Научная статья на тему 'On the History of the Arctic Ocean Exploration and the Arctic Sea Ice Cover'

On the History of the Arctic Ocean Exploration and the Arctic Sea Ice Cover Текст научной статьи по специальности «Науки о Земле и смежные экологические науки»

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Ключевые слова
modern marine polar research / icebreakers / expedition / international cooperation / современные морские полярные исследования / ледоколы / экспедиции / международное сотрудничество

Аннотация научной статьи по наукам о Земле и смежным экологическим наукам, автор научной работы — Jörn Thiede

Deciphering the Arctic Ocean paleoenvironments and their interaction with the Eurasian hinterland during the Cenozoic represents one of the most exciting chapters of the paleoclimatic history of planet Earth. The impact of the alternating glacial and interglacial climatic intervals during Late Cenozoic on the Arctic Ocean is one of the most important problems of modern polar research which opened up during the past decades due to the employment of modern capable research vessels which made the central Arctic Ocean accessible. Even though modest insights were possible based on short sediment cores taken from ice island stations earlier, major progress was only achieved when modern heavy duty research icebreakers capable to reach the central Arctic deep-sea basins could be deployed. They allowed to acquire long cores whose sediment composition reflected the impact of the alternating glacial and interglacial intervals during the youngest geological past, as originally defined by Köppen, Wegener and Milankovitch. The ice breakers involved were Ymer and Oden (both Sweden), Kapitan Dranitsyn, Akademik Federov and Akademik Tryoshnikov (Russia), Healy (US), Polarstern (Germany) and Amundsen (Canada). More recently they were joined occasionally by research icereakers from China, Japan and Korea. It became quickly clear that the fresh water influx from the Eurasian continental hinterland had a major impact on the formation and stability of the Arctic Ocean sea ice cover. Close linkages have been established to the history of the Siberian river drainage system as well as to the waxing and waning of the Pleistocene Eurasian ice sheets. Iodp and Ecord brought the first scientific drilling vessels into the Arctic Ocean and demonstrated that Cenozoic northern hemisphere glaciations started already during Eocene times, thus well before the Quaternary

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Из истории изучения Северного Ледовитого океана и ледового покрова арктических морей

Расшифровка палеосред Северного Ледовитого океана и их взаимодействие с евразийскими внутренними районами в кайнозое представляет собой одну из самых захватывающих глав палеоклиматической истории планеты Земля. Влияние чередующихся ледниковых и межледниковых климатических интервалов позднего кайнозойского периода на Северный Ледовитый океан является одной из важнейших проблем современных полярных исследований, которая стала изучаться в последние десятилетия благодаря использованию современных сверхмощных научно-исследовательских судов, сделавших доступным центральный район океана. Первые выводы были сделаны на основе изучения небольших кернов, взятых во время работы дрейфующих станций, но значительный прогресс был достигнут только тогда, когда появилась возможность осуществлять исследования на современных мощных ледоколах и исследовательских судах ледового класса, способных достичь глубоководных районов Центральной Арктики. В ходе рейсов таких судов были взяты длинные керны, состав отложений которых отражал влияние чередующихся ледниковых и межледниковых интервалов в течение самого молодого геологического периода, как первоначально определяли Кёппен, Вегенер и Миланкович. Среди судов, принимавших участие в таких экспедициях, были ледоколы «Имер» и «Оден» (Швеция), «Капитан Драницын» (Россия), «Хэви» (США), «Полярштерн» (Германия) и «Амундсен» (Канада), а также НЭС «Академик Фёдоров» и «Академик Трёшников» (Россия). В последние годы к ним время от времени присоединялись исследовательские ледоколы из Китая, Японии и Кореи. Удалось установить, что приток пресной воды из континентальных глубин Евразии оказывает существенное влияние на формирование и устойчивость ледового покрова Северного Ледовитого океана. Были выявлены тесные связи с историей сибирской речной системы, а также с наступанием и отступанием плейстоценовых евразийских ледяных щитов. Комплексная программа морского бурения (IODP) и Европейский консорциум по исследованию океана и бурению (ECORD) вывели первые научные буровые суда в Северный Ледовитый океан, и было установлено, что кайнозойские оледенения северного полушария начались уже во времена эоцена, то есть задолго до четвертичного периода

Текст научной работы на тему «On the History of the Arctic Ocean Exploration and the Arctic Sea Ice Cover»

J. THIEDE

On the History of the Arctic Ocean Exploration and the Arctic Sea Ice Cover

ТИДЕ Й.

Из истории изучения Северного Ледовитого океана и ледового покрова арктических морей

Author:

Jörn Thiede, professor, Doctor of Sciences, Köppen-Laboratory, Institute of Earth Sciences, St. Petersburg State University (St. Petersburg, Russia) jthiede@geomar. de

Сведения об авторе:

Тиде Йорн, профессор, доктор наук, Кёппен-Лаборатория Института наук о земле СПбГУ (Санкт-Петербург, Россия) jthiede@geomar. de

Abstract

Deciphering the Arctic Ocean paleoenvironments and their interaction with the Eurasian hinterland during the Cenozoic represents one of the most exciting chapters of the paleoclimatic history of planet Earth. The impact of the alternating glacial and interglacial climatic intervals during Late Cenozoic on the Arctic Ocean is one of the most important problems of modern polar research which opened up during the past decades due to the employment of modern capable research vessels which made the central Arctic Ocean accessible. Even though modest insights were possible based on short sediment cores taken from ice island stations earlier, major progress was only achieved when modern heavy duty research icebreakers capable to reach the central Arctic deep-sea basins could be deployed. They allowed to acquire long cores whose sediment composition reflected the impact of the alternating glacial and interglacial intervals during the youngest geological past, as originally defined by Köppen, Wegener and Milankovitch. The ice breakers involved were Ymer and Oden (both Sweden), Kapitan Dranitsyn, Akademik Federov and Akademik Tryoshnikov (Russia), Healy (US), Polarstern (Germany) and Amundsen (Canada). More recently they were joined occasionally by research icereakers from China, Japan and Korea. It became quickly clear that the fresh water influx from the Eurasian continental hinterland had a major impact on the formation and stability of the Arctic Ocean sea ice cover. Close linkages have been established to the history of

the Siberian river drainage system as well as to the waxing and waning of the Pleistocene Eurasian ice sheets. lodp and Ecord brought the first scientific drilling vessels into the Arctic Ocean and demonstrated that Cenozoic northern hemisphere glaciations started already during Eocene times, thus well before the Quaternary.

Аннотация

Расшифровка палеосред Северного Ледовитого океана и их взаимодействие с евразийскими внутренними районами в кайнозое представляет собой одну из самых захватывающих глав палеоклиматической истории планеты Земля. Влияние чередующихся ледниковых и межледниковых климатических интервалов позднего кайнозойского периода на Северный Ледовитый океан является одной из важнейших проблем современных полярных исследований, которая стала изучаться в последние десятилетия благодаря использованию современных сверхмощных научно-исследовательских судов, сделавших доступным центральный район океана. Первые выводы были сделаны на основе изучения небольших кернов, взятых во время работы дрейфующих станций, но значительный прогресс был достигнут только тогда, когда появилась возможность осуществлять исследования на современных мощных ледоколах и исследовательских судах ледового класса, способных достичь глубоководных районов Центральной Арктики. В ходе рейсов таких судов были взяты длинные керны, состав отложений которых отражал влияние чередующихся ледниковых и межледниковых интервалов в течение самого молодого геологического периода, как первоначально определяли Кёппен, Вегенер и Миланкович. Среди судов, принимавших участие в таких экспедициях, были ледоколы «Имер» и «Оден» (Швеция), «Капитан Драницын» (Россия), «Хэви» (США), «Полярштерн» (Германия) и «Амундсен» (Канада), а также НЭС «Академик Фёдоров» и «Академик Трёшников» (Россия). В последние годы к ним время от времени присоединялись исследовательские ледоколы из Китая, Японии и Кореи. Удалось установить, что приток пресной воды из континентальных глубин Евразии оказывает существенное влияние на формирование и устойчивость ледового покрова Северного Ледовитого океана. Были выявлены тесные связи с историей сибирской речной системы, а также с наступанием и отступанием плейстоценовых евразийских ледяных щитов. Комплексная программа морского бурения (IODP) и Европейский консорциум по исследованию океана и бурению (ECORD) вывели первые научные буровые суда в Северный Ледовитый океан, и было установлено, что кайнозойские оледенения северного полушария начались уже во времена эоцена, то есть задолго до четвертичного периода.

Keywords:

modern marine polar research, icebreakers, expedition, international cooperation. Ключевые слова:

современные морские полярные исследования, ледоколы, экспедиции, международное сотрудничество.

Introduction

The first generation of dedicated polar research vessels

The prize to have planned the first dedicated polar research vessel goes to Fridtjof Nansen who was going to use the brand-new Fram for his Arctic transpolar drift expedition 1893-1896 (Nansen, 1897). He succeeded to prove that the Arctic Ocean comprised a deep-sea basin, to collect the first, though very short sediment samples and measurements of atmospheric and hydrographic properties. The Fram was a modern research platform at her time and provided safe living conditions for the crew while being frozen into the ice and drifting passively across the Arctic Ocean. Fram's construction principles were used a bit later also for building the Maud (another Norwegian dedicated polar research vessel) and the Gauss which has been used for Germany's first true Antarctic expedition in 1901-1903 (Drygalski, 1904), but she was also the last one of this first generation of dedicated polar and oceanographic research vessels.

Although ice breaker technology was further developed in the ensuing decades (as can be shown exemplary by the Russian Krassin), no emphasis was paid to their deployment with research goals until the late 70ies of the last century. Research in the central Arctic was conducted mainly from ice islands (such as the Russian North Pole stations from 1937 onwards; Frolov et al., 2005) or the US-American T-3 station which did not provide for enough power to handle heavy instrumentation, but still allowed for a wide range of geophysical, biological, glaciological and hydrographic measurements. It was to take another close to 80 years for the next generation of dedicated polar research vessel to be deployed; in this paper I shall attempt to sketch this development, in an eclectic and somewhat subjective way leaning on my own experiences.

A new age of Arctic Ocean and polar research

The Swedish YMER-80 expedition

The Swedish VEGA under the command of A. E. Nordenskjold returned to Stockholm on April 24, 1880 after successfully traversing the Northeast passage. This was to be celebrated by Sweden and a commemorative expedition on a heavy duty ice breaker Ymer (Fig. 1) usually engaged in keeping sea lanes open for shipping during the cold seasons in the northern Baltic Sea. The plan was to repeat the traverse of the Northeast passage to the North of Eurasia and then to return through the Northwest passage back to Sweden during the Ymer-80 expedition (Schytt, 1981). The Ymer was manned by Swedish navy personell which resulted in that the Sovjet Union at that time categorically declined the application of Sweden to cross the Eurasian shelf seas. Even though disappointing at first, it forced a change in the Swedish plans and

Fig. 1. The Swedish icebreaker Ymer, platform of the YMER-80 expedition in 1980. Source: Göteborgs universitetsbibliothek

Fig. 2. Course track of the Swedish YMER-80 expedition (from Schytt, 1983)

the expedition was rerouted to the Barents Sea and its northern continental margin, to a crossing of Fram Strait and to Northeastern Greenland (Fig. 2). Scientifically this was a major challenge because it required a redefinition of the scientific program of the expedition and the installation of lab facilities as well as heavy instrumentation which would allow to probe unknown deep-sea areas; it would also force the Ymer to enter the Arctic Ocean in regions which were permanently sea ice covered and whose ice properties had not been properly investigated in relation to the ice breaking capabilities of the Ymer. It was indeed a courageous undertaking, and the results of the YMER-80 expedition opened up a completely new chapter of Arctic Ocean research. The Ymer was not yet a truly dedicated research ice breaker, but its expedition really opened a new chapter of Arctic Ocean research. It paved the way for the research ice breakers which are now active in exploring the deep central Arctic Ocean.

The scientific program of the YMER-80 expedition covered (Schytt, 1983) investigations of 1) the chemistry of the Arctic atmosphere with a special focus on pollution from distant industrial activities, 2) marine biology, and 3) marine geology/geophysics, with emphasis on bottom sediments along the expedition route with the aim to establish the extent of former glaciations and past climatic variations. The geoscientific activities of the expedition were particularly successful, as it managed to collect valuable geophysical data (Bostrom & Thiede, 1981) and the first very long sediment cores from the ice covered deep-sea basins to the North of Svalbard (Bostrom & Thiede, 1984).

The second generation of dedicated polar research vessels

YMER-80 expedition opened up a completely new chapter of marine polar research and for the employment of dedicated polar research vessels. Suddenly relatively large groups of scientists covering a multitude of disciplines were able to visit unknown regions of the ice-covered high latitude deep-sea basins for extended periods. Their ships provided for sophisticated laboratories and for enough power to handle heavy instruments during extended expeditions. Many of these new ships, however, had a dual purpose, namely the supply of polar research stations on land, both in the Arctic, as well as in the Antarctic, with the result that much research time was lost to their role in logistics.

It is not the purpose of this paper to provide for a complete catalogue of all members of this generation of polar research vessels, and because of personal familiarity I will concentrate on a few typical examples. They include the Swedish Oden and the Russian Kapitan Dranitsyn, which are heavy duty ice icebreaker not really built for science, but which at special occasions with great care were finished with specialized equipment to carry out scientific work. On the other side were the German Polarstern, the USCG Cutter Healy and the

Fig. 3. The German research ice breaker Polarstern on the river Weser in front of the Alfred-Wegener-Institute (AWI) in Bremerhaven, together with the yacht Grönland which originally has been used during the 1st German North Pole expedition in 1868. (Source: AdP - Archive of German Polar Research at the AWI)

2 Russian vessels Akademik Federov and Akademik Tryoshnikov, which had been built beside their logistic tasks to function as advanced polar research vessels with sophisticated laboratories, enough space and comfortable living conditions to provide platforms for long expeditions of international and interdisciplinary research groups.

Entering the deep-sea basins of the central Arctic Ocean

The German Polarstern (Fig. 3) represents the main scientific infrastructure of the German polar institute, now called the Alfred-'Wegener-Institute, Helmholtz-Center for Marine and Polar Research in Bremerhaven / Germany. She made her maiden voyage in 1982 and was conceived as research and supply vessel to service the permanent German Antarctic station (now called Neumayer III) and to provide a research platform for all marine disciplines, active both in the Southern and in the Arctic oceans.

Research icebreakers with conventional propulsion systems at the North Pole

The increasing international collaboration in Arctic marine research and the recognition of the improved abilities of the new generation of polar research

Fig. 4. Long box core from the central Arctic Ocean, recording a sequence of sediment layers from the Late Quaternary Glacials (grey layers) and Interglacials (brownish layers) in the corelab of Polarstern. Such cores could only be taken from research ice breakers providing tools to handle such instruments (Source: AdP-AWI)

Fig. 5. Polarstern in heavy seas crossing the Southern Ocean during one of her logistic trips to Antarctica (Source: AdP-AWI)

Fig. 6. The Swedish Oden, German Polarstern and USCG Cutter Healy (shadow in the mist to the left of both ships) in the ice of central Eastern Arctic Ocean (Source: AdP-AWI)

vessels soon led to attempts to systematically investigate the deep-sea basins of the central Arctic Ocean (Fig. 6). Two examples shall be given:

In 1991 a large effort was organized between 3 ice breakers (the Swedish Oden, the German Polarstern and the USCG Polar Star (International Arctic Ocean Expedition 1991). While the latter ship experienced some technical problems after entering the ice, Oden (cf. Anderson & Carlsson, 1991) and Polarstern (cf. Futterer et al., 1992) operated in tandem and succeeded to reach the Lomonosov Ridge and finally on Sept. 7, to reach the North Pole. The joint efforts of both ships allowed to collect highly valuable underway seismic reflection data across the crest of Lomonosov Ridge which later provided the basis to define the locations of the drill sites of the ECORD ACEX Expedition in 2004 (see further below). Reaching the North Pole offered an opportunity to the scientific parties of both ships with members from Australia, Canada, Finland, Germany, Norway, Sweden and USA to celebrate the success of the international effort (Figs. 6 and 7). Beside geophysical and marine geological work from Polarstern the research program was devoted to the study of ocean waters, air and ice, mainly conducted from Oden (Anderson & Carlsson, 1991).

Fig. 7. On September 7, 1991 German Polarstern and Swedish Oden reached the North Pole. It was the first time that a large international and interdisciplinary marine polar expedition and 2 research ice breakers with conventional propulsion systems succeeded to enter the at that time permanently ice covered central Arctic Ocean (Source: AdP- AWI)

The second example of successful international cooperation to be mentioned in this section was an expedition conducted jointly by the USCG Cutter Healy (Michael and Shipboard Scientific Party, 2001) and Polarstern (Thiede and Shipboard Scientific Party, 2002): AMORE - Arctic Mid-Ocean Ridge Expedition. Its aim was to establish detailed bathymetric maps of the crest area of Gakkel Ridge, to sample its volcanic rocks and to identify hydrothermal vent areas. The ships operated for some time in tandem to allow for geophysical profiling and it soon showed that Healy was the more capable icebreaker which several times had to break Polarstern out of the ice, Then the ships would part again for their individual mapping and sampling programs.

In summary, AMORE became a great success (see cited cruise reports by Michael et al., 2001 and Thiede et al., 2002 for details). The ships established bathymetric maps of the northern and southern shoulders of Gakkel Ridge with its anomalous deep rift valley and they dredged basement rocks at numerous locations (basalts, gabbros, peridotites) and observed volcanic highs reaching up to a few hundred meters of water depth. Long sediment was taken for stratigraphic and paleoceanographic work. Geochemical and temperature anomalies allowed to identify several regions of hydrothermal activity.

Fig. 8. USCG Cutter Healy on her way into the central Arctic Ocean (Source: J. Thiede)

Research Icebreaker activities during the decades 1990-2010

The map of the distribution of the stations occupied by Polarstern in the Arctic during the first 25 years of her activities reflects in many ways an important historic development. Similar maps for other research icebreakers for this region could certainly be drafted and depending on their nationality would probably look a bit different, but reflect similar trends.

This map displays the results of an exciting chapter of Arctic Ocean exploration, namely the heavy emphasis on detailed studies of the Fram-Strait area, the first deep penetration of the central Arctic in 1987 when the Gakkel Ridge was reached (Thiede, 1988, Pfirman & Thiede, 1992) the first visit of the North Pole in 1991 and opening of the Russian territorial waters and EEZ to foreign research vessels (from Thiede & Futterer, 2008).

The density of Polarstern stations in the Norwegian-Greenland Sea and particular the Fram Strait demonstrate the early cautious approach to the deployment of this young ship during the early years of activity. Polarstern (cf. Figs 3, 5 and 6) had been taken into service as the German polar research and supply ship to serve both its Antarctic interest and needs to supply the permanently manned Neumayer Station on the Ekstrom Iceshelf in the Weddell Sea. From 1983 onwards she spent many northern hemisphere summer seasons on research devoted to research in the Nordic Seas and the Arctic Ocean, mostly in international collaborative projects together with colleagues from the Scandinavian countries, later also from Russia. In 1987 the first transect into the deep Eastern Arctic Ocean was attempted resulting in a rich collection of glaciological, hydrological data and long sediment cores urgently needed to revolve the late Quaternary history of the Arctic sea ice cover (Polyak et al., 2010). The region between the Svalbard and Gakkel Ridge a region which had been visited previously only by Fridtjof Nansen's expedition 1893-1896 (Nansen, 1897) and by the Russian North Polar

Fig. 9. Cruise (expedition) tracks of German Polarstern in the Norwegian-Greenland Sea and Arctic Ocean during her first 25 years

drifting stations since 1937 (Frolov et al., 2006). Then, 1991 the first two research icebreakers (the Swedish Oden and the German Polarstern) with conventional propulsion systems reached the North Pole (Fig. 7) and demonstrated that the favorable ice conditions which had developed during the 90ies and later, permitted such ships to operate in most regions of the central Arctic Ocean and thus opening for a new age of the least known basin of the of the world ocean.

Exploration of the Eurasian Shelf Seas

Political changes in Russia during the early nineties resulted in another major historic development. Previously Russian Eurasian shelf seas were virtually closed to non-Russian research vessels. If any, new data could only be collected in close cooperation with Russian institutions and from Russian vessels. The map of Polarstern stations (Fig. 9) demonstrates the successful international cooperation between Russian and foreign research institutions. It involved not only the German Polarstern, but also the Swedish Oden, naturally also a host of Russian ships, such as Akademik Petrov of the RAS Vernadsky Institute, then Kapitan Dranitsyn (Fig. 10) from Murmansk and the small geotechnical drill ship Kimberlit. It is impossible to systematically mention all the cooperative projects and an exemplary selection has to be made.

Eurasian shelf seas play a crucial role for the properties and history of the Arctic sea ice cover because the Siberian rivers deliver large amounts of

Fig. 10. Then Russian Kapitan Dranitsyn is a conventional heavy duty icebreaker of the Murmansk Shipping Company. It was employed as research platform during the Russian-German expedition to study the freeze-up of the Laptev Sea in October 1995 (Kassens et al., Thiede, 1997) (Source: Dr. Rasmus CAU Kiel)

fresh water reducing the salinity of the shelf sea surface waters. Hence large amounts of new sea ice are formed in the Kara, Laptev and East Siberian seas. Outstanding results of such investigations were collected during expeditions from Russian RV Akademik Boris Petrov of the RAS Vernadsky Institute and from the Murmansk ice breaker Kapitan Dranitsyn.

The Akademik Boris Petrov was engaged in the Russian-German SIRRO-project investigating the impact of the drainage of the Ob and Yenisei rivers into the Kara Sea (Stein et al., 2003). The cruise reports cover five expeditions between 1997 to 2002 and explain the sampling strategies at stations reaching from the estuaries of both rivers out into the open Kara Sea. The voluminous book by Stein et al., 2003 summarize the collected data and cover A) Modern discharge - Data and Modelling; B) Discharge and biological processes; C) Discharge and organic carbon cycle, and D) Discharge and sediment records. It is a highly valuable addition to the numerous publications by Russian institutions in Murmansk, Moscow and St. Petersburg.

The Laptev Sea to the East of the Kara Sea with the extensive delta of the Lena River and its interaction with the continental hinterland has been the subject of 30 years of international investigations, with the aim to understand the dynamics of sea ice formation during all seasons of the year, under

Fig. 11. The Russian Akademik Tryoshnikov of the AARI during transit in the port of Kiel (Germany) (Source: Dr. Kassens, GEOMAR)

the frame of the Russian-German joint Laptev Sea System and Transdrift expeditions (Kassens et al., 1997; Rachold et al., 1997).

International partnerships in central Arctic Ocean exploration

The exploration of the central Arctic Ocean has been the subject of national research programs which have been increasingly internationalized. Typical examples of national programs are the efforts of the five Arctic Ocean rim states which have tried to define their EEZ (Exclusive Economic Zone) and which requires a precise definition of the geological properties of the continental margins and their seafloors.

Particular comprehensive efforts to achieve this have been launched by Russia (Laverov et al., 2013; Nikishin et al., 2021), but also by Denmark and Canada in their attempts to extend their EEZ over large tracts of the Arctic Ocean seafloor including the North Pole region.

The international cooperation in Arctic Ocean exploration, driven by the pressing climate problem has offered many new opportunities. Figs. 11 and 12 show the two modern research icebreakers of the AARI in St. Petersburg which played a crucial role when Polarstern conducted the MOSAiC-expedtion. The Akademik Tryoshnikov was visiting the port of Kiel (Germany) to load scientific cargo and instruments to be used during a joint Russian-German expedition to the Laptev and East Siberian seas. She is also occasionally visiting this port in transit from or to Antarctica when resupplying Russian stations. In Fig. 12 Polarstern and Akademik Fedorov are shown in the central Arctic Ocean during the 2019/2020 MOSAiC-expedtion. Despite the global Corona-pandemic the AWI had

Fig. 12. The German Polarstern and the Russian Akademik Fedorov of the AARI during the MOSAiC expedition2019/2020 in the central Arctic Ocean. MOSAiC would not have been possible without the logistic support provided by the AARI (Source: AWI Bremerhaven)

succeeded - with substanaltial international support in particular from Russia and Norway - to organize a one year drifting expedition to the central Arctic Ocean with the aim to collect atmospheric, hydrologic, glaciological and biological data from all seasons, as had been done though with much more modest means from Fridtjof Nansens Fram and from the Russian North Pole station program (Frolov et al., 2005). The leading scientist of the MOSAiC-expedition has recently published a comprehensive popular book (in German) about his experiences from the expedition (Rex, 2020) and about the "lessons learned" from this huge international enterprise which involved hundreds of scientists from 20 nations. Both Akademik Fedоrov and Akademik Tryoshnikov have helped Russian scientists to collect a wealth of geoscientific data from the central Arctic Ocean (Nikishin et al., 2021).

When scientific sea-floor drilling came to the Arctic Ocean

The geophysical and geological properties of the seafloor beyond the level of conventional sediment cores can only be elucidated by means of drilling into the seafloor with the aim to acquire sediment or rock cores. Dynamic positioning of drill ships is very difficult because of the drifting sea ice; but despite forseeable technical problems drilling Arctic seafloors was high on the agenda of the international community of geologists and geophysicists (NAD Science Committee, 1992). It is therefore that the Arctic seafloors are undersampled by this method as compared to any other subbasin of the world ocean, but three successful attempts can be listed up to now and a fourth will probably follow in 2022.

During IODP Leg 151 (Myhre, Thiede, Firth and Shipboard Scientific Party, 1995) the Joides Resolution, the scientific drill ship of the International Ocean Drilling Program and assisted by the Finnish heavy duty Icebreaker Fennica was able to enter the Arctic Ocean over the Yermak Plateau. An extension of the Norwegian Current generates a region of ice-free waters close to the ice margin allowing a drill ship dynamic positioning for drilling. Major results of this expedition were the recognition of an ice-shelf which extended over the Yermak Plateau during the latest Cenozoic, and the documentation of an ice age climate back into the Oligocene.

In 2000 a small geotechnical drill ship from Murmansk was able to visit the Laptev Sea shelf where seismic reflection profiles had indicated the presence of submarine permafrost (Kassens et al., 2001). At two drill sites the Holocene sediment cover was penetrated and sediment cores with remains of permafrost ice were recovered. Later dating showed that the permafrost had formed during the last glacial maximum (Kassens et al., 2007).

After the successful acquisition of seismic reflection across some of the structural highs in the central Arctic Ocean drilling plans were formulated and in 2004 the ACEX expedition (IODP Leg 302) to locations over the Lomonosov Ridge in the vicinity of the North Pole was organized (Fig. 13). The ships, the drilling platform Vidar Viking, accompanied by the Swedish icebreaker Oden and the Russian nuclear icebreaker Sovjetsky Sojus reached the desired locations which had been planned based on seismic reflection profiles collected in 1991 by Polarstern and which suggested that the crest of Lomonosov Ridge was covered by a several hundred meter thick undisturbed sediment sequence hopefully containing the record of the Cenozoic paleoenviromental history of the central Arctic Ocean. Several sites were drilled and the expectations of the scientific highly rewarded (Backman et al., 2006). The recovered sedimentary sequence documented the onset of Northern hemisphere glaciations approx. 48 ma. However, the stratigraphy of the drilled sites showed extended gaps (hiatus) covering much of the Oligocene and Miocene. Therefore another drilling campaign of similar locations, but closer to the Siberian continental margin is planned for the late summer 2022 with the aim to recover complete late Paleogene and Neogene stratigraphies (IODP Expedition 377 - ArcOP - Arctic Paleoceanography) again involving a drilling platform, protected and accompanied by heavy duty icebreakers.

And what comes next? And in the future?

The present generation of research ice breakers (Oden, Polarstern, Healy, Russian icebreakers) active in the central Arctic is ageing and needs to be retired and/or replaced, but decisions are not easy because of the high expenses; it remains to be seen if these highly successful, but expensive ships

Fig. 13. Armada of ice breakers and a drill ship during the ECORD expedition 2004 (Backman et al., 2006) to the Lomonosov Ridge. The Swedish drilling platform Reidar Viking in the foreground, the Swedish Oden in the center and the Russian nuclear icebreaker Sovjetsky Sojus in the distance (Source: ECORD 2004)

will be replaced one by one. Smaller dedicated research vessels adapted to work in the ice marginal zone have been built in a number of countries (Norway, US, Germany, some Asian countries).

Russia is following a different route, understandably because of its high stakes in the Arctic. It has taken into service the two research ice breakers Akademik Fedоrov and Akademik Tryoshnikov of the AARI (cf, Figs. 11 and 12) which have been contributing to international projects in many highly successful ways. They are also expanding their fleet of heavy duty icebreakers (many with nuclear propulsion systems) to serve on the Northern Sea Route.

Russia has a long and proud tradition to man scientific drifting stations on the sea ice of the central Arctic Ocean (Frolov et al., 2005) with most of them deployed through air planes. The program of opening and maintaining these stations (North Pole stations, NP-1 in 1937) was conducted over several decades, only interrupted during the second world war. It ended in 2015 after deploying a total of 41 NP-stations because the shrinking ice cover did not provide for safe locations any more. The scientific program of the stations included complex meteorological, oceanographic, glaciological, geophysical and sometimes biological observations (Frolov et al., 2005). The stations were manned mostly by Russian specialists and international members of the expeditions teams were an exception.

Fig. 14. The new Russian ice drift platform Severny Polyus/Ivan Frolov presently

being built in St. Petersburg, once it will be completed (Source: Roshydromet)

However, the Russian polar scientists have not given up the idea to establish technologies which will allow for scientific data collection during all seasons of the year. Having realized how important the NP-station data were for understanding the environmental dynamics of the central and southeastern Arctic Ocean, the AARI is reverting to the idea of deploying a new floating platform as the basis to continue this program (cf. Fig. 14). The "ship" is presently under construction in St. Petersburg and will be named Ivan Frolov, the former director of the AARI, who died in 2020. It will offer an important advantage to Russian polar research as compared to most other nations.

Conclusions

-The time span since 1980 comprised a revolution in marine polar research, in particular in the high northern latitudes;

-It was a time when the second generation of dedicated polar research vessels, came into use, mostly large and powerful icebreakers, with enough space for complex international expeditions, sophisticated laboratories serving a multitude of scientific disciplines, and sufficient power to handle heavy instruments;

-While the "summer" in the Arctic was well sampled, the unfavorable seasons were undersampled until quite recently. This will only change slowly, but the construction of the new Ivan Frolov of the AARI on the long run will hopefully be the nucleus for a network of such stations covering simultaneously several of the Arctic basins;

-From the slow progress in Arctic deep-sea drilling it is also clear that new data will be gained by the planned IODP expedition in 2022, but again it is only

targeting Cenozoic sedimentary sequences and leaves the exciting Mesozoic history of the central Arctic Ocean and many of the structural / tectonic problems untouched leading hopefully to increased scientific drilling activities in the future.

Acknowledgements

Much of the YMER-80 scientific program has been developed during a workshop on "Eastern Arctic Science" in Lyngby / Copenhagen 1979 which resulted in a Workshop Report published in 1980 by the Commission for Scientific Work in Greenland (edited by P. Gudmandsen). The rapid progress in polar marine research has been facilitated by international science organizations and the recognition of the impacts of the high latitude seas on the global climate and environment. We acknowledge with great gratitude the role of the government of the Russian Federation, which has favored this development of international cooperations. Also none of the scientific successes could have been achieved without the efforts of the institutions providing the icebreakers and without the efforts of their highly motivated crews.

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