scholarly journals The Atlantic Water boundary current in the Nansen Basin: Transport and mechanisms of lateral exchange

2016 ◽  
Vol 121 (9) ◽  
pp. 6946-6960 ◽  
Author(s):  
Kjetil Våge ◽  
Robert S. Pickart ◽  
Vladimir Pavlov ◽  
Peigen Lin ◽  
Daniel J. Torres ◽  
...  
Keyword(s):  
Atlantic Water ◽  
Boundary Current ◽  
Lateral Exchange

Topographically trapped waves along the continental slope north of Svalbard

2020 ◽  
Author(s):  
Kjersti Kalhagen ◽  
Frank Nilsen ◽  
Ragnheid Skogseth ◽  
Ilker Fer ◽  
Zoé Koenig ◽  
...  
Keyword(s):  
Heat Exchange ◽  
Arctic Ocean ◽  
Continental Slope ◽  
Atlantic Water ◽  
The Arctic ◽  
Boundary Current ◽  
Trapped Waves ◽  
Current Time ◽  
The Arctic Ocean ◽  
Lateral Exchange

<p>On the continental slope north of Svalbard, Atlantic Water is transported eastward as a part of the Arctic Circumpolar Boundary Current. As inflow of Atlantic Water through the Fram Strait is the largest oceanic heat source to the Arctic Ocean, it is important to improve our knowledge about the dynamics and processes that govern the heat exchange between Atlantic Water and water masses of Arctic origin. This includes processes that enable lateral exchange across the shelf break or into the interior of the deep basin. Here, we study the vorticity dynamics on the slope and its contribution to the water mass modifications and heat exchange. Focusing on topographically trapped waves – sub-inertial oscillations trapped to follow the continental slope – we establish their existence and properties on the northern slope of Svalbard using a free baroclinic wave model. Their dependence on background stratification and current properties is explored in sensitivity analysis. Next, we discuss their contribution to lateral exchange from the boundary current on the slope to the continental shelf, troughs, and the deep Nansen Basin in the Arctic Ocean, including exchange associated with instabilities and resulting eddy shedding off the vorticity waves. Hydrographic and current time series from 2018-19 at two mooring arrays crossing the slope north of Svalbard (The Nansen Legacy project) are used to associate the observed physical environment with model-predicted topographic waves. Analysis of the in-situ data will determine which wave mode that can exist over the sloping seafloor and the observed hydrography and flow, and the model will give the corresponding spatial characteristics for the given frequencies and wave numbers. Energetic oscillations present in the observations are analyzed in light of the model results. Of special interest are the seasonal variability in hydrography and current strength and the resulting modification of the wave characteristics. Moreover, the interaction between the vorticity waves and tidal oscillations in the diurnal band is emphasized.</p>

scholarly journals The Atlantic Water Boundary Current in the Chukchi Borderland and Southern Canada Basin

2020 ◽  
Vol 125 (8) ◽  
Author(s):  
Jianqiang Li ◽  
Robert S. Pickart ◽  
Peigen Lin ◽  
Frank Bahr ◽  
Kevin R. Arrigo ◽  
...  
Keyword(s):  
Atlantic Water ◽  
Canada Basin ◽  
Boundary Current ◽  
Chukchi Borderland

scholarly journals Structure, Transport, and Seasonality of the Atlantic Water Boundary Current North of Svalbard: Results From a Yearlong Mooring Array

2019 ◽  
Vol 124 (3) ◽  
pp. 1679-1698 ◽  
Author(s):  
M. Dolores Pérez‐Hernández ◽  
Robert S. Pickart ◽  
Daniel J. Torres ◽  
Frank Bahr ◽  
Arild Sundfjord ◽  
...  
Keyword(s):  
Atlantic Water ◽  
Boundary Current

scholarly journals Does the East Greenland Current exist in the northern Fram Strait?

Ocean Science ◽  
2018 ◽  
Vol 14 (5) ◽  
pp. 1147-1165 ◽  
Author(s):  
Maren Elisabeth Richter ◽  
Wilken-Jon von Appen ◽  
Claudia Wekerle
Keyword(s):  
Arctic Ocean ◽  
Atlantic Water ◽  
Shelf Break ◽  
The Arctic ◽  
Current Loop ◽  
Fram Strait ◽  
Boundary Current ◽  
East Greenland ◽  
East Greenland Current ◽  
The Arctic Ocean

Abstract. Warm Atlantic Water (AW) flows around the Nordic Seas in a cyclonic boundary current loop. Some AW enters the Arctic Ocean where it is transformed to Arctic Atlantic Water (AAW) before exiting through the Fram Strait. There the AAW is joined by recirculating AW. Here we present the first summer synoptic study targeted at resolving this confluence in the Fram Strait which forms the East Greenland Current (EGC). Absolute geostrophic velocities and hydrography from observations in 2016, including four sections crossing the east Greenland shelf break, are compared to output from an eddy-resolving configuration of the sea ice–ocean model FESOM. Far offshore (120 km at 80.8∘ N) AW warmer than 2 ∘C is found in the northern Fram Strait. The Arctic Ocean outflow there is broad and barotropic, but gets narrower and more baroclinic toward the south as recirculating AW increases the cross-shelf-break density gradient. This barotropic to baroclinic transition appears to form the well-known EGC boundary current flowing along the shelf break farther south where it has been previously described. In this realization, between 80.2 and 76.5∘ N, the southward transport along the east Greenland shelf break increases from roughly 1 Sv to about 4 Sv and the proportion of AW to AAW also increases fourfold from 19±8 % to 80±3 %. Consequently, in the southern Fram Strait, AW can propagate into the Norske Trough on the east Greenland shelf and reach the large marine-terminating glaciers there. High instantaneous variability observed in both the synoptic data and the model output is attributed to eddies, the representation of which is crucial as they mediate the westward transport of AW in the recirculation and thus structure the confluence forming the EGC.

Atlantic water north of Svalbard 1899-2018

2020 ◽  
Author(s):  
Marika Marnela ◽  
Frank Nilsen ◽  
Ragnheid Skogseth ◽  
Kjersti Kalhagen
Keyword(s):  
Historical Data ◽  
Saline Water ◽  
Atlantic Water ◽  
The Arctic ◽  
Boundary Current ◽  
Shelf Slope ◽  
Mean Width ◽  
Vertical Location ◽  
The Mean ◽  
West Spitsbergen

<p>As part of the Nansen Legacy project, waters north of Svalbard are studied. The warm and saline Atlantic water, brought northward by the West Spitsbergen Current cools and freshens as it flows eastward along the slope north of Svalbard, bringing heat and salt into the Arctic Ocean. Hydrographic CTD data are available from various cruises and databases, the main source here being the UNIS Hydrographic Database. Changes in the Atlantic water properties and its horizontal and vertical location on the slope and shelf are mapped from decadal averages of historical data from 1899 to 2018. The mean width of the boundary current following the slope eastward is estimated for five cross-shelf/slope sections from the decadal averages. An Atlantification is present from 1996-2005 to 2006-2018 with warmer and more saline water covering a larger area across the slope and reaching further east.</p>

scholarly journals The Atlantic Water boundary current north of Svalbard in late summer

2017 ◽  
Vol 122 (3) ◽  
pp. 2269-2290 ◽  
Author(s):  
M. Dolores Pérez-Hernández ◽  
Robert S. Pickart ◽  
Vladimir Pavlov ◽  
Kjetil Våge ◽  
Randi Ingvaldsen ◽  
...  
Keyword(s):  
Late Summer ◽  
Atlantic Water ◽  
Boundary Current

scholarly journals On the Circulation of Atlantic Water in the Arctic Ocean

2013 ◽  
Vol 43 (11) ◽  
pp. 2352-2371 ◽  
Author(s):  
Michael A. Spall
Keyword(s):  
Heat Flux ◽  
Numerical Model ◽  
Arctic Ocean ◽  
Surface Heat Flux ◽  
Atlantic Water ◽  
Surface Heat ◽  
The Arctic ◽  
Analytic Model ◽  
Boundary Current ◽  
The Arctic Ocean

Abstract An idealized eddy-resolving numerical model and an analytic three-layer model are used to develop ideas about what controls the circulation of Atlantic Water in the Arctic Ocean. The numerical model is forced with a surface heat flux, uniform winds, and a source of low-salinity water near the surface around the perimeter of an Arctic basin. Despite this idealized configuration, the model is able to reproduce many general aspects of the Arctic Ocean circulation and hydrography, including exchange through Fram Strait, circulation of Atlantic Water, a halocline, ice cover and transport, surface heat flux, and a Beaufort Gyre. The analytic model depends on a nondimensional number, and provides theoretical estimates of the halocline depth, stratification, freshwater content, and baroclinic shear in the boundary current. An empirical relationship between freshwater content and sea surface height allows for a prediction of the transport of Atlantic Water in the cyclonic boundary current. Parameters typical of the Arctic Ocean produce a cyclonic boundary current of Atlantic Water of O(1 − 2 Sv; where 1 Sv ≡ 106 m3 s−1) and a halocline depth of O(200 m), in reasonable agreement with observations. The theory compares well with a series of numerical model calculations in which mixing and environmental parameters are varied, thus lending credibility to the dynamics of the analytic model. In these models, lateral eddy fluxes from the boundary and vertical diffusion in the interior are important drivers of the halocline and the circulation of Atlantic Water in the Arctic Ocean.

scholarly journals Modified Halocline Water over the Laptev Sea Continental Margin: Historical Data Analysis

2012 ◽  
Vol 25 (16) ◽  
pp. 5556-5565 ◽  
Author(s):  
Igor A. Dmitrenko ◽  
Sergey A. Kirillov ◽  
Vladimir V. Ivanov ◽  
Bert Rudels ◽  
Nuno Serra ◽  
...  
Keyword(s):  
Continental Margin ◽  
North Atlantic Ocean ◽  
Source Region ◽  
Vertical Mixing ◽  
Atlantic Water ◽  
Laptev Sea ◽  
Boundary Current ◽  
Salinity Stratification ◽  
The North ◽  
The Laptev Sea

Abstract Historical hydrographic data (1940s–2010) show a distinct cross-slope difference of the lower halocline water (LHW) over the Laptev Sea continental margins. Over the slope, the LHW is on average warmer and saltier by 0.2°C and 0.5 psu, respectively, relative to the off-slope LHW. The LHW temperature time series constructed from the on-slope historical records are related to the temperature of the Atlantic Water (AW) boundary current transporting warm water from the North Atlantic Ocean. In contrast, the on-slope LHW salinity is linked to the sea ice and wind forcing over the potential upstream source region in the Barents and northern Kara Seas, as also indicated by hydrodynamic model results. Over the Laptev Sea continental margin, saltier LHW favors weaker salinity stratification that, in turn, contributes to enhanced vertical mixing with underlying AW.

scholarly journals Heat, salt, and volume transports in the eastern Eurasian Basin of the Arctic Ocean, from two years of mooring observations

2018 ◽  
Author(s):  
Andrey Pnyushkov ◽  
Igor Polyakov ◽  
Robert Rember ◽  
Vladimir Ivanov ◽  
Matthew B. Alkire ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Heat Transport ◽  
Atlantic Water ◽  
Salt Transport ◽  
The Arctic ◽  
Boundary Current ◽  
The Arctic Ocean ◽  
Eurasian Basin ◽  
The Laptev Sea ◽  
Volume Transports

Abstract. This study discusses along-slope volume, heat, and salt transports derived from observations collected in 2013–15 using a cross-slope array of six moorings ranging from 250 m to 3900 m in the eastern Eurasian Basin (EB) of the Arctic Ocean. These observations demonstrate that in the upper 780 m layer, the along-slope boundary current advected, on average, 5.1 ± 0.1 Sv of water, predominantly in the eastward (shallow-to-right) direction. Monthly net volume transports across the Laptev Sea slope vary widely, from ~ 0.3 ± 0.8 in April 2014 to ~ 9.9 ± 0.8 Sv in June 2014. 3.1 ± 0.1 Sv (or 60 %) of the net transport was associated with warm and salty intermediate-depth Atlantic Water (AW). Calculated heat transport for 2013–15 (relative to −1.8 °C) was 46.0 ± 1.7 TW, and net salt transport (relative to zero salinity) was 172 ± 6 Mkg/s. Estimates for AW heat and salt transports were 32.7 ± 1.3 TW (71 % of net heat transport) and 112 ± 4 Mkg/s (65 % of net salt transport). The variability of currents explains ~ 90 % of the variability of the heat and salt transports. The remaining ~ 10 % is controlled by temperature and salinity anomalies together with temporal variability of the AW layer thickness. The annual mean volume transports decreased by 25 % from 5.8 ± 0.2 Sv in 2013–14 to 4.4 ± 0.2 Sv in 2014–15 suggesting that changes of the transports at interannual and longer time scales in the eastern EB may be significant.

Warm core mesoscale eddies along the boundary current and in the Sofia Deep north of Svalbard

2021 ◽  
Author(s):  
Eivind H. Kolås ◽  
Kjersti Kalhagen ◽  
Zoe Koenig ◽  
Ilker Fer ◽  
Frank Nilsen
Keyword(s):  
Mesoscale Eddies ◽  
Atlantic Water ◽  
The Arctic ◽  
Boundary Current ◽  
Lateral Transport ◽  
Model Simulations ◽  
Warm Core ◽  
Intraseasonal Variations ◽  
The Arctic Ocean ◽  
Initial Results

<p>The Atlantic water boundary current north of Svalbard is a major heat and salt source to the Arctic Ocean. Yet, the mechanisms controlling the lateral transport of Atlantic water properties are not well understood. Model simulations suggest mesoscale eddies may be important for transporting heat away from the boundary current, but supporting observations are sparse.</p><p>Between September and November in 2018, a Seaglider was deployed north of Svalbard as part of the Nansen Legacy project to investigate intraseasonal variations in the boundary current and the transformation of Atlantic water. It made several transects across the boundary current and a transect across the Sofia deep. Warm core eddies originating from the boundary current were detected in the Sofia deep. Combining the Seaglider data with two year-long mooring arrays north of Svalbard, deployed in 2018 within the Nansen Legacy framework, we investigate mesoscale eddies using eddy recognition algorithms applied to glider transects and timeseries from moorings. Initial results indicate that mesoscale eddies frequently occur in the boundary current, with radius less than 10 km and velocity maxima as high as 0.35 m/s.</p>

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