scholarly journals Heat Balance in the Nordic Seas in a Global 1/12° Coupled Model

2021 ◽  
Vol 34 (1) ◽  
pp. 89-106
Author(s):  
Anne Marie Treguier ◽  
Pierre Mathiot ◽  
Tim Graham ◽  
Dan Copsey ◽  
Camille Lique ◽  
...  
Keyword(s):  
Heat Transport ◽  
Heat Loss ◽  
Heat Balance ◽  
Coupled Model ◽  
Atlantic Water ◽  
Surface Fluxes ◽  
The Arctic ◽  
Knipovich Ridge ◽  
Current Time ◽  
Nordic Seas

AbstractThe Nordic seas are a gateway to the Arctic Ocean, where Atlantic water undergoes a strong cooling during its transit. Here we investigate the heat balance of these regions in the high-resolution Met Office Global Coupled Model GC3 with a 1/12° grid. The GC3 model reproduces the contrasted ice conditions and ocean heat loss between the eastern and western regions of the Nordic seas. In the west (Greenland and Iceland seas), the heat loss experienced by the ocean is stronger than the atmospheric heat gain, because of the cooling by ice melt. The latter is a major contribution to the heat loss over the path of the East Greenland Current and west of Svalbard. In the model, surface fluxes balance the convergence of heat in each of the eastern and western regions. The net east–west heat exchange, integrated from Fram Strait to Iceland, is relatively small: the westward heat transport of the Return Atlantic Current over Knipovich Ridge balances the eastward heat transport by the East Icelandic Current. Time fluctuations, including eddies, are a significant contribution to the net heat transports. The eddy flux represents about 20% of the total heat transport in Denmark Strait and across Knipovich Ridge. The coupled ocean–atmosphere–ice model may overestimate the heat imported from the Atlantic and exported to the Arctic by 10% or 15%. This confirms the tendency toward higher northward heat transports as model resolution is refined, which will impact scenarios of future climate.

scholarly journals Nordic Seas Heat Loss, Atlantic Inflow, and Arctic Sea Ice cover over the last century

2021 ◽  
Author(s):  
Lars H. Smedsrud ◽  
Morven Muilwijk ◽  
Ailin Brakstad ◽  
Erica Madonna ◽  
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Heat Transport ◽  
Heat Loss ◽  
The Arctic ◽  
Co2 Uptake ◽  
Ocean Heat Transport ◽  
Total Heat Loss ◽  
Nordic Seas

<p>Poleward ocean heat transport is a key process in the earth system. Here we detail the changing northward Atlantic Water (AW) flow in the Nordic Seas and the associated Arctic Ocean heat transport and heat loss to the atmosphere since 1900, in relation to the sea ice cover. Our synthesis is largely based on a sea ice-ocean model forced by a reanalysis atmosphere (1900-2018) corroborated by a comprehensive hydrographic database (1950-), measurements of AW inflow (1996-), and other key long-term regional time series. Since the 1970s, ocean temperatures have increased in the Nordic, Barents and Polar Seas, in particular on the shelves. The AW loses heat to the atmosphere as it travels poleward, mostly in  the Nordic Seas, where ~60% of the Arctic Ocean total heat loss resides. Nordic Seas heat loss variability is large, but the long-term positive trend is small. The Barents Sea heat loss is ~30% of the total, but has larger consistently positive trends, related to AW heat transport and sea ice loss. The Arctic seas farther north see only ~10% of the  total heat loss, but show a consistently large increase in heat loss as well as decrease in sea ice since 1900. The AW inflow, the cooling of this water mass as it travels poleward, and the dense outflow have thus all increased since 1900, and they are consistently related through theoretical scaling. Some of the increased AW inflow is wind-driven, and much of the heat loss variability is linked to Cold Air Outbreaks and cyclones in the Nordic and Barents Seas. The oceanic warming is congruent with increased ocean heat transport and a loss of sea ice, and has contributed to the retreat of marine terminating glaciers on Greenland. After 2000, the warming has accelerated, creating a “new normal” that appears to also affect deep water volumes and temperature. The 20th century average Nordic, Barents and Polar Seas CO2 uptake constitutes ~8% of the global ocean, and is almost entirely driven by heat loss to the atmosphere as the AW transforms from inflow to overflow water. The total Arctic Ocean CO2 uptake has increased by ~30% since 1900, which is closely linked to the loss of sea ice in the Barents and Polar Seas.</p>

scholarly journals Response of the Atlantic Thermohaline Circulation to Increased Atmospheric CO2 in a Coupled Model

2004 ◽  
Vol 17 (21) ◽  
pp. 4267-4279 ◽  
Author(s):  
Aixue Hu ◽  
Gerald A. Meehl ◽  
Warren M. Washington ◽  
Aiguo Dai
Keyword(s):  
Sea Ice ◽  
Heat Transport ◽  
North Atlantic ◽  
Thermohaline Circulation ◽  
Climate Model ◽  
Coupled Model ◽  
The Arctic ◽  
Labrador Sea ◽  
Upper Ocean ◽  
Gin Seas

Abstract Changes in the thermohaline circulation (THC) due to increased CO2 are important in future climate regimes. Using a coupled climate model, the Parallel Climate Model (PCM), regional responses of the THC in the North Atlantic to increased CO2 and the underlying physical processes are studied here. The Atlantic THC shows a 20-yr cycle in the control run, qualitatively agreeing with other modeling results. Compared with the control run, the simulated maximum of the Atlantic THC weakens by about 5 Sv (1 Sv ≡ 106 m3 s−1) or 14% in an ensemble of transient experiments with a 1% CO2 increase per year at the time of CO2 doubling. The weakening of the THC is accompanied by reduced poleward heat transport in the midlatitude North Atlantic. Analyses show that oceanic deep convective activity strengthens significantly in the Greenland–Iceland–Norway (GIN) Seas owing to a saltier (denser) upper ocean, but weakens in the Labrador Sea due to a fresher (lighter) upper ocean and in the south of the Denmark Strait region (SDSR) because of surface warming. The saltiness of the GIN Seas are mainly caused by an increased salty North Atlantic inflow, and reduced sea ice volume fluxes from the Arctic into this region. The warmer SDSR is induced by a reduced heat loss to the atmosphere, and a reduced sea ice flux into this region, resulting in less heat being used to melt ice. Thus, sea ice–related salinity effects appear to be more important in the GIN Seas, but sea ice–melt-related thermal effects seem to be more important in the SDSR region. On the other hand, the fresher Labrador Sea is mainly attributed to increased precipitation. These regional changes produce the overall weakening of the THC in the Labrador Sea and SDSR, and more vigorous ocean overturning in the GIN Seas. The northward heat transport south of 60°N is reduced with increased CO2, but increased north of 60°N due to the increased flow of North Atlantic water across this latitude.

Influence of Nordic Seas dynamics on the Atlantic Water propagation and its impacts on sea ice concentration.

2021 ◽  
Author(s):  
Sourav Chatterjee ◽  
Roshin P Raj ◽  
Laurent Bertino ◽  
Nuncio Murukesh
Keyword(s):  
Sea Ice ◽  
Deep Water ◽  
Atlantic Water ◽  
The Arctic ◽  
Deep Water Formation ◽  
Sea Ice Concentration ◽  
Nordic Seas ◽  
Ice Concentration ◽  
Water Formation

<p>Enhanced intrusion of warm and saline Atlantic Water (AW) to the Arctic Ocean (AO) in recent years has drawn wide interest of the scientific community owing to its potential role in ‘Arctic Amplification’. Not only the AW has warmed over the last few decades , but its transfer efficiency have also undergone significant modifications due to changes in atmosphere and ocean dynamics at regional to large scales. The Nordic Seas (NS), in this regard, play a vital role as the major exchange of polar and sub-polar waters takes place in this region. Further, the AW and its significant modification on its way to AO via the Nordic Seas has large scale implications on e.g., deep water formation, air-sea heat fluxes. Previous studies have suggested that a change in the sub-polar gyre dynamics in the North Atlantic controls the AW anomalies that enter the NS and eventually end up in the AO. However, the role of NS dynamics in resulting in the modifications of these AW anomalies are not well studied. Here in this study, we show that the Nordic Seas are not only a passive conduit of AW anomalies but the ocean circulations in the Nordic Seas, particularly the Greenland Sea Gyre (GSG) circulation can significantly change the AW characteristics between the entry and exit point of AW in the NS. Further, it is shown that the change in GSG circulation can modify the AW heat distribution in the Nordic Seas and can potentially influence the sea ice concentration therein. Projected enhanced atmospheric forcing in the NS in a warming Arctic scenario and the warming trend of the AW can amplify the role of NS circulation in AW propagation and its impact on sea ice, freshwater budget and deep water formation.</p>

scholarly journals Frontal structures in the West Spitsbergen Current margins

Ocean Science ◽  
2013 ◽  
Vol 9 (6) ◽  
pp. 957-975 ◽  
Author(s):  
W. Walczowski
Keyword(s):  
Thermohaline Circulation ◽  
Baroclinic Instability ◽  
Atlantic Water ◽  
Transport Processes ◽  
The Arctic ◽  
The West ◽  
Jet Streams ◽  
Nordic Seas ◽  
Western Border ◽  
West Spitsbergen

Abstract. The structures of the hydrographic fronts separating the Atlantic-origin waters from ambient waters in the northern Nordic Seas are discussed. Flows of the western and eastern branches of the West Spitsbergen Current create the Atlantic domain borders and maintain these fronts. This work is based on previous research and on investigations carried out in the project DAMOCLES (Developing Arctic Modelling and Observational Capabilities for Long-term Environmental Studies). Most of the observational data were collected during the R/V Oceania cruises. The main focus of the paper is the western border of the Atlantic domain – the Arctic Front, alongfrontal and transfrontal transports, and the front instability and variability. The alongfrontal baroclinic jet streams were described as a significant source of the Atlantic Water and heat in the Nordic Seas. The baroclinic instability and advection of baroclinic eddies which occurs due to this instability were found to be the main transfrontal transport processes. Most of the Atlantic Water transported by the western branch recirculates west and southward. The eastern branch of the West Spitsbergen Current provides most of the Atlantic Water entering the Arctic Ocean. Both processes are very important for the Arctic and global thermohaline circulation.

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

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

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

scholarly journals The Arctic–Atlantic Thermohaline Circulation*

2013 ◽  
Vol 26 (21) ◽  
pp. 8698-8705 ◽  
Author(s):  
Tor Eldevik ◽  
Jan Even Ø. Nilsen
Keyword(s):  
Degrees Of Freedom ◽  
Thermohaline Circulation ◽  
Global Climate ◽  
Atlantic Water ◽  
The Arctic ◽  
Freshwater Input ◽  
Future Change ◽  
Nordic Seas ◽  
Atlantic Thermohaline Circulation ◽  
Northern Branch

Abstract The Atlantic Ocean's thermohaline circulation is an important modulator of global climate. Its northern branch extends through the Nordic Seas to the cold Arctic, a region that appears to be particularly influenced by climate change. A thermohaline circulation is fundamentally concerned with two degrees of freedom. This is in particular the case for the inflow of warm and saline Atlantic Water through the Nordic Seas toward the Arctic that is balanced by two branches of outflow. The authors present an analytical model, rooted in observations, that constrains the strength and structure of this Arctic–Atlantic thermohaline circulation. It is found, maybe surprisingly, that the strength of Atlantic inflow is relatively insensitive to anomalous freshwater input; it mainly reflects changes in northern heat loss. Freshwater anomalies are predominantly balanced by the inflow's partition into estuarine and overturning circulation with southward polar outflow in the surface and dense overflow at depth, respectively. More quantitatively, the approach presented herein provides a relatively simple framework for making closed and consistent inference on the thermohaline circulation's response to observed or estimated past and future change in the northern seas.

Cold and Fresh Biases of the Arctic Atlantic Water Layer in CMIP6 Models; Potential Origin and Implications

2020 ◽  
Author(s):  
Narges Khosravi ◽  
Nikolay Koldunov ◽  
Qiang Wang ◽  
Sergery Danilov ◽  
Claudia Hinrichs ◽  
...  
Keyword(s):  
Water Layer ◽  
Atlantic Water ◽  
The Arctic ◽  
Sea Level Pressure ◽  
Climate Signal ◽  
Nordic Seas ◽  
East Greenland Current ◽  
Gyre Circulation ◽  
Rule Out ◽  
Potential Origin

<p><span>We examined the Arctic Atlantic Water (AW) layer in the CMIP6 models. Climatological means of temperature and salinity at 400 m depth from multi-model averages are compared with observations, showing significant biases in both variables. Based on the currently available data, we showed that the CMIP6 models have cold and fresh biases in the Arctic AW layer, and warm and saline biases in the East Greenland Current. The temperature biases are comparable to the climate signal magnitude for temperature, predicted by the CMIP6 models for the end of the 21st century. For salinity, the biases are shown to be even more pronounced than the predicted signals. CMIP6 models also show positive sea-level pressure (SLP) and sea-surface height </span>(SSH) <span>biases in the Nordic Seas. </span>We argue <span>that the identified SLP bias leads to an anomalously weak cyclonic gyre circulation in the Nordic seas, as shown through positive SSH bias. This could cause weaker AW inflow through the Fram Strait, which explains the detected hydrography biases in the AW layer. While we do not rule out other possible factors contributing to the weak AW flow to the Arctic Ocean, we suggest that the identified ocean biases within the CMIP6 models are at least partially driven b</span>y<span> atmospheric origins.</span></p>

scholarly journals Winter Convection Transports Atlantic Water Heat to the Surface Layer in the Eastern Arctic Ocean*

2013 ◽  
Vol 43 (10) ◽  
pp. 2142-2155 ◽  
Author(s):  
Igor V. Polyakov ◽  
Andrey V. Pnyushkov ◽  
Robert Rember ◽  
Laurie Padman ◽  
Eddy C. Carmack ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Heat Loss ◽  
Mixed Layer ◽  
Atlantic Water ◽  
Velocity Shear ◽  
The Arctic ◽  
Ice Formation ◽  
Surface Mixed Layer ◽  
Winter Convection

Abstract A 1-yr (2009/10) record of temperature and salinity profiles from Ice-Tethered Profiler (ITP) buoys in the Eurasian Basin (EB) of the Arctic Ocean is used to quantify the flux of heat from the upper pycnocline to the surface mixed layer. The upper pycnocline in the central EB is fed by the upward flux of heat from the intermediate-depth (~150–900 m) Atlantic Water (AW) layer; this flux is estimated to be ~1 W m−2 averaged over one year. Release of heat from the upper pycnocline, through the cold halocline layer to the surface mixed layer is, however, seasonally intensified, occurring more strongly in winter. This seasonal heat loss averages ~3–4 W m−2 between January and April, reducing the rate of winter sea ice formation. This study hypothesizes that the winter heat loss is driven by mixing caused by a combination of brine-driven convection associated with sea ice formation and larger vertical velocity shear below the base of the surface mixed layer (SML), enhanced by atmospheric storms and the seasonal reduction in density difference between the SML and underlying pycnocline.

scholarly journals The Arctic Ocean Seasonal Cycles of Heat and Freshwater Fluxes: Observation-Based Inverse Estimates

2018 ◽  
Vol 48 (9) ◽  
pp. 2029-2055 ◽  
Author(s):  
Takamasa Tsubouchi ◽  
Sheldon Bacon ◽  
Yevgeny Aksenov ◽  
Alberto C. Naveira Garabato ◽  
Agnieszka Beszczynska-Möller ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Barents Sea ◽  
Numerical Models ◽  
Water Layer ◽  
Atlantic Water ◽  
Surface Fluxes ◽  
The Arctic ◽  
Bering Strait ◽  
The Arctic Ocean

AbstractThis paper presents the first estimate of the seasonal cycle of ocean and sea ice heat and freshwater (FW) fluxes around the Arctic Ocean boundary. The ocean transports are estimated primarily using 138 moored instruments deployed in September 2005–August 2006 across the four main Arctic gateways: Davis, Fram, and Bering Straits, and the Barents Sea Opening (BSO). Sea ice transports are estimated from a sea ice assimilation product. Monthly velocity fields are calculated with a box inverse model that enforces mass and salt conservation. The volume transports in the four gateways in the period (annual mean ± 1 standard deviation) are −2.1 ± 0.7 Sv in Davis Strait, −1.1 ± 1.2 Sv in Fram Strait, 2.3 ± 1.2 Sv in the BSO, and 0.7 ± 0.7 Sv in Bering Strait (1 Sv ≡ 106 m3 s−1). The resulting ocean and sea ice heat and FW fluxes are 175 ± 48 TW and 204 ± 85 mSv, respectively. These boundary fluxes accurately represent the annual means of the relevant surface fluxes. The ocean heat transport variability derives from velocity variability in the Atlantic Water layer and temperature variability in the upper part of the water column. The ocean FW transport variability is dominated by Bering Strait velocity variability. The net water mass transformation in the Arctic entails a freshening and cooling of inflowing waters by 0.62 ± 0.23 in salinity and 3.74° ± 0.76°C in temperature, respectively, and a reduction in density by 0.23 ± 0.20 kg m−3. The boundary heat and FW fluxes provide a benchmark dataset for the validation of numerical models and atmospheric reanalysis products.

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.

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