding with easy and moderate ice conditions due to global warming.
      6. The power of icebreakers built in 21th century exceeds significantly the power of icebreaker fleet in the latter half of the 20th century. Meanwhile, two opposite processes are observed: increasing power of built and designed icebreakers from the one hand, and decreasing ice thickness in all Russian seas due to sustainable warming from the other. Thus, the approach of classification of ice conditions into easy, moderate and difficult, which is based on temperature variability (DDF), doesn’t represent real challenges of ice navigation.
      7. Actually challenging conditions for ice navigation are revealed to occur in following situations:
      - Lack of icebreakers for assistance due to increasing ship traffic on the route;
      - The beam of an icebreaker is insufficient to assist super-ships (for ex., super tanker with beam of 50m);
      - The main icebreaker in the region is underpowered for moderate ice conditions in the sea (for ex., IB “Magadan” in the Sea of Okhotsk);
      - Icebreaking capability is decreased due to exhausted lifetime;
      - Convoy of vessels meets with hummocked and ridged ice zone; there is presence of vessels with ice class which is not in compliance with moderate ice conditions in the sea;
      -  A technical accident.
      8. The concept of easy, moderate and difficult ice conditions corresponding with winter severity is still used by navigators in excuse of problems during their winter navigation, though ice conditions are usually not the main challenge.  Obviously, during the loss of way in ice as a result of any reason, the presence of ice complicates a situation and turns almost any ice conditions to difficult.

      References:

      1. Dumanskaya I. O. Ice conditions of the seas of the European part of Russia. Moscow: IG–SOCIN, 2014, 605 p.
      2. Dumanskaya I. O. Method of long-term forecast of ice conditions in the Tatar Strait, the sea of Okhotsk and the Bering sea, based on the use of statistical modeling// Informational collection of the Hydrometeorological center of Russia. 2018.  No. 45, p. 117-126.
      3. Dumanskaya I. O., Kotilevskaya A. M., Fedorenko A.V. Ice conditions of the seas of the European part of Russia in the conditions of climatic changes (lessons of winter 2007-2008)// Meteorological. 2008.  No. 2, p. 134–144.
      4. Karelin, D. B. Influence of salinity of water and currents on the ice growth// Problems of the Arctic. 1943. No. 1, p. 144-149.
      5. Mironov E. U. Some regularities of ice thickness distribution in the Arctic basin//Proceedings of the Russian Geographical Society.1986. Vol. 118. Issue 3, p. 202-207. 
      6. Mironov E. U., Kuznetsov I. M. Some features of spatial unevenness of the thickness of stationary and drifting ice. Sat. Research of ice conditions of the Arctic seas, methods of calculation and forecast// Proc. AARI. 1990. Vol. 423, p. 42-53. 
      7. Rules of classification and construction of ships. Volume 1. Saint-Petersburg: Publishing house of the Russian Maritime register of shipping, 2015. 580 p.
      8. Rules of navigation in the waters of the Northern sea route. Moscow: Publishing house of the Ministry of transport of Russia, 2013. 18 p. 
      9. Accounting for ice conditions in hydrometeorological support of winter swimming in the Sea of Azov. Edited by P. A. Gordienko.  Leningrad: Hydrometeoizdat, 1979. 106 p. 
      10. Accounting for ice conditions in hydrometeorological support of winter swimming in the Baltic Sea. Edited by P. A. Gordienko.  Leningrad: Hydrometeoizdat, 1979. 167 p.
      11. Accounting of ice phenomena in hydrometeorological support of winter swimming in the Caspian Sea. Edited by P. A. Gordienko.  Leningrad: Hydrometeoizdat, 1983. 131 p.
      12. Yulin A. V., Charitonov M. V., Pavlova E. A., Ivanov V. V. Seasonal and interannualchanges of ice massifs in East Siberian sea// Arctic and Antarctic Research. 2018.  No. 3. p. 229-240.

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