A Diagnostic Model of the Nordic Seas and Arctic Ocean Circulation: Quantifying the Effects of a Variable Bottom Density along a Sloping Topography

Abstract A linear diagnostic model, solving for the time-mean large-scale circulation in the Nordic seas and Arctic Ocean, is presented. Solutions on depth contours that close within the Nordic seas and Arctic Ocean are found from vorticity balances integrated over the areas enclosed by the contours. Climatological data for wind stress and hydrography are used as input to the model, and the bottom geostrophic flow is assumed to follow depth contours. Comparison against velocity observations shows that the simplified dynamics in the model capture many aspects of the large-scale circulation. Special attention is given to the dynamical effects of an along-isobath varying bottom density, which leads to a transformation between barotropic and baroclinic transport. Along the continental slope, enclosing both the Nordic seas and Arctic Ocean, the along-slope barotropic transport has a maximum in the Nordic seas and a minimum in the Canadian Basin with a difference of 9 Sv (1 Sv ≡ 106 m3 s−1) between the two. This is caused by the relatively lower bottom densities in the Canadian Basin compared to the Nordic seas and suggests that most of the barotropic transport entering the Arctic Ocean through the Fram Strait is transformed to baroclinic transport. A conversion from barotropic to baroclinic flow may be highly important for the slope–basin exchange in the Nordic seas and Arctic Ocean. The model has obvious shortcomings due to its simplicity. However, the simplified physics and the agreement with observations make this model an excellent framework for understanding the large-scale circulation in the Nordic seas and Arctic Ocean.

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Large-scale temperature and salinity changes in the upper Canadian basin of the Arctic Ocean at a time of a drastic Arctic Oscillation inversion

Ocean Science Discussions ◽

10.5194/osd-9-2001-2012 ◽

2012 ◽

Vol 9 (3) ◽

pp. 2001-2038 ◽

Cited By ~ 1

Author(s):

P. Bourgain ◽

J. C. Gascard ◽

J. Shi ◽

J. Zhao

Keyword(s):

Arctic Ocean ◽

Large Scale ◽

Arctic Oscillation ◽

Atlantic Water ◽

The Arctic ◽

Near Surface ◽

Beaufort Gyre ◽

Pacific Waters ◽

The Pacific ◽

Canadian Basin

Abstract. Between 2008 and 2010, the Arctic Oscillation index over Arctic regions shifted from positive values corresponding to more cyclonic conditions prevailing during IPY period (2007–2008) to extremely negative values corresponding to strong anticyclonic conditions in 2010. In this context, we investigated the recent large scale evolution of the upper Western Arctic Ocean based on temperature and salinity summertime observations collected during icebreaker campaigns and from Ice-Tethered Platforms (ITP) drifting across the region in 2008 and 2010. Particularly, we focused on (1) the freshwater content which was extensively studied during previous years, (2) the Near Surface Temperature Maximum due to incoming solar radiation and (3) the water masses advected from the Pacific and Atlantic Oceans into the deep Arctic Ocean. The observations revealed a freshwater content change in the Canadian basin during this time period. South of 80° N, the freshwater content increased, while north of 80° N, less freshening occurred in 2010 compared to 2008. This was more likely due to the strong anticyclonicity characteristic of a low AO index mode that enhanced both a wind-generated Ekman pumping in the Beaufort Gyre and a diversion of the Siberian rivers runoff toward the Eurasian basin at the same time. The Near Surface Temperature Maximum due to incoming solar radiation was almost 1 °C colder in the Southern Canada basin (south of 75° N) in 2010 compared to 2008 which contrasted with the positive trend observed during previous years. This was more likely due to higher summer sea ice concentration in 2010 compared to 2008 in that region, and surface albedo feedback reflecting more sun radiation back in space. The Pacific waters were also subjected to strong spatial and temporal variability between 2008 and 2010. In the Canada basin, both Summer and Winter Pacific waters influence increased between 75° N and 80° N. This was more likely due to a strong recirculation within the Beaufort Gyre. In contrast, south of 75° N, the PaW influence decreased indicative of the fact that they were not responsible for the freshening already mentioned, due to other sources. In addition, in the vicinity of the Chukchi Sea, both Summer and Winter Pacific waters were significantly warmer in 2010 than in 2008 as a consequence of a general warming trend of the Pacific waters entering in the deep Arctic Ocean since 2008. Finally, the warm Atlantic water remained relatively stable between 2008 and 2010 in the Canadian basin despite strong atmospheric shift, probably because of large time lag response. Atlantic water variability resulting from the presence of a warm "pulse-like" event in this region since 2005 was still noticeable even if a cooling effect was observed at a rate of 0.015 °C yr−1 between 2008 and 2010 in that region.

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

Quaternary Research ◽

10.1016/j.yqres.2003.07.008 ◽

2003 ◽

Vol 60 (3) ◽

pp. 243-251 ◽

Cited By ~ 26

Author(s):

Jochen Knies ◽

Christoph Vogt

Keyword(s):

Sea Ice ◽

Arctic Ocean ◽

Large Scale ◽

Barents Sea ◽

The Arctic ◽

Fram Strait ◽

Nordic Seas ◽

The Arctic Ocean ◽

Transpolar Drift ◽

Mis 5

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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The Norwegian node for the European Multidisciplinary Seafloor and water column Observatory

10.5194/egusphere-egu2020-7248 ◽

2020 ◽

Author(s):

Thibaut Barreyre ◽

Ilker Fer ◽

Bénédicte Ferré

Keyword(s):

Water Column ◽

Ocean Circulation ◽

Large Scale ◽

Water Mass ◽

Critical Role ◽

Meridional Overturning Circulation ◽

The Arctic ◽

Global Ocean ◽

Fram Strait ◽

Nordic Seas

NorEMSO is a coordinated, large-scale deep-ocean observation facility to establish the Norwegian node for the European Multidisciplinary Seafloor and water column Observatory (EMSO). The project aims to explore the under-sampled Nordic Seas to gain a better understanding of the critical role that they play in our climate system and global ocean circulation. An overarching scientific objective is to better understand the drivers for the temporal and spatial changes of water mass transformations, ocean circulation, acidification and thermo-chemical exchanges at the seafloor in the Nordic Seas, and to contribute to improvement of models and forecasting by producing and making available high quality, near real time data. NorEMSO will achieve this by combining expansion of existing and establishment of new observatory network infrastructure, as well as its coordination and integration into EMSO.NorEMSO comprises of three main components: moored observatories, gliders, and seafloor and water column observatory at the Mohn Ridge (EMSO-Mohn).Moored observation systems include an array of four moored observatories located at key positions in the Nordic Seas (Svin&#248;y, Station M, South Cape, and central Fram Strait).Gliders will be operated along five transects across both the Norwegian and the Greenland Seas to monitor circulation and water mass properties at those key locations. Transects in the Norwegian and Lofoten basins will focus on monitoring the Norwegian Atlantic Current, and a transect in Fram Strait will monitor properties and variability in the return Atlantic Water along the Polar Front in the northern Nordic Seas. In addition, transects in the Greenland and Iceland Seas will address the water mass transformation processes through wintertime open ocean convection, and the southbound transport of surface water from the Arctic Ocean and dense water that feeds the lower limb of the Atlantic Meridional Overturning Circulation in the East Greenland Current.EMSO-Mohn will establish, at the newly discovered hydrothermal site on the Mohn Ridge, a fixed-point seabed-water-column-coupled and wireless observatory with a multidisciplinary approach &#8211; from geophysics and physical oceanography to ecology and microbiology. It is primarily directed at understanding hydrothermal fluxes and associated hydrothermal plume dynamics in the water column and how it disperses in an oceanographic front over the Mohn Ridge.Following EMSO philosophy, NorEMSO will provide data and platforms to a large and diverse group of users, from scientists and industries to institutions and policy makers. The observations will serve climate research, ocean circulation understanding, numerical operational models, design of environmental policies, and education.

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Large-scale temperature and salinity changes in the upper Canadian Basin of the Arctic Ocean at a time of a drastic Arctic Oscillation inversion

Ocean Science ◽

10.5194/os-9-447-2013 ◽

2013 ◽

Vol 9 (2) ◽

pp. 447-460 ◽

Cited By ~ 10

Author(s):

P. Bourgain ◽

J. C. Gascard ◽

J. Shi ◽

J. Zhao

Keyword(s):

Solar Radiation ◽

Arctic Ocean ◽

Large Scale ◽

Arctic Oscillation ◽

The Arctic ◽

Near Surface ◽

Beaufort Gyre ◽

The Pacific ◽

The Arctic Ocean ◽

Canadian Basin

Abstract. Between 2008 and 2010, the Arctic Oscillation index over Arctic regions shifted from positive values corresponding to more cyclonic conditions prevailing during the 4th International Polar Year (IPY) period (2007–2008) to extremely negative values corresponding to strong anticyclonic conditions in 2010. In this context, we investigated the recent large-scale evolution of the upper western Arctic Ocean, based on temperature and salinity summertime observations collected during icebreaker campaigns and from ice-tethered profilers (ITPs) drifting across the region in 2008 and 2010. Particularly, we focused on (1) the freshwater content which was extensively studied during previous years, (2) the near-surface temperature maximum due to incoming solar radiation, and (3) the water masses advected from the Pacific Ocean into the Arctic Ocean. The observations revealed a freshwater content change in the Canadian Basin during this time period. South of 80° N, the freshwater content increased, while north of 80° N, less freshening occurred in 2010 compared to 2008. This was more likely due to the strong anticyclonicity characteristic of a low AO index mode that enhanced both a wind-generated Ekman pumping in the Beaufort Gyre and a possible diversion of the Siberian River runoff toward the Eurasian Basin at the same time. The near-surface temperature maximum due to incoming solar radiation was almost 1 °C colder in the southern Canada Basin (south of 75° N) in 2010 compared to 2008, which contrasted with the positive trend observed during previous years. This was more likely due to higher summer sea ice concentration in 2010 compared to 2008 in that region, and surface albedo feedback reflecting more sun radiation back in space. The Pacific water (PaW) was also subjected to strong spatial and temporal variability between 2008 and 2010. In the Canada Basin, both summer and winter PaW signatures were stronger between 75° N and 80° N. This was more likely due to a strong recirculation within the Beaufort Gyre. In contrast, south of 75° N, the cooling and warming of the summer and winter PaW, respectively, suggest that either the PaW was less present in 2010 than in 2008 in this region, and/or the PaW was older in 2010 than in 2008. In addition, in the vicinity of the Chukchi Sea, both summer and winter PaW were significantly warmer in 2010 than in 2008, as a consequence of a general warming trend of the PaW entering in the deep Arctic Ocean as of 2008.

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A study of the large scale circulation and water mass formation in the Nordic seas and Arctic ocean

10.1575/1912/5571 ◽

1993 ◽

Cited By ~ 10

Author(s):

Cecilie Mauritzen

Keyword(s):

Arctic Ocean ◽

Large Scale ◽

Water Mass ◽

Large Scale Circulation ◽

Nordic Seas ◽

Water Mass Formation ◽

Mass Formation

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On large-scale shifts in the Arctic Ocean and sea-ice conditions during 1979−98

Annals of Glaciology ◽

10.3189/172756401781818978 ◽

2001 ◽

Vol 33 ◽

pp. 545-550 ◽

Cited By ~ 35

Author(s):

W. Maslowski ◽

D. C. Marble ◽

W. Walczowski ◽

A. J. Semtner

Keyword(s):

Sea Ice ◽

Arctic Ocean ◽

Fresh Water ◽

Ocean Circulation ◽

Large Scale ◽

Atlantic Water ◽

The Arctic ◽

Upper Ocean ◽

Recent Climate ◽

The Arctic Ocean

AbstractResults from a regional model of the Arctic Ocean and sea ice forced with realistic atmospheric data are analyzed to understand recent climate variability in the region. The primary simulation uses daily-averaged 1979 atmospheric fields repeated for 20 years and then continues with interannual forcing derived from the European Centre for Medium-range Weather Forecasts for 1979−98. An eastward shift in the ice-ocean circulation, fresh-water distribution and Atlantic Water extent has been determined by comparing conditions between the early 1980s and 1990s. A new trend is modeled in the late 1990s, and has a tendency to return the large-scale sea-ice and upper ocean conditions to their state in the early 1980s. Both the sea-ice and the upper ocean circulation as well as fresh-water export from the Russian shelves and Atlantic Water recirculation within the Eurasian Basin indicate that the Arctic climate is undergoing another shift. This suggests an oscillatory behavior of the Arctic Ocean system. Interannual atmospheric variability appears to be the main and sufficient driver of simulated changes. The ice cover acts as an effective dynamic medium for vorticity transfer from the atmosphere into the ocean.

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Large-scale circulation and water mass distribution in the Arctic Ocean from model results and observations

Journal of Geophysical Research Atmospheres ◽

10.1029/97jc00102 ◽

1997 ◽

Vol 102 (C4) ◽

pp. 8467-8483 ◽

Cited By ~ 27

Author(s):

Rüdiger Gerdes ◽

Ursula Schauer

Keyword(s):

Arctic Ocean ◽

Mass Distribution ◽

Large Scale ◽

Water Mass ◽

The Arctic ◽

Large Scale Circulation ◽

The Arctic Ocean

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A changing Arctic Ocean: How measured and modeled 129I distributions indicate fundamental shifts in circulation between 1994 and 2015

10.5194/egusphere-egu21-7198 ◽

2021 ◽

Author(s):

Michael J. Karcher ◽

John N. Smith ◽

Núria Casacuberta ◽

William J. Williams ◽

Tim Kenna ◽

...

Keyword(s):

Arctic Ocean ◽

Ocean Circulation ◽

Large Scale ◽

The Arctic ◽

Strong Increase ◽

Climate Indices ◽

Data Sets ◽

Boundary Current ◽

The Arctic Ocean ◽

Atlantic Origin

129I measurements on samples collected during GEOTRACES oceanographic missions in the Arctic Ocean in 2015 have provided the first detailed, synoptic 129I sections across the Eurasian, Canada and Makarov Basins. 129I is discharged from European nuclear fuel reprocessing plants since several decades and is carried north into the Arctic Ocean with waters of Atlantic origin. Here the measurements of its passage can be used to identify the ocean circulation at different depth horizons. Elevated 129I levels measured over the Lomonosov and Alpha-Mendeleyev Ridges in 2015 were associated with tracer labeled, Atlantic-origin water bathymetrically steered by the ridge systems through the central Arctic while lower 129I levels were evident in the more poorly ventilated basin interiors. 129I levels of 200-400 x 107 at/l measured in intermediate waters had increased by a factor of 10 compared to results from the same locations in 1994-1996 owing to the arrival of a strong increase in the discharges from La Hague, that occurred during the 1990s. Comparisons of the patterns of 129I between the mid-1990s and 2015 delineate large scale circulation changes that occurred during the shift from a positive Arctic Oscillation and a cyclonic circulation regime in the mid-1990s to anticyclonic circulation in 2015. These are characterized by a broadened Beaufort Gyre in the upper ocean, a weakened boundary current and partial AW flow reversal in the southern Canada Basin at mid-depth. Tracer 129I simulations using the coupled ocean-sea ice model NAOSIM agree with both, the historical 129I results and recent GEOTRACES data sets, thereby lending context and credibility to the interpretation of large-scale changes in Arctic circulation and their relationship to shifts in climate indices revealed by the tracer 129I distributions. We will present measurements and simulation results of 129I for the 1990s and 2015 and put them into the context of ocean circulation responses to changing atmospheric forcing regimes.

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