Our favorite satellite archives are experiencing data glitches. This may be at the server level rather than at the satellite source. This could be related to weekend lack of staffing, covid19, elections, departure of staff, policy change and so on.
[[Update: most of the missing files have been posted as of 22:37 UTC Monday 09 Nov 2020.]]
The most serious of these has been SMOS ice thinness since it is used in mulltiple products, notably Cryo2SMOS and SMOS-SMAP. However it has recovered and is gapless over the freeze season. The glitches in other products are unlikely to ever be repaired so for our time series so we will be 'walking in' from the boundaries with duplicated data since it is not possible to interpolate without netCDF grayscales.
SMOS-SMAP is an improved version of SMOS and is served with a respectable enlargement. However given the complex palette it is difficult to make an autumn comparison of the two. After the last of the open water in the Laptev disappears over the next few days (?), the next thing to do is follow the creep of >0.5m thickness which helps measure the delay in the 2020 freeze season.
The very thin regions of ice are too dark in the original palette but can be replaced fairly well via a color-picker. These special peripheral regions will remain of interest into January for the Bering Strait and Sv-FJL-SZ area.
The SSTfnd 10m water column temperature may still be several degrees from the -1.8ºC below the newly forming ice. This product successfully predicted the last regions of the Laptev to stay open via its earlier hotspots.
Oren and FooW have brought up the issue of buoyant fresh river water draining into the Arctic Ocean to form a stratified surface layer with a more easily attained freezing point, eg 0ºC. (Because newly forming ice extrudes brine, when that ice melts, it too provides an extensive freshwater layer.)
That's complicated for the Lena whose delta lies south of the NSI island barrier but fortunately a Sept 2020 paper and three recent others address this very subject. The Lena is the largest Arctic riverine source and still has a substantial in-flow up to November. The authors provide a very detailed history of average freeze-up and melt-out dates that can be the basis for a 2020 anomaly map here.
"On the Variability of Stratification in the Freshwater-Influenced Laptev Sea Region
M Janout et al 15 Sep 2020 free full text
https://www.frontiersin.org/articles/10.3389/fmars.2020.543489/fullWe investigate seasonal and spatial variability of stratification on the Siberian shelves with a case study from the Laptev Sea based on shipboard hydrographic measurements, year-round oceanographic mooring records from 2013 to 2014 and chemical tracer-based water mass analyses. In summer 2013, weak onshore-directed winds caused spreading of riverine waters throughout much of the eastern and central shelf.
In contrast, strong southerly winds in summer 2014 diverted much of the freshwater to the northeast, which resulted in 50% less river water and significantly weaker stratification on the central shelf compared with the previous year. Our year-long records additionally emphasize the regional differences in water column structure and stratification, where the northwest location was well-mixed for 6 months and the central and northeast locations remained stratified into spring due to the lower initial surface salinities of the river-influenced water.
A 26 year record of ocean reanalysis highlights the region’s inter-annual variability of stratification and its dependence on winds and sea ice. Prior the mid-2000s, river runoff to the perennially ice-covered central Laptev Sea shelf experienced little surface forcing and river water was maintained on the shelf. The transition toward less summer sea ice after the mid-2000s increased the ROFI’s (region of freshwater influence) exposure to summer winds.
This greatly enhanced the
variability in mixed layer depth, resulting in several years with well-mixed water columns as opposed to the often year-round shallow mixed layers before. The extent of the Lena River plume is critical for the region since it modulates nutrient fluxes and primary production, and further controls intermediate heat storage induced by lateral density gradients, which has
implications for autumnal freeze-up and the eastern Arctic sea ice volume.
Summer winds increasingly control the extent of the region of freshwater influence under decreasing sea ice. Further reductions in sea ice will increase surface warming, heat storage, and the interannual variability in mixed layer depth."
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Surface waters properties in the Laptev and the East-Siberian Seas
in summer 2018 from in situ and satellite data
A Tarasenko et al 31 July 2019
https://os.copernicus.org/preprints/os-2019-60/os-2019-60.pdf free full text
Variability of surface water masses of the Laptev and the East-Siberian seas in August-September 2018 is studied using in situ and satellite data. In situ data was collected during ARKTIKA-2018 expedition and then completed with satellite estimates of sea surface temperature (SST) and salinity (SSS), sea surface height, satellite-derived wind speeds and sea ice concentrations. Derivation of SSS is still challenging in high latitude regions, and the quality of Soil Moisture and Ocean 5 Salinity (SMOS) SSS retrieval was improved by applying a threshold on SSS weekly error. The validity of SST and SSS products is demonstrated using ARKTIKA-2018 continuous thermosalinograph measurements and CTD cast.
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Surface waters properties in the Laptev and the East-Siberian Seas
in summer 2018 from in situ and satellite data
A Tarasenko et al 31 July 2019
https://os.copernicus.org/preprints/os-2019-60/os-2019-60.pdf free full text
Variability of surface water masses of the Laptev and the East-Siberian seas in August-September 2018 is studied using in situ and satellite data. In situ data was collected during ARKTIKA-2018 expedition and then completed with satellite estimates of sea surface temperature (SST) and salinity (SSS), sea surface height, satellite-derived wind speeds and sea ice concentrations. Derivation of SSS is still challenging in high latitude regions, and the quality of Soil Moisture and Ocean 5 Salinity (SMOS) SSS retrieval was improved by applying a threshold on SSS weekly error. The validity of SST and SSS products is demonstrated using ARKTIKA-2018 continuous thermosalinograph measurements and CTD cast
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Wind-Driven Coastal Upwelling near Large River Deltas in the Laptev and East-Siberian Seas
A Osadchiev et al 5 March 2020
https://doi.org/10.3390/rs12050844 free full text
“The Lena, Kolyma, and Indigirka rivers are among the largest rivers that inflow to the Arctic Ocean. Their discharges form a freshened surface water mass over a wide area in the Laptev and East-Siberian seas and govern many local physical, geochemical, and biological processes. In this study we report
coastal upwelling events that are regularly manifested on satellite imagery by increased sea surface turbidity and decreased sea surface temperature at certain areas adjacent to the Lena Delta in the Laptev Sea and the Kolyma and Indigirka deltas in the East-Siberian Sea. These events are formed under strong easterly and southeasterly wind forcing and are estimated to occur during up to 10%–30% of ice-free periods at the study region. Coastal upwelling events induce intense mixing of the Lena, Kolyma, and Indigirka plumes with subjacent saline sea.”
Freshwater transport between the Kara, Laptev, and East-Siberian seas
AA Osadchiev … IP Semiletov et al.
Scientific Reports (2020) 03 August 2020
https://phys.org/news/2020-09-scientists-freshwater-arctic-ocean.html popular account
https://www.nature.com/articles/s41598-020-70096-w free full text
"Russian researchers have investigated the spreading of large river plumes—that is, freshened water masses formed as a result of river runoff mixing with ambient saltwater—in the Russian Arctic seas. The Ob, Yenisei, and Lena rivers provide a huge volume of freshwater discharge to the Kara and Laptev seas. The total annual runoff from these three rivers is estimated at 2,300 cubic kilometers.
The majority of this volume is discharged into the sea during the ice-free season, forming the Ob-Yenisei plume and the Lena plume. River plumes are freshened water masses that form near river mouths and spread at sea as a relatively thin surface layer. River plume dynamics are mostly determined by wind forcing and river discharge rate.
in the absence of strong wind, the Coriolis force and the density gradient between the plume and the ambient seawater cause alongshore spreading of river plumes. That process induces a large-scale eastward freshwater transport that is observed in the Arctic Ocean along large segments of the Eurasian and North American shores. This feature strongly affects ice conditions in the region.
The study described in this article revealed how the Ob-Yenisei plume spreads from the Kara Sea to the Laptev Sea through the Vilkitsky Strait, which is located between the Severnaya Zemlya archipelago and the Taymyr Peninsula. The paper also addresses the Lena plume and its spreading from the Laptev Sea into the East Siberian Sea through the Laptev and Sannikov straits.
The authors demonstrated that continental runoff from the Ob and Yenisei mostly accumulates in the Kara Sea during the ice-free season. Topographic barriers—namely, the western coast of the Taymyr Peninsula and the Severnaya Zemlya archipelago—generally hinder eastward spreading of the Ob-Yenisei plume to the Laptev Sea. This process occurs only as a result of very specific wind forcing conditions.
On the contrary, the Lena plume is almost constantly spreading to the western part of the East Siberean Sea as a large-scale water mass, forming a narrow freshened coastal current in the eastern part of this sea. Known as the Siberian Coastal Current, it is intensified by freshwater runoff from the large Indigirka and Kolyma rivers and flows farther eastward to the Chukchi Sea.
Freshwater from the rivers flowing into the Arctic Ocean very slowly mixes with seawater, therefore the large river plumes are very stable. Freshwater can spread eastward across hundreds of kilometers, forced by local winds."