Assessment of the Atlantic water layer in the Arctic Ocean in CMIP5 climate models

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.

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Atlantic Water properties, transport, and water mass transformation north of Svalbard from one-year-long mooring observations

10.5194/egusphere-egu21-2505 ◽

2021 ◽

Author(s):

Zoé Koenig ◽

Kjersti Kalhagen ◽

Eivind Kolås ◽

Ilker Fer ◽

Frank Nilsen ◽

...

Keyword(s):

Arctic Ocean ◽

Water Layer ◽

Atlantic Water ◽

Water Inflow ◽

The Arctic ◽

Short Time Scale ◽

The Arctic Ocean ◽

Explained Variance ◽

One Year ◽

Counter Current

North of Svalbard is a key region for the Arctic Ocean heat and salt budget as it is the gateway for one of the main branches of Atlantic Water to the Arctic Ocean. As the Atlantic Water layer advances into the Arctic, its core deepens from about 250 m depth around the Yermak Plateau to 350 m in the Laptev Sea, and gets colder and less saline due to mixing with surrounding waters. The complex topography in the region facilitates vertical and horizontal exchanges between the water masses and, together with strong shear and tidal forcing driving increased mixing rates, impacts the heat and salt content of the Atlantic Water layer that will circulate around the Arctic Ocean.In September 2018, 6 moorings organized in 2 arrays were deployed across the Atlantic Water Boundary current for more than one year (until November 2019), within the framework of the Nansen Legacy project to investigate the seasonal variations of this current and the transformation of the Atlantic Water North of Svalbard. The Atlantic Water inflow exhibits a large seasonal signal, with maxima in core temperature and along-isobath velocities in fall and minima in spring. Volume transport of the Atlantic Water inflow varies from 0.7 Sv in spring to 3 Sv in fall. An empirical orthogonal function analysis of the daily cross-isobath temperature sections reveals that the first mode of variation (explained variance ~80%) is the seasonal cycle with an on/off mode in the temperature core. The second mode (explained variance ~ 15%) corresponds to a short time scale (less than 2 weeks) variability in the onshore/offshore displacement of the temperature core. On the shelf, a counter-current flowing westward is observed in spring, which transports colder (~ 1&#176;C) and fresher (~ 34.85 g kg-1) water than Atlantic Water (&#952; > 2&#176;C and SA > 34.9 g kg-1). The processes driving the dynamic of the counter-current are under investigation. At greater depth (~1000 m) on the offshore part of the slope, a bottom-intensified current is noticed that seems to covary with the wind stress curl. Heat loss of the Atlantic Water between the two mooring arrays is maximum in winter reaching 250 W m-2 when the current is the largest and the net radiative flux from the atmosphere to the ocean is the smallest (only 50 W m-2 compared to about 400 W m-2 in summer).

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Effect of vertical mixing on the Atlantic Water layer circulation in the Arctic Ocean

Journal of Geophysical Research Atmospheres ◽

10.1029/2006jc003732 ◽

2007 ◽

Vol 112 (C4) ◽

Cited By ~ 48

Author(s):

Jinlun Zhang ◽

Mike Steele

Keyword(s):

Arctic Ocean ◽

Vertical Mixing ◽

Water Layer ◽

Atlantic Water ◽

The Arctic ◽

The Arctic Ocean

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The Atlantic Water boundary current North of Svalbard in 2018-2019: background properties, dynamics and turbulence.

10.5194/egusphere-egu2020-6981 ◽

2020 ◽

Author(s):

Zoé Koenig ◽

Eivind Kolås ◽

Kjersti Kalhagen ◽

Ilker Fer

Keyword(s):

Arctic Ocean ◽

Water Column ◽

Mixed Layer ◽

Dissipation Rate ◽

Water Layer ◽

Atlantic Water ◽

The Arctic ◽

Boundary Current ◽

Turbulent Dissipation ◽

The Arctic Ocean

North of Svalbard is a key region for the Arctic Ocean heat and salt budget as it is the gateway for one of the main branches of Atlantic Water in the Arctic. As the Atlantic Water layer advances into the Arctic Ocean, its core deepens from about 250 m depth around the Yermak Plateau to 350 m in the Laptev Sea, and gets colder and less saline due to mixing with surrounding waters. The complex topography in the region facilitates vertical and horizontal exchanges between the water masses and, together with strong shear and tidal forcing driving increased mixing rates, impacts the heat and salt content of the Atlantic Water layer that will circulate the Arctic Ocean.In summer 2018, 6 moorings organized in 2 arrays were deployed across the Atlantic Water Boundary current for a year, within the framework of the Nansen Legacy project. In parallel, turbulence structure in the Atlantic Water boundary current was measured north of Svalbard in two different periods (July and September), using a Vertical Microstructure Profiler (Rockland Scientific) in both cruises and a Microrider (Rockland Scientific) mounted on a Slocum glider in September.Using mooring observations, we investigated the background properties of the Atlantic Water boundary current (transport, vertical structure, seasonal variations) and the possible sources of the low-frequency variations (period of more than 2 weeks). Using observations during the cruise periods, we investigated changes in the mixed layer through the summer and the sources of vertical mixing in the water column. In the mixed layer, depth-integrated turbulent dissipation rate is about 10-4 W m-2. Variations in the turbulent heat, salinity and buoyancy fluxes are strong, and hypothesized to be affected by the evolution of the surface meltwater layer through summer. When integrated over the Atlantic Water layer, the turbulent dissipation rate is about 3.10-3 W m-2. Whilst the wind work exerted in the mixed layer accounts for most of the variability in the mixed layer, tidal forcing plays an important role in setting the dissipation rates deeper in the water column.

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Temperature difference across the Lomonosov Ridge: Implications for the Atlantic Water circulation in the Arctic Ocean

Geophysical Research Letters ◽

10.1029/2005gl023982 ◽

2005 ◽

Vol 32 (20) ◽

Cited By ~ 14

Author(s):

Takashi Kikuchi

Keyword(s):

Arctic Ocean ◽

Temperature Difference ◽

Atlantic Water ◽

Water Circulation ◽

The Arctic ◽

Lomonosov Ridge ◽

The Arctic Ocean

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The role of sea ice for plastic pollution in the Arctic

10.5194/egusphere-egu21-13366 ◽

2021 ◽

Author(s):

Ilka Peeken ◽

Elisa Bergami ◽

Ilaria Corsi ◽

Benedikt Hufnagl ◽

Christian Katlein ◽

...

Keyword(s):

Sea Ice ◽

Arctic Ocean ◽

Long Range ◽

Environmental Concern ◽

Ice Cores ◽

Atlantic Water ◽

The Arctic ◽

Polar Regions ◽

Plastic Pollution ◽

The Arctic Ocean

Marine plastic pollution is a growing worldwide environmental concern as recent reports indicate that increasing quantities of litter disperse into secluded environments, including Polar Regions. Plastic degrades into smaller fragments under the influence of sunlight, temperature changes, mechanic abrasion and wave action resulting in small particles < 5mm called microplastics (MP). Sea ice cores, collected in the Arctic Ocean have so far revealed extremely high concentrations of very small microplastic particles, which might be transferred in the ecosystem with so far unknown consequences for the ice dependant marine food chain.&#160; Sea ice has long been recognised as a transport vehicle for any contaminates entering the Arctic Ocean from various long range and local sources. The Fram Strait is hereby both, a major inflow gateway of warm Atlantic water, with any anthropogenic imprints and the major outflow region of sea ice originating from the Siberian shelves and carried via the Transpolar Drift. The studied sea ice revealed a unique footprint of microplastic pollution, which were related to different water masses and indicating different source regions. Climate change in the Arctic include loss of sea ice, therefore, large fractions of the embedded plastic particles might be released and have an impact on living systems. By combining modeling of sea ice origin and growth, MP particle trajectories in the water column as well as MPs long-range transport via particle tracking and transport models we get first insights &#160;about the sources and pathways of MP in the Arctic Ocean and beyond and how this might affect the Arctic ecosystem.

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Intensification of the Atlantic Water Supply to the Arctic Ocean Through Fram Strait Induced by Arctic Sea Ice Decline

Geophysical Research Letters ◽

10.1029/2019gl086682 ◽

2020 ◽

Vol 47 (3) ◽

Cited By ~ 3

Author(s):

Qiang Wang ◽

Claudia Wekerle ◽

Xuezhu Wang ◽

Sergey Danilov ◽

Nikolay Koldunov ◽

...

Keyword(s):

Sea Ice ◽

Water Supply ◽

Arctic Ocean ◽

Atlantic Water ◽

Arctic Sea Ice ◽

The Arctic ◽

Fram Strait ◽

Sea Ice Decline ◽

Arctic Sea ◽

The Arctic Ocean

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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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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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