Freshwater export from the south-east Greenland shelf into the Irminger Sea and relation to wind events

2021 ◽  
Author(s):  
Elodie Duyck ◽  
Femke De Jong
Keyword(s):  
Surface Water ◽  
Ekman Transport ◽  
The Arctic ◽  
The South ◽  
Overturning Circulation ◽  
East Greenland ◽  
East Greenland Current ◽  
Irminger Sea ◽  
Freshwater Export ◽  
Wind Events

<p>Greenland Ice Sheet melt and freshening of the Arctic Ocean lead to increased discharge of freshwater into the East Greenland Current. If this additional freshwater reaches the convective regions of the Subpolar North Atlantic it could weaken deep mixing and affect the strength of the Atlantic Meridional Overturning Circulation. In particular, freshwater exported away from the South-East Greenland shelf could affect deep convection in the Irminger Sea, which has recently been shown to have a key role in the Atlantic overturning circulation. Though export of fresh shelf surface water is well observed west of Greenland, there is still little insight into surface water export from the East Greenland shelf to the Irminger Sea.</p><p>The East Greenland Current Drifter Investigation of Freshwater Transport drifter deployment conducted in August 2019 at 65°N on the eastern side of Greenland, resulted in five out of 30 drifters being exported away from the east Greenland shelf, four of which were exported at Cape Farewell. The specific wind regime at Cape Farewell is a potential driving factor for enhanced freshwater export in the area. While persistent south-eastward barrier winds push surface waters to the coast over most of the eastern shelf, Cape Farewell experiences strong eastward wind events such as tip-jets that could cause off-shelf export. Using wind data from the ERA-5 atmospheric reanalysis, we compute Ekman transport along the east Greenland shelf. We find greater probability for off-shelf Ekman transport at Cape Farewell than along the rest of the shelf, confirming that the area is the most likely to contribute to wind-driven freshwater export to the Irminger Sea. Wind and surface velocity data from a high-resolution model (2 km) are used to further investigate and quantify freshwater export at Cape Farewell and how it relates to local wind events.</p>

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.

Tritium in the Arctic Ocean and East Greenland Current

1976 ◽  
Vol 32 (2) ◽  
pp. 342-350 ◽  
Author(s):  
H.G. Dorsey ◽  
W.H. Peterson
Keyword(s):  
Arctic Ocean ◽  
The Arctic ◽  
East Greenland ◽  
East Greenland Current ◽  
The Arctic Ocean

scholarly journals Origin and Composition of Seasonal Labrador Sea Freshwater

2007 ◽  
Vol 37 (6) ◽  
pp. 1445-1454 ◽  
Author(s):  
Sunke Schmidt ◽  
Uwe Send
Keyword(s):  
Time Scales ◽  
Late Summer ◽  
The Arctic ◽  
Labrador Sea ◽  
The West ◽  
East Greenland ◽  
West Greenland ◽  
Boundary Currents ◽  
East Greenland Current ◽  
West Greenland Current

Abstract The depth of winter convection in the central Labrador Sea is strongly influenced by the prevailing stratification in late summer. For this late summer stratification salinity is as important as temperature, and in the upper water layers salinity even dominates. To analyze the source of the spring and summer freshening in the central region, seasonal freshwater cycles have been constructed for the interior Labrador Sea, the West Greenland Current, and the Labrador Current. It is shown that none of the local freshwater sources is responsible for the spring–summer freshening in the interior, which appears to occur in two separate events in April to May and July to September. Comparing the timing and volume estimates of the seasonal freshwater cycles of the boundary currents with the central Labrador Sea helps in understanding the origin of the interior freshwater signals. The first smaller pulse cannot be attributed clearly to either of the boundary currents. The second one is about three times stronger and supplies 60% of the seasonal summer freshwater. Transport estimates and calculated mixing properties provide evidence that its source is the West Greenland Current. The finding implies a connection also on interannual time scales between Labrador Sea surface salinity and freshwater sources in the West Greenland Current and farther upstream in the East Greenland Current. The freshwater input from the West Greenland Current thus also is the likely pathway for the known modulation of Labrador Sea Water mass formation by freshwater export from the Arctic (via the East Greenland Current), which implies some predictability on longer time scales.

Microbial responses to the release of DOC by sea ice and glacier melting in the East Greenland System

2020 ◽  
Author(s):  
Alba Filella Lopez de Lamadrid ◽  
Anja Engel
Keyword(s):  
Ocean Circulation ◽  
Atlantic Water ◽  
The Arctic ◽  
Coastal System ◽  
East Greenland ◽  
East Greenland Current ◽  
Enhanced Production ◽  
Denmark Strait ◽  
Variable Environments ◽  
Microbial Responses

<p>Freshwater discharge around Greenland has more than doubled during the last decade. Understanding the associated physical and biogeochemical impacts in the ocean is of great importance for future predictions of ocean circulation, productivity and feedbacks within the Earth system. In summer 2019 we performed several cross-shore sections passing through the highly variable environments and physical regimes along the east Greenland coastline. Microbial communities showed distinct latitudinal and meridional distributions. Water mass characteristics played a major role in controlling the abundances of organisms with few groups appearing in significant numbers in coastal (colder and fresher) waters. Surface polar waters rich in dissolved organic carbon (DOC) flow south in the East Greenland Current maintaining a high DOC signal in inshore waters. Further optical analyses on the DOC fraction will determine what fractions of this material originate from long scale transport out of the Arctic. Of particular interest was an enhanced production of gel particles rich in carbon in an area extending across Denmark Strait, from close to Scoresby Sund to north of Iceland. Significant concentrations (e.g. 80 µg X.G. eq. L<sup>-1</sup>) of these transparent exopolymer particles (TEP) were even found deeper than 100m, which is highly unusual. Given the role of TEP as a binding agent for sinking particles, enhancing the sinking of carbon in the water column, it is of interest to know why such a TEP hotspot arises. We hypothesize that it could be either related to circulation through the Strait or the timing of bloom dynamics in this region prior to our cruise.  Our main conclusion from preliminary data analysis is that the east Greenland coastal system is highly dynamic with mixed properties reflecting various degrees of mixing between southward flowing Polar Water and warmer Atlantic water masses.</p>

scholarly journals A Regional Thermohaline Inverse Method for Estimating Circulation and Mixing in the Arctic and Subpolar North Atlantic

2018 ◽  
Vol 35 (12) ◽  
pp. 2383-2403 ◽  
Author(s):  
Neill Mackay ◽  
Chris Wilson ◽  
Jan Zika ◽  
N. Penny Holliday
Keyword(s):  
North Atlantic ◽  
Inverse Method ◽  
Surface Fluxes ◽  
Meridional Overturning Circulation ◽  
The Arctic ◽  
Surface Boundary ◽  
The South ◽  
Overturning Circulation ◽  
Transformation Rates ◽  
Meridional Overturning

AbstractA regional thermohaline inverse method (RTHIM) is presented that estimates velocities through the section bounding an enclosed domain and transformation rates resulting from interior mixing within the domain, given inputs of surface boundary fluxes of heat and salt and interior distributions of salinity and temperature. The method works by invoking a volumetric balance in thermohaline coordinates between the transformation resulting from mixing, surface fluxes, and advection, and constraining the mixing to be down tracer gradients. The method is validated using a 20-yr mean of outputs from the NEMO model in an Arctic and subpolar North Atlantic domain, bound to the south by a section with a mean latitude of 66°N. RTHIM solutions agree well with the NEMO model “truth” and are robust to a range of parameters; the meridional overturning circulation (MOC), heat, and freshwater transports calculated from an ensemble of RTHIM solutions are within 12%, 10%, and 19%, respectively, of the NEMO values. There is also bulk agreement between RTHIM solution transformation rates resulting from mixing and those diagnosed from NEMO. Localized differences in diagnosed mixing may be used to guide the development of mixing parameterizations in models such as NEMO, whose downgradient diffusive closures with prescribed diffusivity may be considered oversimplified and too restrictive.

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

2018 ◽  
Author(s):  
Maren Elisabeth Richter ◽  
Wilken-Jon von Appen ◽  
Claudia Wekerle
Keyword(s):  
Arctic Ocean ◽  
Atlantic Water ◽  
Ocean Model ◽  
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 Fram Strait. There the AAW is joined by recirculating AW. Here we present the first summer synoptic study targeted at resolving this confluence in 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 shelfbreak, 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 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-shelfbreak density gradient. This barotropic to baroclinic transition appears to form the well-known EGC boundary current flowing along the shelfbreak further south where it has been previously described. In this realization, between 80.2° N and 76.5° N, the southward transport along the east Greenland shelfbreak increases from roughly 1 Sv to about 4 Sv and the warm water composition, defined as the fraction of AW of the sum of AW and AAW (AW/(AW + AAW)), changes from 19 ± 8 % to 80 ± 3 %. Consequently, in southern Fram Strait, AW can propagate into 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.

scholarly journals Freshwater Export in the East Greenland Current Freshens the North Atlantic

2018 ◽  
Vol 45 (24) ◽  
Author(s):  
L. Steur ◽  
C. Peralta‐Ferriz ◽  
O. Pavlova
Keyword(s):  
North Atlantic ◽  
East Greenland ◽  
The North ◽  
East Greenland Current ◽  
The North Atlantic ◽  
Freshwater Export

scholarly journals On the Cascading of Dense Shelf Waters in the Irminger Sea

2012 ◽  
Vol 42 (12) ◽  
pp. 2254-2267 ◽  
Author(s):  
Anastasia Falina ◽  
Artem Sarafanov ◽  
Herlé Mercier ◽  
Pascale Lherminier ◽  
Alexey Sokov ◽  
...  
Keyword(s):  
Continental Slope ◽  
Western Boundary ◽  
Boundary Current ◽  
East Greenland ◽  
Low Salinity ◽  
East Greenland Current ◽  
Irminger Sea ◽  
Deep Western Boundary Current ◽  
Deep Waters ◽  
Denmark Strait

Abstract Hydrographic data collected in the Irminger Sea in the 1990s–2000s indicate that dense shelf waters carried by the East Greenland Current south of the Denmark Strait intermittently descend (cascade) down the continental slope and merge with the deep waters originating from the Nordic Seas overflows. Repeat measurements on the East Greenland shelf at ~200 km south of the Denmark Strait (65°–66°N) reveal that East Greenland shelf waters in the Irminger Sea are occasionally as dense (σ0 > 27.80) as the overflow-derived deep waters carried by the Deep Western Boundary Current (DWBC). Clear hydrographic traces of upstream cascading of dense shelf waters are found over the continental slope at 64.3°N, where the densest plumes (σ0 > 27.80) originating from the shelf are identified as distinct low-salinity anomalies in the DWBC. Downstream observations suggest that dense fresh waters descending from the shelf in the northern Irminger Sea can be distinguished in the DWBC up to the latitude of Cape Farewell (~60°N) and that these waters make a significant contribution to the DWBC transport.

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