scholarly journals Impact of Synthetic Arctic Argo-Type Floats in a Coupled Ocean–Sea Ice State Estimation Framework

2020 ◽  
Vol 37 (8) ◽  
pp. 1477-1495 ◽  
Author(s):  
An T. Nguyen ◽  
Patrick Heimbach ◽  
Vikram V. Garg ◽  
Victor Ocaña ◽  
Craig Lee ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Ocean Circulation ◽  
Quantitative Methods ◽  
Numerical Models ◽  
The Arctic ◽  
Temporal Sampling ◽  
Minimum Cover ◽  
The Arctic Ocean ◽  
Western Arctic

AbstractThe lack of continuous spatial and temporal sampling of hydrographic measurements in large parts of the Arctic Ocean remains a major obstacle for quantifying mean state and variability of the Arctic Ocean circulation. This shortcoming motivates an assessment of the utility of Argo-type floats, the challenges of deploying such floats due to the presence of sea ice, and the implications of extended times of no surfacing on hydrographic inferences. Within the framework of an Arctic coupled ocean–sea ice state estimate that is constrained to available satellite and in situ observations, we establish metrics for quantifying the usefulness of such floats. The likelihood of float surfacing strongly correlates with the annual sea ice minimum cover. Within the float lifetime of 4–5 years, surfacing frequency ranges from 10–100 days in seasonally sea ice–covered regions to 1–3 years in multiyear sea ice–covered regions. The longer the float drifts under ice without surfacing, the larger the uncertainty in its position, which translates into larger uncertainties in hydrographic measurements. Below the mixed layer, especially in the western Arctic, normalized errors remain below 1, suggesting that measurements along a path whose only known positions are the beginning and end points can help constrain numerical models and reduce hydrographic uncertainties. The error assessment presented is a first step in the development of quantitative methods for guiding the design of observing networks. These results can and should be used to inform a float network design with suggested locations of float deployment and associated expected hydrographic uncertainties.

scholarly journals Recent Sea Ice Decline Did Not Significantly Increase the Total Liquid Freshwater Content of the Arctic Ocean

2018 ◽  
Vol 32 (1) ◽  
pp. 15-32 ◽  
Author(s):  
Qiang Wang ◽  
Claudia Wekerle ◽  
Sergey Danilov ◽  
Dmitry Sidorenko ◽  
Nikolay Koldunov ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Sea Ice ◽  
Arctic Ocean ◽  
Ocean Circulation ◽  
General Circulation ◽  
The Arctic ◽  
Sea Ice Decline ◽  
The Arctic Ocean ◽  
Eurasian Basin ◽  
The Impact

Abstract The freshwater stored in the Arctic Ocean is an important component of the global climate system. Currently the Arctic liquid freshwater content (FWC) has reached a record high since the beginning of the last century. In this study we use numerical simulations to investigate the impact of sea ice decline on the Arctic liquid FWC and its spatial distribution. The global unstructured-mesh ocean general circulation model Finite Element Sea Ice–Ocean Model (FESOM) with 4.5-km horizontal resolution in the Arctic region is applied. The simulations show that sea ice decline increases the FWC by freshening the ocean through sea ice meltwater and modifies upper ocean circulation at the same time. The two effects together significantly increase the freshwater stored in the Amerasian basin and reduce its amount in the Eurasian basin. The salinification of the upper Eurasian basin is mainly caused by the reduction in the proportion of Pacific Water and the increase in that of Atlantic Water (AW). Consequently, the sea ice decline did not significantly contribute to the observed rapid increase in the Arctic total liquid FWC. However, the changes in the Arctic freshwater spatial distribution indicate that the influence of sea ice decline on the ocean environment is remarkable. Sea ice decline increases the amount of Barents Sea branch AW in the upper Arctic Ocean, thus reducing its supply to the deeper Arctic layers. This study suggests that all the dynamical processes sensitive to sea ice decline should be taken into account when understanding and predicting Arctic changes.

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 Arctic Ocean circulation and variability – advection and external forcing encounter constraints and local processes

2011 ◽  
Vol 8 (6) ◽  
pp. 2313-2376 ◽  
Author(s):  
B. Rudels
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Ocean Circulation ◽  
Barents Sea ◽  
Atlantic Water ◽  
The Arctic ◽  
Fram Strait ◽  
Intermediate Layers ◽  
The Arctic Ocean ◽  
Almost All

Abstract. The first hydrographic data from the Arctic Ocean, the section from the Laptev Sea to the passage between Greenland and Svalbard obtained by Nansen on the drift by Fram 1893–1896, aptly illustrate the main features of Arctic Ocean oceanography and indicate possible processes active in transforming the water masses in the Arctic Ocean. Many, perhaps most, of these processes were identified already by Nansen, who put his mark on almost all subsequent research in the Arctic Ocean. Here we shall revisit some key questions and follow how our understanding has evolved from the early 20th century to present. What questions, if any, can now be regarded as solved and which remain still open? Five different but connected topics will be discussed: (1) The low salinity surface layer and the storage and export of freshwater. (2) The vertical heat transfer from the Atlantic water to sea ice and to the atmosphere. (3) The circulation and mixing of the two Atlantic inflow branches. (4) The formation and circulation of deep and bottom waters in the Arctic Ocean. (5) The exchanges through Fram Strait. Foci will be on the potential effects of increased freshwater input and reduced sea ice export on the freshwater storage and residence time in the Arctic Ocean, on the deep waters of the Makarov Basin and on the circulation and relative importance of the two inflows, over the Barents Sea and through Fram Strait, for the distribution of heat in the intermediate layers of the Arctic Ocean.

scholarly journals On large-scale shifts in the Arctic Ocean and sea-ice conditions during 1979−98

2001 ◽  
Vol 33 ◽  
pp. 545-550 ◽  
Author(s):  
W. Maslowski ◽  
D. C. Marble ◽  
W. Walczowski ◽  
A. J. Semtner
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Fresh Water ◽  
Ocean Circulation ◽  
Large Scale ◽  
Atlantic Water ◽  
The Arctic ◽  
Upper Ocean ◽  
Recent Climate ◽  
The Arctic Ocean

AbstractResults from a regional model of the Arctic Ocean and sea ice forced with realistic atmospheric data are analyzed to understand recent climate variability in the region. The primary simulation uses daily-averaged 1979 atmospheric fields repeated for 20 years and then continues with interannual forcing derived from the European Centre for Medium-range Weather Forecasts for 1979−98. An eastward shift in the ice-ocean circulation, fresh-water distribution and Atlantic Water extent has been determined by comparing conditions between the early 1980s and 1990s. A new trend is modeled in the late 1990s, and has a tendency to return the large-scale sea-ice and upper ocean conditions to their state in the early 1980s. Both the sea-ice and the upper ocean circulation as well as fresh-water export from the Russian shelves and Atlantic Water recirculation within the Eurasian Basin indicate that the Arctic climate is undergoing another shift. This suggests an oscillatory behavior of the Arctic Ocean system. Interannual atmospheric variability appears to be the main and sufficient driver of simulated changes. The ice cover acts as an effective dynamic medium for vorticity transfer from the atmosphere into the ocean.

Enhancement/reduction of biological pump depends on ocean circulation in the sea-ice reduction regions of the Arctic Ocean

2011 ◽  
Vol 67 (3) ◽  
pp. 305-314 ◽  
Author(s):  
Shigeto Nishino ◽  
Takashi Kikuchi ◽  
Michiyo Yamamoto-Kawai ◽  
Yusuke Kawaguchi ◽  
Toru Hirawake ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Ocean Circulation ◽  
The Arctic ◽  
Biological Pump ◽  
The Arctic Ocean ◽  
Sea Ice Reduction

scholarly journals Arctic Ocean circulation and variability – advection and external forcing encounter constraints and local processes

Ocean Science ◽  
2012 ◽  
Vol 8 (2) ◽  
pp. 261-286 ◽  
Author(s):  
B. Rudels
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Ocean Circulation ◽  
Barents Sea ◽  
Atlantic Water ◽  
The Arctic ◽  
Fram Strait ◽  
Intermediate Layers ◽  
The Arctic Ocean ◽  
Almost All

Abstract. The first hydrographic data from the Arctic Ocean, the section from the Laptev Sea to the passage between Greenland and Svalbard obtained by Nansen on his drift with Fram 1893–1896, aptly illustrate the main features of Arctic Ocean oceanography and indicate possible processes active in transforming the water masses in the Arctic Ocean. Many, perhaps most, processes were identified already by Nansen, who put his mark on almost all subsequent research in the Arctic. Here we shall revisit some key questions and follow how our understanding has evolved from the early 20th century to present. What questions, if any, can now be regarded as solved and which remain still open? Five different but connected topics will be discussed: (1) The low salinity surface layer and the storage and export of freshwater. (2) The vertical heat transfer from the Atlantic water to sea ice and to the atmosphere. (3) The circulation and mixing of the two Atlantic inflow branches. (4) The formation and circulation of deep and bottom waters in the Arctic Ocean. (5) The exchanges through Fram Strait. Foci will be on the potential effects of increased freshwater input and reduced sea ice export on the freshwater storage and residence time in the Arctic Ocean, on the deep waters of the Makarov Basin, and on the circulation and relative importance of the two inflows, over the Barents Sea and through Fram Strait, for the distribution of heat in the intermediate layers of the Arctic Ocean.

Diverting Soviet rivers: some possible repercussions for the Arctic Ocean

Polar Record ◽  
1985 ◽  
Vol 22 (140) ◽  
pp. 485-498 ◽  
Author(s):  
Howard Cattle
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Ocean Circulation ◽  
Arctic Basin ◽  
Major Effect ◽  
Water Levels ◽  
The Arctic ◽  
Current Evidence ◽  
Water Shortages ◽  
The Arctic Ocean

AbstractPlans exist in the USSR to divert southward part of the flow of some northern Russian and Siberian rivers, notably the Northern Dvina, Pechora, Ob' and Yenisey, to alleviate water shortages in Central Asia, Kazakhstan and the Ukraine, and counter falling water levels in the Aral and Caspian Seas. Possible effects of diverting small and large amounts of river water away from the Arctic are discussed in the light of recent observations and modelling studies of Arctic basin hydrology and sea ice distribution. Current evidence suggests that small diversions planned to operate before the end of this century will have little effect on ocean circulation or sea ice distribution. Larger-scale diversions planned for the future might affect sea ice formation over the shelf regions of the Kara and Barents Seas, but are unlikely to have a major effect on circulation or sea ice distribution over the Arctic Ocean as a whole.

Understanding eddy field in the Arctic Ocean from high-resolution satellite observations

2020 ◽  
Author(s):  
Igor Kozlov ◽  
Anastasia Artamonova ◽  
Larisa Petrenko ◽  
Evgeny Plotnikov ◽  
Georgy Manucharyan ◽  
...  
Keyword(s):  
High Resolution ◽  
Sea Ice ◽  
Arctic Ocean ◽  
Ocean Circulation ◽  
The Arctic ◽  
Special Focus ◽  
Deep Basin ◽  
Eddy Characteristics ◽  
Ice Concentration ◽  
The Arctic Ocean

<p>The Arctic Ocean is a host to major ocean circulation systems, many of which generate eddies that can transport water masses and corresponding tracers over long distances from their formation sites. However, comprehensive observations of critical eddy characteristics are currently not available and are limited to spatially and temporally sparse in situ observations.</p><p>Here we use multi-mission high‐resolution spaceborne synthetic aperture radar (SAR) measurements to detect eddies over open ocean and marginal ice zones (MIZ) of Fram Strait and Beaufort Gyre regions. We provide the first estimate of eddy properties, including their locations, size, vorticity sign and monthly distribution during summer period (from June to October). The results of historical Envisat ASAR observations for 2007 and 2011 are then compared to Sentinel-1 and ALOS-2 PALSAR-2 measurements acquired in 2016 and 2018, to infer the possible changes in the intensity and locations of eddy generation over the last decade.</p><p>The most prominent feature of the obtained results is that cyclonic eddies strongly dominate over anticyclones. Eddies range in size between 0.5 and 100 km and are frequently found over the shelf and near continental slopes but also present in the deep basin. For MIZ eddies, the number of eddies clearly depends on sea ice concentration with more eddies detected at the ice edge and over low ice concentration regions. The obtained results clearly show that eddies are ubiquitous in the Arctic Ocean even in the presence of sea ice and emphasize the need for improved ocean observations and modeling at eddy scales.</p><p>A special focus is also given to infer eddy dynamics over the Arctic marginal ice zones. The use of sequential Sentinel-1 SAR images enables to retrieve high-resolution velocity field over MIZ on a daily basis and observe eddy-driven MIZ dynamics down to submesoscales. The obtained eddy orbital velocities are in agreement with historical observations and may reach up to 0.5-0.7 m/s. We believe that this information is critical for better understanding of the key dynamical processes governing the MIZ state, as well as for improving and validation of sea ice and coupled ice-ocean models.</p><p>The analysis of eddies in this work was supported by RFBR grant 18‐35‐20078. Processing and analysis of Sentinel‐1 and ALOS‐2 Palsar‐2 data were done within RSF grant 18‐77‐00082. Software development for data analysis in this work was made under the Ministry of Science and Higher Education of the Russian Federation contract 0555‐2019‐0001.</p>

scholarly journals Ice-Tethered Profiler Measurements of Dissolved Oxygen under Permanent Ice Cover in the Arctic Ocean

2010 ◽  
Vol 27 (11) ◽  
pp. 1936-1949 ◽  
Author(s):  
M.-L. Timmermans ◽  
R. Krishfield ◽  
S. Laney ◽  
J. Toole
Keyword(s):  
Sea Ice ◽  
Dissolved Oxygen ◽  
Arctic Ocean ◽  
Water Column ◽  
Ocean Circulation ◽  
Oxygen Sensor ◽  
Ice Cover ◽  
The Arctic ◽  
Surface Mixed Layer ◽  
The Arctic Ocean

Abstract Four ice-tethered profilers (ITPs), deployed between 2006 and 2009, have provided year-round dissolved oxygen (DO) measurements from the surface mixed layer to 760-m depth under the permanent sea ice cover in the Arctic Ocean. These ITPs drifted with the permanent ice pack and returned 2 one-way profiles per day of temperature, salinity, and DO. Long-term calibration drift of the oxygen sensor can be characterized and removed by referencing to recently calibrated ship DO observations on deep isotherms. Observed changes in the water column time series are due to both drift of the ITP into different water masses and seasonal variability, driven by both physical and biological processes within the water column. Several scientific examples are highlighted that demonstrate the considerable potential for sustained ITP-based DO measurements to better understand the Arctic Ocean circulation patterns and biogeochemical processes beneath the sea ice.

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