Freshwater pulses in the eastern Arctic Ocean during Saalian and Early Weichselian ice-sheet collapse

AbstractImproved multiparameter records from the northern Barents Sea margin show two prominent freshwater pulses into the Arctic Ocean during MIS 5 that significantly disturbed the regional oceanic regime and probably affected global climate. Both pulses are associated with major iceberg-rafted debris (IRD) events, revealing intensive iceberg/sea ice melting. The older meltwater pulse occurred near the MIS 5/6 boundary (∼131,000 yr ago); its ∼2000 year duration and high IRD input accompanied by high illite content suggest a collapse of large-scale Saalian Glaciation in the Arctic Ocean. Movement of this meltwater with the Transpolar Drift current into the Fram Strait probably promoted freshening of Nordic Seas surface water, which may have increased sea-ice formation and significantly reduced deep-water formation. A second pulse of freshwater occurred within MIS 5a (∼77,000 yr ago); its high smectite content and relatively short duration is possibly consistent with sudden discharge of Early Weichselian ice-dammed lakes in northern Siberia as suggested by terrestrial glacial geologic data. The influence of this MIS 5a meltwater pulse has been observed at a number of sites along the Transpolar Drift, through Fram Strait, and into the Nordic Seas; it may well have been a trigger for the North Atlantic cooling event C20.

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A satellite-based Lagrangian perspective on Atlantic Water fractionation in the Nordic Seas

10.5194/egusphere-egu2020-8422 ◽

2020 ◽

Author(s):

Léon Chafik ◽

Sara Broomé

Keyword(s):

Arctic Ocean ◽

Barents Sea ◽

Bottom Topography ◽

Atlantic Water ◽

The Arctic ◽

Fram Strait ◽

Nordic Seas ◽

The Barents Sea ◽

The Arctic Ocean ◽

Outer Branch

The Arctic Ocean has been receiving&#160;more of the warm and saline Atlantic Water in the past&#160;decades. This water mass enters the Arctic Ocean via two Arctic gateways: the Barents Sea Opening and the Fram Strait.&#160;Here, we focus on the fractionation of Atlantic Water at these two gateways using a Lagrangian approach based on satellite-derived geostrophic velocities.&#160;Simulated particles are released at 70N at the inner and outer branch of the North Atlantic current system&#160;in the Nordic Seas. The trajectories toward the Fram Strait and Barents Sea Opening&#160;are found to be&#160;largely steered by the bottom topography and there is an indication of an&#160;anti-phase relationship in the number of particles reaching the gateways. There is, however, a significant&#160;cross-over of particles from the outer branch to the inner branch and into the Barents Sea, which is&#160;found to be related to high eddy kinetic energy between the branches. This cross-over may be important for Arctic climate variability.

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Unprecedented decline of sea ice thickness in Fram Strait in 2017-2018

10.5194/egusphere-egu21-6427 ◽

2021 ◽

Author(s):

Hiroshi Sumata ◽

Laura de Steur ◽

Dmitry Divine ◽

Olga Pavlova ◽

Sebastian Gerland

Keyword(s):

Sea Ice ◽

Arctic Ocean ◽

Barents Sea ◽

North Atlantic Ocean ◽

The Arctic ◽

Ice Thickness ◽

Fram Strait ◽

Sea Ice Thickness ◽

Drift Speed ◽

The Arctic Ocean

Fram Strait is the major gateway connecting the Arctic Ocean and the northern North Atlantic Ocean where about 80 to 90% of sea ice outflow from the Arctic Ocean takes place. Long-term observations from the Fram Strait Arctic Outflow Observatory maintained by the Norwegian Polar Institute captured an unprecedented decline of sea ice thickness in 2017 &#8211; 2018 since comprehensive observations started in the early 1990s. Four Ice Profiling Sonars moored in the East Greenland Current in Fram Strait simultaneously recorded 50 &#8211; 70 cm decline of annual mean ice thickness in comparison with preceding years. A backward trajectory analysis revealed that the decline was attributed to an anomalous sea level pressure pattern from 2017 autumn to 2018 summer. Southerly wind associated with a dipole pressure anomaly between Greenland and the Barents Sea prevented southward motion of ice floes north of Fram Strait. Hence ice pack was exposed to warm Atlantic Water in the north of Fram Strait 2 &#8211; 3 times longer than the average year, allowing more melt to happen. At the same time, the dipole anomaly was responsible for the slowest observed annual mean ice drift speed in Fram Strait in the last two decades. As a consequence of the record minimum of ice thickness and the slowest drift speed, the sea ice volume transport through the Fram Strait dropped by more than 50% in comparison with the 2010 &#8211; 2017 average.

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Arctic Ocean circulation and variability – advection and external forcing encounter constraints and local processes

Ocean Science Discussions ◽

10.5194/osd-8-2313-2011 ◽

2011 ◽

Vol 8 (6) ◽

pp. 2313-2376 ◽

Cited By ~ 2

Author(s):

B. Rudels

Keyword(s):

Sea Ice ◽

Arctic Ocean ◽

Ocean Circulation ◽

Barents Sea ◽

Atlantic Water ◽

The Arctic ◽

Fram Strait ◽

Intermediate Layers ◽

The Arctic Ocean ◽

Almost All

Abstract. The first hydrographic data from the Arctic Ocean, the section from the Laptev Sea to the passage between Greenland and Svalbard obtained by Nansen on the drift by Fram 1893–1896, aptly illustrate the main features of Arctic Ocean oceanography and indicate possible processes active in transforming the water masses in the Arctic Ocean. Many, perhaps most, of these processes were identified already by Nansen, who put his mark on almost all subsequent research in the Arctic Ocean. Here we shall revisit some key questions and follow how our understanding has evolved from the early 20th century to present. What questions, if any, can now be regarded as solved and which remain still open? Five different but connected topics will be discussed: (1) The low salinity surface layer and the storage and export of freshwater. (2) The vertical heat transfer from the Atlantic water to sea ice and to the atmosphere. (3) The circulation and mixing of the two Atlantic inflow branches. (4) The formation and circulation of deep and bottom waters in the Arctic Ocean. (5) The exchanges through Fram Strait. Foci will be on the potential effects of increased freshwater input and reduced sea ice export on the freshwater storage and residence time in the Arctic Ocean, on the deep waters of the Makarov Basin and on the circulation and relative importance of the two inflows, over the Barents Sea and through Fram Strait, for the distribution of heat in the intermediate layers of the Arctic Ocean.

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Pacific Water Pathways through the Arctic Ocean

10.5194/egusphere-egu2020-15898 ◽

2020 ◽

Author(s):

Paul A. Dodd ◽

Tore Hattermann ◽

Michael Karcher ◽

Frank Kauker ◽

Colin Stedmon

Keyword(s):

Sea Ice ◽

Arctic Ocean ◽

Large Scale ◽

The Arctic ◽

Fram Strait ◽

Bering Strait ◽

Wind Fields ◽

Pacific Water ◽

Back Trajectories ◽

The Arctic Ocean

The volume, characteristics and sources of freshwater circulating in the Arctic Ocean vary in time and are expected to change under a declining sea ice cover, influencing the physical environment and Arctic ecosystem. Relatively fresh (S = 32) Pacific Water, which enters the Arctic Ocean via the Bering Strait makes up a significant part of the liquid freshwater exiting the Arctic Ocean through Fram Strait. If transported to the Nordic Seas and North Atlantic via the East- and West Greenland Currents freshwater from the Pacific could have an effect on convection and dense water formation in those regions.More than 30 repeated sections of nutrient measurements have been collected across Fram Strait between 1980 and 2019. The fraction of Pacific Water along these repeated sections can be estimated from the ratio of nitrate to phosphate. The time-series of repeated Fram Strait sections indicates that the fraction of Pacific Water passing out of the Arctic Ocean has changed significantly over the last 30 years. Pacific water fractions remained high from 1980 to 1998, but in 1999 Pacific water almost disappeared from Fram Strait, reappearing from 2011 to 2012, when there was a peak in freshwater export though Fram Strait.Several hypotheses suggest how variations in the large-scale atmospheric circulation over the Arctic Ocean may influence the transport and pathways of Pacific Water. We show how anomalies in reanalysis wind fields are associated with the reappearance of Pacific Water in Fram Strait in recent years. Repeated sections across Fram Strait are compared with sea ice back-trajectories in the Polar Pathfinder 4 product and a simulated Pacific Water tracer in the NAOSIM numerical model to investigate likely Pacific water pathways through the Arctic Ocean and upstream drivers of changes observed in Fram Strait.

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Arctic Ocean circulation and variability – advection and external forcing encounter constraints and local processes

Ocean Science ◽

10.5194/os-8-261-2012 ◽

2012 ◽

Vol 8 (2) ◽

pp. 261-286 ◽

Cited By ~ 70

Author(s):

B. Rudels

Keyword(s):

Sea Ice ◽

Arctic Ocean ◽

Ocean Circulation ◽

Barents Sea ◽

Atlantic Water ◽

The Arctic ◽

Fram Strait ◽

Intermediate Layers ◽

The Arctic Ocean ◽

Almost All

Abstract. The first hydrographic data from the Arctic Ocean, the section from the Laptev Sea to the passage between Greenland and Svalbard obtained by Nansen on his drift with Fram 1893–1896, aptly illustrate the main features of Arctic Ocean oceanography and indicate possible processes active in transforming the water masses in the Arctic Ocean. Many, perhaps most, processes were identified already by Nansen, who put his mark on almost all subsequent research in the Arctic. Here we shall revisit some key questions and follow how our understanding has evolved from the early 20th century to present. What questions, if any, can now be regarded as solved and which remain still open? Five different but connected topics will be discussed: (1) The low salinity surface layer and the storage and export of freshwater. (2) The vertical heat transfer from the Atlantic water to sea ice and to the atmosphere. (3) The circulation and mixing of the two Atlantic inflow branches. (4) The formation and circulation of deep and bottom waters in the Arctic Ocean. (5) The exchanges through Fram Strait. Foci will be on the potential effects of increased freshwater input and reduced sea ice export on the freshwater storage and residence time in the Arctic Ocean, on the deep waters of the Makarov Basin, and on the circulation and relative importance of the two inflows, over the Barents Sea and through Fram Strait, for the distribution of heat in the intermediate layers of the Arctic Ocean.

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Simulated Variability of the Arctic Ocean Freshwater Balance 1948–2001

Journal of Physical Oceanography ◽

10.1175/jpo3063.1 ◽

2007 ◽

Vol 37 (6) ◽

pp. 1628-1644 ◽

Cited By ~ 22

Author(s):

Cornelia Köberle ◽

Rüdiger Gerdes

Keyword(s):

Sea Ice ◽

Arctic Ocean ◽

Barents Sea ◽

The Arctic ◽

Freshwater Flux ◽

Fram Strait ◽

The Arctic Ocean ◽

The 1960S ◽

Freshwater Balance ◽

Volume Transports

Abstract The Arctic Ocean freshwater balance over the period 1948–2001 is examined using results from a hindcast simulation with an ocean–sea ice model of the Atlantic and Arctic Oceans. Atmospheric forcing is taken from the NCEP–NCAR reanalysis and different terrestrial freshwater sources as well as the Bering Strait throughflow are specified as constant seasonal cycles. The long-term variability of the Arctic Ocean liquid freshwater content is determined by the variability of lateral exchanges with the subpolar seas. Surface freshwater flux variability is dominated by the thermodynamic growth of sea ice. This component of the freshwater balance has larger variability at interannual frequencies. The Arctic Ocean liquid freshwater content was at a maximum in the middle of the 1960s. Extremely low liquid freshwater export through Fram Strait caused this maximum in the freshwater content. The low export rate was related to weak volume transports in the East Greenland Current. Low volume transports were forced by a reduction in sea surface height across Fram Strait, triggered by anomalous meltwater from Barents Sea ice export that was carried toward Fram Strait with the West Spitzbergen Current. After the 1960s maximum liquid freshwater content, the Arctic Ocean gradually returned to an equilibrium between export through the passages toward the Atlantic and the freshwater sources.

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Cryospheric Impacts of Soviet River Diversion Schemes

Annals of Glaciology ◽

10.3189/1984aog5-1-61-68 ◽

1984 ◽

Vol 5 ◽

pp. 61-68 ◽

Cited By ~ 4

Author(s):

T. Holt ◽

P. M. Kelly ◽

B. S. G. Cherry

Keyword(s):

Sea Ice ◽

Arctic Ocean ◽

River Discharge ◽

Large Scale ◽

Arctic Sea Ice ◽

The Arctic ◽

Sea Ice Concentration ◽

Ice Concentration ◽

The Arctic Ocean ◽

The Impact

Soviet plans to divert water from rivers flowing into the Arctic Ocean have led to research into the impact of a reduction in discharge on Arctic sea ice. We consider the mechanisms by which discharge reductions might affect sea-ice cover and then test various hypotheses related to these mechanisms. We find several large areas over which sea-ice concentration correlates significantly with variations in river discharge, supporting two particular hypotheses. The first hypothesis concerns the area where the initial impacts are likely to which is the Kara Sea. Reduced riverflow is associated occur, with decreased sea-ice concentration in October, at the time of ice formation. This is believed to be the result of decreased freshening of the surface layer. The second hypothesis concerns possible effects on the large-scale current system of the Arctic Ocean and, in particular, on the inflow of Atlantic and Pacific water. These effects occur as a result of changes in the strength of northward-flowing gradient currents associated with variations in river discharge. Although it is still not certain that substantial transfers of riverflow will take place, it is concluded that the possibility of significant cryospheric effects and, hence, large-scale climate impact should not be neglected.

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