scholarly journals Mooring-Based Observations of Double-Diffusive Staircases over the Laptev Sea Slope*

2012 ◽  
Vol 42 (1) ◽  
pp. 95-109 ◽  
Author(s):  
Igor V. Polyakov ◽  
Andrey V. Pnyushkov ◽  
Robert Rember ◽  
Vladimir V. Ivanov ◽  
Y.-D. Lenn ◽  
...  
Keyword(s):  
Double Diffusion ◽  
Atlantic Water ◽  
Arctic Sea Ice ◽  
Heat Fluxes ◽  
Laptev Sea ◽  
Depth Range ◽  
Diffusive Convection ◽  
Arctic Sea ◽  
Effective Transfer ◽  
The Laptev Sea

Abstract A yearlong time series from mooring-based high-resolution profiles of water temperature and salinity from the Laptev Sea slope (2003–04; 2686-m depth; 78°26′N, 125°37′E) shows six remarkably persistent staircase layers in the depth range of ~140–350 m encompassing the upper Atlantic Water (AW) and lower halocline. Despite frequent displacement of isopycnal surfaces by internal waves and eddies and two strong AW warming pulses that passed through the mooring location in February and late August 2004, the layers preserved their properties. Using laboratory-derived flux laws for diffusive convection, the authors estimate the time-averaged diapycnal heat fluxes across the four shallower layers overlying the AW core to be ~8 W m−2. Temporal variability of these fluxes is strong, with standard deviations of ~3–7 W m−2. These fluxes provide a means for effective transfer of AW heat upward over more than a 100-m depth range toward the upper halocline. These findings suggest that double diffusion is an important mechanism influencing the oceanic heat fluxes that help determine the state of Arctic sea ice.

scholarly journals Spatial and Temporal Variations in the Extent and Thickness of Arctic Landfast Ice

2019 ◽  
Vol 12 (1) ◽  
pp. 64 ◽  
Author(s):  
Zixuan Li ◽  
Jiechen Zhao ◽  
Jie Su ◽  
Chunhua Li ◽  
Bin Cheng ◽  
...  
Keyword(s):  
Sea Ice ◽  
Coastal Areas ◽  
Arctic Sea Ice ◽  
Ice Thickness ◽  
Laptev Sea ◽  
Maximum Extent ◽  
Arctic Sea ◽  
Landfast Ice ◽  
The Mean ◽  
The Laptev Sea

Analyses of landfast ice in Arctic coastal areas provide a comprehensive understanding of the variations in Arctic sea ice and generate data for studies on the utilization of the Arctic passages. Based on our analysis, Arctic landfast ice mainly appears in January–June and is distributed within the narrow straits of the Canadian Archipelago (nearly 40%), the coastal areas of the East Siberian Sea, the Laptev Sea, and the Kara Sea. From 1976–2018, the landfast ice extent gradually decreased at an average rate of −1.1 ± 0.5 × 104 km2/yr (10.5% per decade), while the rate of decrease for entire Arctic sea ice was −6.0 ± 2.4 × 104 km2/yr (5.2% per decade). The annual maximum extent reached 2.3 × 106 km2 in the early 1980s, and by 2018, the maximum extent decreased by 0.6 × 106 km2, which is an area approximately equivalent the Laptev Sea. The mean duration of Arctic landfast ice is 44 weeks, which has gradually been reduced at a rate of −0.06 ± 0.03 weeks/yr. Regional landfast ice extent decreases in 16 of the 17 subregions except for the Bering Sea, making it the only subregion where both the extent and duration increases. The maximum mean landfast ice thickness appears in the northern Canadian Archipelago (>2.5 m), with the highest increasing trend (0.1 m/yr). In the Northeast Passage, the mean landfast ice thickness is 1.57 m, with a slight decreasing trend of −1.2 cm/yr, which is smaller than that for entire Arctic sea ice (−5.1 cm/yr). The smaller decreasing trend in the landfast ice extent and thickness suggests that the well-known Arctic sea ice decline largely occurred in the pack ice zone, while the larger relative extent loss indicates a faster ice free future in the landfast ice zone.

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

2020 ◽  
Vol 47 (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

Air-Sea Fluxes following the Unusually Early Ice Retreats in the Arctic

2020 ◽  
Author(s):  
Dongxiao Zhang ◽  
Chidong Zhang ◽  
Jessica Cross ◽  
Calvin Mordy ◽  
Edward Cokelet ◽  
...  
Keyword(s):  
Sea Ice ◽  
Numerical Models ◽  
Green Energy ◽  
Arctic Sea Ice ◽  
Heat Fluxes ◽  
The Arctic ◽  
Energy Fluxes ◽  
The Pacific ◽  
Arctic Sea ◽  
Ice Retreat

<p>The Arctic has been rapidly changing over the last decade, with more frequent unusually early ice retreats in late spring and summer. Vast Arctic areas that were usually covered by sea ice are now exposed to the atmosphere because of earlier ice retreat and later arrival. Assessment of consequential changes in the energy cycle of the Arctic and their potential feedback to the variability of Arctic sea ice and marine ecosystems critically depends on the accuracy of surface flux estimates. In the Pacific sector of the Arctic, earlier ice retreat generally follows the warm Pacific water inflow into the Arctic through the Bering and Chukchi Seas. Due to ice coverage and irregularity of seasonal ice retreats, air-sea flux measurements following the ice retreats has been difficult to plan and execute. A recent technology development is the Unmanned Surface Vehicles (USVs): The long-range USV saildrones are powered by green energy with wind for propulsion and solar energy for instrumentation and vehicle control. NOAA/PMEL and University of Washington scientists have made surface measurements of the ocean and atmosphere in the Pacific Arctic using saildrones for the past several years. In 2019, for the 1<sup>st</sup> time a fleet of six saildrones capable of measuring both turbulent and radiative heat fluxes, wind stress, air-sea CO<sub>2</sub> flux and upper ocean currents was deployed to follow the ice retreat from May to October, with five of the USVs into the Chukchi and Beaufort Seas while one staying in the Bering Sea. These in situ measurements provide rare opportunities of estimating air-sea energy fluxes during a period of rapid reduction in Arctic sea ice in different scenarios: open water after ice melt, free-floating ice bands, and marginal ice zones. In this study, Arctic air-sea heat and momentum fluxes measured by the saildrones are compared to gridded flux products based on satellite data and numerical models to investigate the circumstances under which they agree and differ, and the main sources of their discrepancies. The results will quantify the uncertainty margins in the gridded flux products and provide insights needed to improve their accuracy. We will also discuss the feasibility of using USVs in sustained Arctic observing system to collect benchmark datasets of the changing surface energy fluxes due to rapid sea ice reduction and provide real time data for improved weather and ocean forecasts.  </p>

scholarly journals North Atlantic warming and declining volume of arctic sea ice

2013 ◽  
Vol 7 (1) ◽  
pp. 245-265 ◽  
Author(s):  
V. A. Alexeev ◽  
V. V. Ivanov ◽  
R. Kwok ◽  
L. H. Smedsrud
Keyword(s):  
Sea Ice ◽  
Large Scale ◽  
Atlantic Water ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Ice Thickness ◽  
First Year ◽  
Pacific Water ◽  
Svalbard Archipelago ◽  
Arctic Sea

Abstract. Long-term thinning of arctic sea ice over the last few decades has resulted in significant declines in the coverage of thick multi-year ice accompanied by a proportional increase in thinner first-year ice. This change is often attributed to changes in the arctic atmosphere, both in composition and large-scale circulation, and greater inflow of warmer Pacific water through the Bering Strait. The Atlantic Water (AW) entering the Arctic through Fram Strait has often been considered less important because of strong stratification in the Arctic Ocean and the deeper location of AW compared to Pacific water. In our combined examination of oceanographic measurements and satellite observations of ice concentration and thickness, we find evidence that AW has a direct impact on the thinning of arctic sea ice downstream of Svalbard Archipelago. The affected area extends as far as Severnaya Zemlya Archipelago. The imprints of AW appear as local minima in sea ice thickness; ice thickness is significantly less than that expected of first-year ice. Our lower-end conservative estimates indicate that the recent AW warming episode could have contributed up to 150–200 km3 of sea ice melt per year, which would constitute about 20% of the total 900 km3yr−1 negative trend in sea ice volume since 2004.

Comparison of MODIS-based thin-ice thicknesses with ice draft measurements in the Laptev Sea & Chukchi Sea

2021 ◽  
Author(s):  
Andreas Preußer ◽  
H. Jakob Belter ◽  
Yasushi Fukamachi ◽  
Günther Heinemann
Keyword(s):  
Sea Ice ◽  
Chukchi Sea ◽  
Reanalysis Data ◽  
Arctic Sea Ice ◽  
Balance Model ◽  
Ice Thickness ◽  
Laptev Sea ◽  
Data Set ◽  
In Situ Data ◽  
The Laptev Sea

<p>Acquiring information about the thickness of thin Arctic sea-ice is an important aspect of assessing atmosphere – sea-ice – ocean interactions, as the ice thickness directly relates to the magnitude of energy fluxes at the sea-ice interfaces. In winter, these fluxes are linked to sea-ice formation and hence accompanying processes such as physically induced upper-ocean convection and turbulent mixing of the lower atmospheric boundary layer. It remains a big challenge to validate satellite-derived thin-ice thicknesses, first and foremost due to the lack of suitable in-situ data in these remote areas.</p><p>In order to address this issue, we here present the first insight into a comparison between high-resolution (2km) MODIS thermal infrared satellite data (available for 2002/2003 to 2017/2018) and comprehensive time series of ice-draft data obtained from moored Ice Profiling Sonar (IPS) data. The IPS data set comprises winter-seasons 2009/2010 to 2011/2012 in the Chukchi Sea and winter-seasons 2013/2014 to 2014/2015 in the Laptev Sea. For the MODIS data set, a 1D energy balance model serves as the base for deriving thin-ice thicknesses (0 to 50 cm) from ice-surface temperature swath-data and ERA-Interim atmospheric reanalysis data. In order to facilitate the comparison, the 1Hz IPS ice-draft data is first empirically converted to ice thickness and afterwards resampled to 5-minute modal-values to find matching MODIS swath data.</p><p>It shows that the agreement between the MODIS and IPS ice-thickness data largely depends on the thickness of the ice sampled by the IPS. We found the highest agreement for ice thickness values below 20 cm, which tend to appear more frequently at the Chukchi Sea mooring location. More generally, we notice that MODIS seems to overestimate ice thicknesses up to approximately 40 cm. For thicker ice, the limitations of the MODIS ice-thickness retrieval result in an underestimation.</p>

scholarly journals Impact of increasing inflow of warm Atlantic water on the sea‐air exchange of carbon dioxide and methane in the Laptev Sea

2016 ◽  
Vol 121 (7) ◽  
pp. 1867-1883
Author(s):  
Iréne Wåhlström ◽  
Christian Dieterich ◽  
Per Pemberton ◽  
H. E. Markus Meier
Keyword(s):  
Carbon Dioxide ◽  
Atlantic Water ◽  
Laptev Sea ◽  
The Laptev Sea ◽  
Air Exchange

scholarly journals Winter sea ice export from the Laptev Sea preconditions the local summer sea ice cover and fast ice decay

2017 ◽  
Vol 11 (5) ◽  
pp. 2383-2391 ◽  
Author(s):  
Polona Itkin ◽  
Thomas Krumpen
Keyword(s):  
Sea Ice ◽  
Numerical Models ◽  
Ice Cover ◽  
Sensitivity Study ◽  
Arctic Sea Ice ◽  
Late Winter ◽  
Laptev Sea ◽  
Ice Dynamics ◽  
Fast Ice ◽  
The Laptev Sea

Abstract. Ice retreat in the eastern Eurasian Arctic is a consequence of atmospheric and oceanic processes and regional feedback mechanisms acting on the ice cover, both in winter and summer. A correct representation of these processes in numerical models is important, since it will improve predictions of sea ice anomalies along the Northeast Passage and beyond. In this study, we highlight the importance of winter ice dynamics for local summer sea ice anomalies in thickness, volume and extent. By means of airborne sea ice thickness surveys made over pack ice areas in the south-eastern Laptev Sea, we show that years of offshore-directed sea ice transport have a thinning effect on the late-winter sea ice cover. To confirm the preconditioning effect of enhanced offshore advection in late winter on the summer sea ice cover, we perform a sensitivity study using a numerical model. Results verify that the preconditioning effect plays a bigger role for the regional ice extent. Furthermore, they indicate an increase in volume export from the Laptev Sea as a consequence of enhanced offshore advection, which has far-reaching consequences for the entire Arctic sea ice mass balance. Moreover we show that ice dynamics in winter not only preconditions local summer ice extent, but also accelerate fast-ice decay.

scholarly journals Modified Halocline Water over the Laptev Sea Continental Margin: Historical Data Analysis

2012 ◽  
Vol 25 (16) ◽  
pp. 5556-5565 ◽  
Author(s):  
Igor A. Dmitrenko ◽  
Sergey A. Kirillov ◽  
Vladimir V. Ivanov ◽  
Bert Rudels ◽  
Nuno Serra ◽  
...  
Keyword(s):  
Continental Margin ◽  
North Atlantic Ocean ◽  
Source Region ◽  
Vertical Mixing ◽  
Atlantic Water ◽  
Laptev Sea ◽  
Boundary Current ◽  
Salinity Stratification ◽  
The North ◽  
The Laptev Sea

Abstract Historical hydrographic data (1940s–2010) show a distinct cross-slope difference of the lower halocline water (LHW) over the Laptev Sea continental margins. Over the slope, the LHW is on average warmer and saltier by 0.2°C and 0.5 psu, respectively, relative to the off-slope LHW. The LHW temperature time series constructed from the on-slope historical records are related to the temperature of the Atlantic Water (AW) boundary current transporting warm water from the North Atlantic Ocean. In contrast, the on-slope LHW salinity is linked to the sea ice and wind forcing over the potential upstream source region in the Barents and northern Kara Seas, as also indicated by hydrodynamic model results. Over the Laptev Sea continental margin, saltier LHW favors weaker salinity stratification that, in turn, contributes to enhanced vertical mixing with underlying AW.

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