scholarly journals Arctic Ocean outflow and glacier–ocean interaction modify water over the Wandel Sea shelf, northeast Greenland

2017 ◽  
Author(s):  
Igor A. Dmitrenko ◽  
Sergei A. Kirillov ◽  
Bert Rudels ◽  
David G. Babb ◽  
Leif Toudal Pedersen ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Continental Slope ◽  
The Arctic ◽  
Fram Strait ◽  
Ambient Water ◽  
Pacific Water ◽  
The Pacific ◽  
The Arctic Ocean ◽  
Water Outflow ◽  
Polar Water

Abstract. The first-ever conductivity–temperature–depth (CTD) observations on the Wandel Sea shelf in North Eastern Greenland were collected in April–May 2015. They were complemented by CTD profiles taken along the continental slope during the Norwegian FRAM 2014–15 drift. The CTD profiles are used to reveal the origin of water masses and interactions with ambient water from the continental slope and the outlet glaciers. The subsurface water is associated with the Pacific Water outflow from the Arctic Ocean. The underlying Halocline separates the Pacific Water from a deeper layer of Polar Water that has interacted with the warm Atlantic water outflow through Fram Strait recorded below 140 m. Over the outer shelf, the Halocline shows numerous cold density-compensated intrusions indicating lateral interaction with an ambient Polar Water mass across the continental slope. At the glacier front, colder and turbid water intrusions were observed at the base of the Halocline. In temperature–salinity space, these data follow a mixing line that diverges from ambient water properties and indicates ocean–glacier interaction. Our observations of Pacific Water are set within the context of upstream observations in the Beaufort Sea and downstream observations from the Northeast Water Polynya and clearly show the modification of Pacific water during its advection across the Arctic Ocean. Moreover, ambient water over the Wandel Sea slope shows different thermohaline structures indicating the different origin and pathways of the on-shore and off-shore branches of the Arctic Ocean outflow through western Fram Strait.

scholarly journals Arctic Ocean outflow and glacier–ocean interactions modify water over the Wandel Sea shelf (northeastern Greenland)

Ocean Science ◽  
2017 ◽  
Vol 13 (6) ◽  
pp. 1045-1060 ◽  
Author(s):  
Igor A. Dmitrenko ◽  
Sergey A. Kirillov ◽  
Bert Rudels ◽  
David G. Babb ◽  
Leif Toudal Pedersen ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Continental Slope ◽  
The Arctic ◽  
Ambient Water ◽  
Pacific Water ◽  
The Pacific ◽  
Tidewater Glacier ◽  
The Arctic Ocean ◽  
Water Outflow ◽  
Polar Water

Abstract. The first-ever conductivity–temperature–depth (CTD) observations on the Wandel Sea shelf in northeastern Greenland were collected in April–May 2015. They were complemented by CTDs taken along the continental slope during the Norwegian FRAM 2014–2015 drift. The CTD profiles are used to reveal the origin of water masses and interactions with ambient water from the continental slope and the tidewater glacier outlet. The subsurface water is associated with the Pacific water outflow from the Arctic Ocean. The underlying halocline separates the Pacific water from a deeper layer of polar water that has interacted with the warm Atlantic water outflow through the Fram Strait, recorded below 140 m. Over the outer shelf, the halocline shows numerous cold density-compensated intrusions indicating lateral interaction with an ambient polar water mass across the continental slope. At the front of the tidewater glacier outlet, colder and turbid water intrusions were observed at the base of the halocline. On the temperature–salinity plots these stations indicate a mixing line that is different from the ambient water and seems to be conditioned by the ocean–glacier interaction. Our observations of Pacific water are set within the context of upstream observations in the Beaufort Sea and downstream observations from the Northeast Water Polynya, and clearly show the modification of Pacific water during its advection across the Arctic Ocean. Moreover, ambient water over the Wandel Sea slope shows different thermohaline structures indicating the different origin and pathways of the on-shore and off-shore branches of the Arctic Ocean outflow through the western Fram Strait.

scholarly journals Export of Arctic freshwater components through the Fram Strait 1998–2010

2012 ◽  
Vol 9 (4) ◽  
pp. 2749-2792
Author(s):  
B. Rabe ◽  
P. Dodd ◽  
E. Hansen ◽  
E. Falck ◽  
U. Schauer ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
The Arctic ◽  
Ice Formation ◽  
Fram Strait ◽  
Pacific Water ◽  
Ice Melt ◽  
The North ◽  
Beaufort Gyre ◽  
The Pacific ◽  
The Arctic Ocean

Abstract. The East Greenland Current in the Western Fram Strait is an important pathway for liquid freshwater export from the Arctic Ocean to the Nordic Seas and the North Atlantic subpolar gyre. We analysed five hydrographic surveys and data from moored current meters around 79° N in the Western Fram Strait between 1998 and 2010. To estimate the composition of southward liquid freshwater transports, inventories of liquid freshwater and components from Dodd et al. (2012) were combined with transport estimates from an inverse model between 10.6° W and 4° E. The southward liquid freshwater transports through the section averaged to 92 mSv (2900 km3 yr−1), relative to a salinity of 34.9. The transports consisted of 123 mSv water from rivers and precipitation (meteoric water), 28 mSv freshwater from the Pacific and 60 mSv freshwater deficit due to brine from ice formation. Variability in liquid freshwater and component transports appear to have been partly due to advection of these water masses to the Fram Strait and partly due to variations in the local volume transport; an exception are Pacific Water transports, which showed little co-variability with volume transports. An increase in Pacific Water transports from 2005 to 2010 suggests a release of Pacific Water from the Beaufort Gyre, in line with an observed expansion of Pacific Water towards the Eurasian Basin. The co-variability of meteoric water and brine from ice formation suggests joint processes in the main sea ice formation regions on the Arctic Ocean shelves. In addition, enhanced levels of sea ice melt observed in 2009 likely led to reduced transports of brine from ice formation. At least part of this additional ice melt appears to have been advected from the Beaufort Gyre and from north of the Bering Strait towards the Fram Strait. The observed changes in liquid freshwater component transports are much larger than known trends in the Arctic liquid freshwater inflow from rivers and the Pacific. Instead, recent observations of an increased storage of liquid freshwater in the Arctic Ocean suggest a decreased export of liquid freshwater. This raises the question how fast the accumulated liquid freshwater will be exported from the Arctic Ocean to the deep water formation regions in the North Atlantic and if an increased export will occur through the Fram Strait.

scholarly journals Wind-forced depth-dependent currents over the eastern Beaufort Sea continental slope: Implications for Pacific water transport

Elem Sci Anth ◽  
2018 ◽  
Vol 6 ◽  
Author(s):  
Igor A. Dmitrenko ◽  
Sergei A. Kirillov ◽  
Paul G. Myers ◽  
Alexandre Forest ◽  
Bruno Tremblay ◽  
...  
Keyword(s):  
Pressure Gradient ◽  
Arctic Ocean ◽  
Continental Slope ◽  
Water Transport ◽  
Beaufort Sea ◽  
The Arctic ◽  
Pacific Water ◽  
Barotropic Flow ◽  
The Pacific ◽  
The Arctic Ocean

Pacific water contributes significantly to the Arctic Ocean freshwater budget. Recent increases in Arctic freshwater flux, also affected by the Pacific-derived Arctic water, impact the Atlantic overturning circulation with implications for global climate. The interannual variability of the Pacific water outflow remains poorly understood, partly due to different branches of the Pacific water flow in the Arctic Ocean. The shelfbreak current over the Beaufort Sea continental slope transports ~50% of the Pacific-derived water eastward along the Beaufort Sea continental slope towards the Canadian Archipelago. The oceanographic mooring deployed over the eastern Beaufort Sea continental slope in October 2003 recorded current velocities through depths of 28–108 m until September 2005. Data analysis revealed that these highly energetic currents have two different modes of depth-dependent behaviour. The downwelling-favourable wind associated with cyclones passing north of the Beaufort Sea continental slope toward the Canadian Archipelago generates depth-intensified shelfbreak currents with along-slope northeastward flow. A surface Ekman on-shore transport and associated increase of the sea surface heights over the shelf produce a cross-slope pressure gradient that drives an along-slope northeastward barotropic flow, in the same direction as the wind. In contrast, the upwelling-favourable wind associated with deep Aleutian Low cyclones over the Alaskan Peninsula and/or Aleutian Island Arc leads to surface-intensified currents with along-slope westward flow. This northeasterly wind generates a surface Ekman transport that moves surface waters offshore. The associated cross-slope pressure gradient drives an along-slope southwestward barotropic flow. The wind-driven barotropic flow generated by upwelling and downwelling is superimposed on the background bottom-intensified shelfbreak current. For downwelling, this flow amplifies the depth-intensified background baroclinic circulation with enhanced Pacific water transport towards the Canadian Archipelago. For upwelling, the shelfbreak current is reversed, which results in surface-intensified flow in the opposite direction. These results are supported by numerical simulations.

scholarly journals Structure and dynamics of mesoscale eddies over the Laptev Sea continental slope in the Arctic Ocean

2018 ◽  
Author(s):  
Andrey Pnyushkov ◽  
Igor V. Polyakov ◽  
Laurie Padman ◽  
An T. Nguyen
Keyword(s):  
Arctic Ocean ◽  
Continental Slope ◽  
Mesoscale Eddies ◽  
The Arctic ◽  
Laptev Sea ◽  
Surface Mixed Layer ◽  
Fram Strait ◽  
Structure And Dynamics ◽  
The Arctic Ocean ◽  
The Laptev Sea

Abstract. Heat fluxes steered by mesoscale eddies may be a significant (but still not quantified) source of heat to the surface mixed layer and sea ice cover in the Arctic Ocean, as well as a source of nutrients for enhancing seasonal productivity in the near-surface layers. Here we use four years (2007–2011) of velocity and hydrography records from a moored profiler over the Laptev Sea slope, and 15 months (2008–2009) of acoustic Doppler current profiler data from a nearby mooring, to investigate the structure and dynamics of eddies at the continental margin of the eastern Eurasian Basin. Typical eddy scales are radii of order of 10 km, heights of six hundred meters, and maximum velocities of ~ 0.1 m s −1. Eddies are approximately equally divided between cyclonic and anticyclonic polarizations, contrary to prior observations from the deep basins and along the Lomonosov Ridge. Eddies are present in the mooring records about 20–25 % of the time, taking about one week to pass through the mooring at an average frequency of about one eddy per month. We found the eddies observed are formed in two distinct regions–near Fram Strait, where the western branch of Atlantic Water (AW) enters the Arctic Ocean, and near Severnaya Zemlya, where the Fram Strait and Barents Sea branches of the AW inflow merge. These eddies, embedded in the Arctic Circumpolar Boundary Current, carry anomalous water properties along the eastern Arctic continental slope. The enhanced diapycnal mixing that we found within EB eddies suggests a potentially important role for eddies in the vertical redistribution of heat in the Arctic Ocean interior.

scholarly journals Hotspots of Dense Water Cascading in the Arctic Ocean: Implications for the Pacific Water Pathways

2020 ◽  
Vol 125 (10) ◽  
Author(s):  
Maria V. Luneva ◽  
Vladimir V. Ivanov ◽  
Fedor Tuzov ◽  
Yevgeny Aksenov ◽  
James D. Harle ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
The Arctic ◽  
Pacific Water ◽  
Dense Water ◽  
The Pacific ◽  
The Arctic Ocean

Pacific Water Pathways through the Arctic Ocean

2020 ◽  
Author(s):  
Paul A. Dodd ◽  
Tore Hattermann ◽  
Michael Karcher ◽  
Frank Kauker ◽  
Colin Stedmon
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Large Scale ◽  
The Arctic ◽  
Fram Strait ◽  
Bering Strait ◽  
Wind Fields ◽  
Pacific Water ◽  
Back Trajectories ◽  
The Arctic Ocean

<p>The volume, characteristics and sources of freshwater circulating in the Arctic Ocean vary in time and are expected to change under a declining sea ice cover, influencing the physical environment and Arctic ecosystem. Relatively fresh (S = 32) Pacific Water, which enters the Arctic Ocean via the Bering Strait makes up a significant part of the liquid freshwater exiting the Arctic Ocean through Fram Strait. If transported to the Nordic Seas and North Atlantic via the East- and West Greenland Currents freshwater from the Pacific could have an effect on convection and dense water formation in those regions.</p><p>More than 30 repeated sections of nutrient measurements have been collected across Fram Strait between 1980 and 2019. The fraction of Pacific Water along these repeated sections can be estimated from the ratio of nitrate to phosphate. The time-series of repeated Fram Strait sections indicates that the fraction of Pacific Water passing out of the Arctic Ocean has changed significantly over the last 30 years. Pacific water fractions remained high from 1980 to 1998, but in 1999 Pacific water almost disappeared from Fram Strait, reappearing from 2011 to 2012, when there was a peak in freshwater export though Fram Strait.</p><p>Several hypotheses suggest how variations in the large-scale atmospheric circulation over the Arctic Ocean may influence the transport and pathways of Pacific Water. We show how anomalies in reanalysis wind fields are associated with the reappearance of Pacific Water in Fram Strait in recent years. Repeated sections across Fram Strait are compared with sea ice back-trajectories in the Polar Pathfinder 4 product and a simulated Pacific Water tracer in the NAOSIM numerical model to investigate likely Pacific water pathways through the Arctic Ocean and upstream drivers of changes observed in Fram Strait.</p>

scholarly journals Liquid export of Arctic freshwater components through the Fram Strait 1998–2011

Ocean Science ◽  
2013 ◽  
Vol 9 (1) ◽  
pp. 91-109 ◽  
Author(s):  
B. Rabe ◽  
P. A. Dodd ◽  
E. Hansen ◽  
E. Falck ◽  
U. Schauer ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Meteoric Water ◽  
The Arctic ◽  
Ice Formation ◽  
Fram Strait ◽  
Pacific Water ◽  
Ice Melt ◽  
The North ◽  
The Arctic Ocean

Abstract. We estimated the magnitude and composition of southward liquid freshwater transports in the East Greenland Current near 79° N in the Western Fram Strait between 1998 and 2011. Previous studies have found this region to be an important pathway for liquid freshwater export from the Arctic Ocean to the Nordic Seas and the North Atlantic subpolar gyre. Our transport estimates are based on six hydrographic surveys between June and September and concurrent data from moored current meters. We combined concentrations of liquid freshwater, meteoric water (river water and precipitation), sea ice melt and brine from sea ice formation, and Pacific Water, presented in Dodd et al. (2012), with volume transport estimates from an inverse model. The average of the monthly snapshots of southward liquid freshwater transports between 10.6° W and 4° E is 100 ± 23 mSv (3160 ± 730 km3 yr−1), relative to a salinity of 34.9. This liquid freshwater transport consists of about 130% water from rivers and precipitation (meteoric water), 30% freshwater from the Pacific, and −60% (freshwater deficit) due to a mixture of sea ice melt and brine from sea ice formation. Pacific Water transports showed the highest variation in time, effectively vanishing in some of the surveys. Comparison of our results to the literature indicates that this was due to atmospherically driven variability in the advection of Pacific Water along different pathways through the Arctic Ocean. Variations in most liquid freshwater component transports appear to have been most strongly influenced by changes in the advection of these water masses to the Fram Strait. However, the local dynamics represented by the volume transports influenced the liquid freshwater component transports in individual years, in particular those of sea ice melt and brine from sea ice formation. Our results show a similar ratio of the transports of meteoric water and net sea ice melt as previous studies. However, we observed a significant increase in this ratio between the surveys in 1998 and in 2009. This can be attributed to higher concentrations of sea ice melt in 2009 that may have been due to enhanced advection of freshwater from the Beaufort Gyre to the Fram Strait. Known trends and variability in the Arctic liquid freshwater inflow from rivers are not likely to have had a significant influence on the variation of liquid freshwater component transports between our surveys. On the other hand, known freshwater inflow variability from the Pacific could have caused some of the variation we observed in the Fram Strait. The apparent absence of a trend in southward liquid freshwater transports through the Fram Strait and recent evidence of an increase in liquid freshwater storage in the Arctic Ocean raise the question: how fast will the accumulated liquid freshwater be exported from the Arctic Ocean to the deep water formation regions in the North Atlantic and will an increased export occur through the Fram Strait.

scholarly journals Structure and dynamics of mesoscale eddies over the Laptev Sea continental slope in the Arctic Ocean

Ocean Science ◽  
2018 ◽  
Vol 14 (5) ◽  
pp. 1329-1347 ◽  
Author(s):  
Andrey Pnyushkov ◽  
Igor V. Polyakov ◽  
Laurie Padman ◽  
An T. Nguyen
Keyword(s):  
Arctic Ocean ◽  
Continental Slope ◽  
Mesoscale Eddies ◽  
The Arctic ◽  
Laptev Sea ◽  
Surface Mixed Layer ◽  
Fram Strait ◽  
Structure And Dynamics ◽  
The Arctic Ocean ◽  
The Laptev Sea

Abstract. Heat fluxes steered by mesoscale eddies may be a significant, but still not quantified, source of heat to the surface mixed layer and sea ice cover in the Arctic Ocean, as well as a source of nutrients for enhancing seasonal productivity in the near-surface layers. Here we use 4 years (2007–2011) of velocity and hydrography records from a moored profiler over the Laptev Sea slope and 15 months (2008–2009) of acoustic Doppler current profiler data from a nearby mooring to investigate the structure and dynamics of eddies at the continental margin of the eastern Eurasian Basin. Typical eddy scales are radii of the order of 10 km, heights of 600 m, and maximum velocities of ∼0.1 m s−1. Eddies are approximately equally divided between cyclonic and anticyclonic polarizations, contrary to prior observations from the deep basins and along the Lomonosov Ridge. Eddies are present in the mooring records about 20 %–25 % of the time, taking about 1 week to pass through the mooring at an average frequency of about one eddy per month. We found that the eddies observed are formed in two distinct regions – near Fram Strait, where the western branch of Atlantic Water (AW) enters the Arctic Ocean, and near Severnaya Zemlya, where the Fram Strait and Barents Sea branches of the AW inflow merge. These eddies, embedded in the Arctic Circumpolar Boundary Current, carry anomalous water properties along the eastern Arctic continental slope. The enhanced diapycnal mixing that we found within EB eddies suggests a potentially important role for eddies in the vertical redistribution of heat in the Arctic Ocean interior.

scholarly journals Seasonal patterns in Arctic planktonic metabolism (Fram Strait – Svalbard region)

2013 ◽  
Vol 10 (3) ◽  
pp. 1451-1469 ◽  
Author(s):  
R. Vaquer-Sunyer ◽  
C. M. Duarte ◽  
J. Holding ◽  
A. Regaudie-de-Gioux ◽  
L. S. García-Corral ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Early Spring ◽  
The Arctic ◽  
Fram Strait ◽  
Metabolic Rates ◽  
Net Community Production ◽  
Western Sector ◽  
The Arctic Ocean ◽  
European Arctic ◽  
Community Production

Abstract. The metabolism of the Arctic Ocean is marked by extremely pronounced seasonality and spatial heterogeneity associated with light conditions, ice cover, water masses and nutrient availability. Here we report the marine planktonic metabolic rates (net community production, gross primary production and community respiration) along three different seasons of the year, for a total of eight cruises along the western sector of the European Arctic (Fram Strait – Svalbard region) in the Arctic Ocean margin: one at the end of 2006 (fall/winter), two in 2007 (early spring and summer), two in 2008 (early spring and summer), one in 2009 (late spring–early summer), one in 2010 (spring) and one in 2011 (spring). The results show that the metabolism of the western sector of the European Arctic varies throughout the year, depending mostly on the stage of bloom and water temperature. Here we report metabolic rates for the different periods, including the spring bloom, summer and the dark period, increasing considerably the empirical basis of metabolic rates in the Arctic Ocean, and especially in the European Arctic corridor. Additionally, a rough annual metabolic estimate for this area of the Arctic Ocean was calculated, resulting in a net community production of 108 g C m−2 yr−1.

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