The coherence of the oceanic heat transport through the Nordic seas: oceanic heat budget and interannual variability

Abstract. Atlantic Water is the main source of the heat and salt in the Arctic. On the way to the Arctic Ocean via the Nordic Seas, it interacts and mixes with other water masses which affects sea ice extent and deep water formation. The Atlantic Water heat transported into the Nordic Seas has a significant impact on the local climate and is investigated here along with its inter-annual variability using the ARMOR3D dataset, which is a collection of 3D monthly temperature, salinity and geostrophic velocities fields, derived from in situ and satellite data on a regular grid since 1993. The study region includes the eastern part of the Nordic seas, i.e., seven latitudinal transects from Svinoy section (65° N) to the northern part of the Fram Strait (78.8° N). The Atlantic Water heat advection decreases northwards, as a significant amount of heat is lost to the atmosphere and due to mixing with surrounding waters. As observed, the imbalance of heat fluxes in the upper layer leads to an increase in the upper ocean mean temperature over most of the study region. The correlations of the interannual variations of the advective heat fluxes rapidly drop from Svinoy to Jan Mayen sections and between Bear Island and Sorkapp sections. This is a result of a differential damping of periodicities (the 2–3 year and 5–6 year oscillations), as well as of different signs of the tendencies over the latest decades. The heat fluxes at all sections show a consistent change with meridional (C) and western (W) weather types, which is due to the different direction of the Ekman pumping associated with each of the weather types. A certain link to the NAO, AO and EA atmospheric indices is observed only at the southern sections.

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Early Spring Oceanic Heat Fluxes and Mixing Observed from Drift Stations North of Svalbard*

Journal of Physical Oceanography ◽

10.1175/2009jpo4172.1 ◽

2009 ◽

Vol 39 (12) ◽

pp. 3049-3069 ◽

Cited By ~ 40

Author(s):

Anders Sirevaag ◽

Ilker Fer

Keyword(s):

Mixed Layer ◽

Heat Budget ◽

Atlantic Water ◽

Early Spring ◽

Heat Fluxes ◽

Eddy Correlation ◽

The Arctic ◽

Water Current ◽

Turbulent Heat ◽

Turbulent Characteristics

Abstract From several drifting ice stations north of Svalbard, Norway, observations were made in early spring of the ocean turbulent characteristics in the upper 150 m using a microstructure profiler and close to the under-ice surface using eddy correlation instrumentation. The dataset is used to obtain average heat fluxes at the ice–water interface, in the mixed layer, across the main pycnocline, as well over different water masses in the region. The results are contrasted with proximity to the branches of the warm and saline Atlantic water current, the West Spitsbergen Current (WSC), which is the main oceanic heat and salinity source both to the region and to the Arctic Ocean. Hydrographic properties show that the surface water mass modification is typically due to atmospheric cooling with relatively less influence of ice melting. Surface heat fluxes of O(100) W m−2 are found within the branches of the WSC and over shelf areas with elevated levels of mixing due to strong tides. Away from the shelves and WSC, however, ocean-to-ice turbulent heat fluxes are typical of the central Arctic. Deeper in the water column, entrainment from below together with equally important horizontal advection and diffusion increase the heat content of the mixed layer and contribute to the heat flux maximum in the upper layers. The results in this study emphasize the importance of mixing along the boundaries, over shelves, and topography for the cooling of the Atlantic water layer in the Arctic in general, and for the regional heat budget, hence the ice cover and cooling of the WSC north of Svalbard, in particular.

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Eastern Arctic Ocean Diapycnal Heat Fluxes through Large Double-Diffusive Steps

Journal of Physical Oceanography ◽

10.1175/jpo-d-18-0080.1 ◽

2019 ◽

Vol 49 (1) ◽

pp. 227-246 ◽

Cited By ~ 5

Author(s):

Igor V. Polyakov ◽

Laurie Padman ◽

Y.-D. Lenn ◽

Andrey Pnyushkov ◽

Robert Rember ◽

...

Keyword(s):

Arctic Ocean ◽

Dissipation Rate ◽

Critical Role ◽

Density Ratio ◽

Atlantic Water ◽

Heat Fluxes ◽

The Arctic ◽

Eurasian Basin ◽

Average Flux ◽

Double Diffusive

AbstractThe diffusive layering (DL) form of double-diffusive convection cools the Atlantic Water (AW) as it circulates around the Arctic Ocean. Large DL steps, with heights of homogeneous layers often greater than 10 m, have been found above the AW core in the Eurasian Basin (EB) of the eastern Arctic. Within these DL staircases, heat and salt fluxes are determined by the mechanisms for vertical transport through the high-gradient regions (HGRs) between the homogeneous layers. These HGRs can be thick (up to 5 m and more) and are frequently complex, being composed of multiple small steps or continuous stratification. Microstructure data collected in the EB in 2007 and 2008 are used to estimate heat fluxes through large steps in three ways: using the measured dissipation rate in the large homogeneous layers; utilizing empirical flux laws based on the density ratio and temperature step across HGRs after scaling to account for the presence of multiple small DL interfaces within each HGR; and averaging estimates of heat fluxes computed separately for individual small interfaces (as laminar conductive fluxes), small convective layers (via dissipation rates within small DL layers), and turbulent patches (using dissipation rate and buoyancy) within each HGR. Diapycnal heat fluxes through HGRs evaluated by each method agree with each other and range from ~2 to ~8 W m−2, with an average flux of ~3–4 W m−2. These large fluxes confirm a critical role for the DL instability in cooling and thickening the AW layer as it circulates around the eastern Arctic Ocean.

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

10.5194/egusphere-egu21-14798 ◽

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

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 &#8216;Arctic Amplification&#8217;. 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.

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Regularities and features of ice conditions of the Barents Sea in the second half of XX – early XXI century

10.29006/978-5-6045110-0-8/(15) ◽

2021 ◽

pp. 179-194

Author(s):

I.O. Dumanskaya ◽

Keyword(s):

Barents Sea ◽

Ice Cover ◽

Heat Fluxes ◽

The Arctic ◽

Cycle Period ◽

Arctic Seas ◽

Sea Ice Extent ◽

The Barents Sea ◽

Western Border ◽

Quantitative Changes

The warming of the Arctic, especially intensified at the beginning of the XXI century, is accompanied by a significant decrease in the area of ice cover in the Arctic seas. The article shows the quantitative changes in the ice parameters of the Barents Sea, as well as factors affecting the formation of ice cover in recent years. In the twenty-first century the frequency of occurrence of mild winters has increased by 17%, the frequency of severe winters has decreased by 19%. Significantly increased the temperature at the meteorological station Malye Karmakuly, water temperature at transect "Kola Meridian", atmospheric and oceanic heat fluxes, and speed of sea currents on the Western border of the Barents sea. The duration of the ice period decreased by an average of 2–3 weeks, and the rate of reduction of ice cover was 7.2% for 10 years. This is the highest speed compared to other Arctic seas. The article shows that the variability of the ice cover of the Barents Sea and other parameters of the natural environment in the region has the cyclic character. Presumably, the cycle period is close to 84 years, which corresponds to the orbital period of Uranium. The minimum sea ice extent after 1935–1945 is expected in the period 2019–2029.

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Circulation and transformation of Atlantic water in the Eurasian Basin and the contribution of the Fram Strait inflow branch to the Arctic Ocean heat budget

Progress In Oceanography ◽

10.1016/j.pocean.2014.04.003 ◽

2015 ◽

Vol 132 ◽

pp. 128-152 ◽

Cited By ~ 59

Author(s):

Bert Rudels ◽

Meri Korhonen ◽

Ursula Schauer ◽

Sergey Pisarev ◽

Benjamin Rabe ◽

...

Keyword(s):

Arctic Ocean ◽

Heat Budget ◽

Atlantic Water ◽

The Arctic ◽

Fram Strait ◽

The Arctic Ocean ◽

Eurasian Basin

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Frontal structures in the West Spitsbergen Current margins

Ocean Science ◽

10.5194/os-9-957-2013 ◽

2013 ◽

Vol 9 (6) ◽

pp. 957-975 ◽

Cited By ~ 52

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.

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Heat content in the Norwegian Sea, 1995–2010

ICES Journal of Marine Science ◽

10.1093/icesjms/fss026 ◽

2012 ◽

Vol 69 (5) ◽

pp. 826-832 ◽

Cited By ~ 26

Author(s):

Øystein Skagseth ◽

Kjell Arne Mork

Keyword(s):

Heat Content ◽

Atlantic Water ◽

Heat Fluxes ◽

Gradual Transition ◽

Absolute Maximum ◽

Nordic Seas ◽

Norwegian Sea ◽

Ocean Climate ◽

The North ◽

Spatio Temporal

Abstract Skagseth, Ø., and Mork, K. A. 2012. Heat content in the Norwegian Sea, 1995–2010. – ICES Journal of Marine Science, 69: 826–832. Spatio-temporal hydrographic data from the Nordic Seas during spring over the period 1995–2010 were investigated in terms of the relative heat content (RHC) above the density surface σt = 27.9, chosen to capture the changes in Atlantic water (AW). Focusing on the Atlantic (eastern) domain of the Nordic Seas, negative anomalies dominated the early part of the series. There was then a gradual transition towards an absolute maximum in 2003/2004, followed by a small reduction with positive values for the period ending in 2010. The maps clearly reveal the events of propagating signals. The variability is regionally comparable, but the persistence on a year-to-year basis is higher in the Lofoten Basin than in the Norwegian Basin. Compared with other studies, in this study, the estimated trend in the RHC of the Nordic Seas was larger than for the global mean and the North Atlantic. The warming of the Nordic Seas derives mainly from the advection of warmer inflowing AW and less from changes in local air–sea heat fluxes. The importance of advection suggests that the variability of the Norwegian Sea's ocean climate can, to a large extent, be predicted based on the observed hydrographic conditions.

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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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The Arctic–Atlantic Thermohaline Circulation*

Journal of Climate ◽

10.1175/jcli-d-13-00305.1 ◽

2013 ◽

Vol 26 (21) ◽

pp. 8698-8705 ◽

Cited By ~ 23

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.

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

10.5194/egusphere-egu2020-10513 ◽

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

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 (SSH) biases in the Nordic Seas. We argue 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 by atmospheric origins.

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