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The hydrography of the Arctic Ocean has experienced profound changes over the last two decades. The sea-ice extent has declined more than 10 % per decade, and its liquid freshwater content has increased mainly due to glaciers and sea ice melting. Further, new satellite retrievals of Sea Surface Salinity in the Arctic might contribute to better characterizing the freshwater changes in cold regions. That is because ocean salinity and freshwater content are intimately related such that an increase/decrease of one entails a decrease/increase of the other. In this work we evaluate the freshwater content in the Beaufort Gyre, using surface salinity measurements from the satellite radiometric mission Soil Moisture and Ocean Salinity (SMOS) and reanalysis salinity at depth. We estimate the freshwater content from 2011 to 2019 in the Beaufort Gyre and validate the results with in-situ measurements. The results highlight the underestimation of the freshwater content using reanalysis data in the Beaufort Sea and a clear improvement in the freshwater content estimation when adding satellite sea surface salinity measurements above the mixed layer. The improvements are significant, especially in areas close to ice melting. Our research demonstrates how remotely sensed salinity can assist us in better monitoring the changes in the Arctic freshwater content and improving our understanding of a key process that is creating subtle density differences that have the potential to change the global circulation system that regulates Earth’s Climate.

This report first develops an interpolation method for the Fram Strait mooring data. The resulting temperature sections are then compared with the acoustic data obtained during the ACOBAR experiment and are also used to assess the reliability of TOPAZ-4b in the Fram Strait. The last chapter links the temperature variability and trends observed in the Fram Strait with the circulation changes in the Nordic Seas and the Barents Sea and proposes an analysis of the underlying physical mechanisms.

VII Encuentro de Oceanografía Física (EOF) - Expanding Ocean Frontiers Conference, VIII International Symposium on Marine Sciences, 6-8 July 2022, Las Palmas de Gran Canaria, España, We have assessed the capability of Surface Quasi-Geostrophy (eSQG) to reconstruct the three-dimensional (3D) dynamics in two key areas of the Arctic Ocean: the Nordic and the Beaufort Seas. We reconstructed the upper ocean dynamics from sea surface height (SSH), surface buoyancy (SSB) and surface velocities and validated the results with the classical geostrophic and original TOPAZ reanalysis velocities. When compared to geostrophic velocities, the results demonstrated that the reconstruction of upper ocean dynamics using SSH fields is in high agreement, with correlation coefficients greater than 0.8 for the upper 400 m. SSH reconstructions outperforms surface buoyancy reconstructions also in places near freshwater inputs from river discharges, melting sea ice and glaciers. Surface buoyancy fails due to the uncorrelation of SSB and subsurface potential vorticity (PV). Reconstruction from surface currents correlates to TOPAZ velocities with correlation coefficients greater than 0.5 up to 200 meters. Due to a deeper thermocline and halocline, the performance of the eSQG approach is better in the fall and winter than in the spring and summer. Our results demonstrate that using only surface information from SSH or surface velocities, it is possible to effectively reconstruct upper ocean dynamics in the Arctic and Subarctic Seas up to 400 meters. Future remote sensing missions in the Arctic Ocean, like Seastar, WaCM, CIMR, and CRISTAL, will give improved and enhanced SSH and surface velocities observations, allowing SQG schemes to characterize upper ocean 3D dynamics

The inter-annual changes of the Arctic Ocean features are well-known proxies of the global climate change, affecting the global climate through specific processes (e.g. dense water formation, meridional heat redistribution). The ocean circulation at high latitudes has significantly changed during recent decades, with an enormous impact on the socio-economic activities of the Nordic populations. Monitoring the Arctic environment is however non-trivial: the Arctic observing network is notably lacking the capability to provide a full picture of the changing ocean due to technological and economical limitations to sample the seawater beneath the ice or in the marginal ice zones. This leads to the obvious need of optimizing the exploitation of data from space-borne sensors. Among these, altimetric radars measuring the sea level at millimetric precision have revolutionized our knowledge of the oceanic circulation, for more than 2 decades, at a large spectrum of scales ranging from the mesoscale activity to the slowly varying basin-wide dynamics. Technological solutions are continuously needed and pursued to enhance the spatial resolution of the altimetric signal and enable the solution of the mesoscale dynamics, either in the design of the altimeter itself (e.g. wide-swath altimeters) or in the combined use of altimeter data from multiple bands. Newly reprocessed along-track measurements of Sentinel-3A, CryoSat-2, and SARAL/AltiKa altimetry missions (AVISO/TAPAS), optimized for the Arctic Ocean (retracking) and sampled at 5 Hz, have been recently produced in the framework of CNES AltiDoppler project. This study is devoted to the exploitation of such satellite altimetry data in high-latitude regions. We investigate the benefits of the reprocessed altimetry dataset at 5 Hz with augmented signal resolution in the context of ocean and sea-ice coupled short-range forecasts. In particular, we compare the effectiveness of this dataset to improve the mesoscale details of the forecasts in comparison to the conventional altimetry sampling dataset and to the altimetry-blind experiments, in order to assess the added value of the enhanced altimetry reprocessing in Nordic Seas. This comparison can motivate the assimilation of the high-resolution altimetry data in ocean re-analysis for the Arctic.

European Space Agency Polar Science Collocation Meeting, 15-17 September 2021

Ocean Sciences Meeting (OSM), 16-21 February 2020, San Diego, CA, USA.- 1 figure, The warming of the Arctic air during summer is an increasingly frequent phenomenon. With surface air temperature exceeding more than 10ºC the mean of the last 40 years, and weekly average temperature values close to this peak value, the melt runoff in Greenland has dramatically increased. This phenomenon has reached its maximum expression in 2012 and 2019. The Greenland Ice sheet surface affected by melting has reached a maximum during these years (2012: 97%; 2019: 60%). The consequences of extreme ice melt episodes are critical not only for climate but also for coastal communities. As the temperature raise is caused by transient meteorological conditions (i.e. warm air systems coming from the South) the melting processes takes place suddenly and lasts only few days: from July 8 to July 12 in 2012 and from July 30 to August 3 in 2019. Nevertheless the huge amount of fresh water poured into the ocean can be detected by the drastic changes in the surrounding sea surface salinity. Not only continental ice melting should change the coastal sea surface salinity, but also the sea ice melting should reflect a freshwater anomaly along the ice field edge. ESA funded the Arctic+ salinity project which main objective is to retrieve Arctic sea surface salinity from Soil Moisture and Ocean Salinity (SMOS) mission measures. This new satellite salinity product provides remote sensing salinity measures in regions where insitu measures are very scarce and it offers an invaluable opportunity to study the ice melting simultaneously in the whole Arctic. Figure 1 shows preliminary evidences on the fact that this salinity product can resolve the increasing freshwater fluxes derived from continental and sea ice melting process. Figure 1.- Impact of melting process in sea surface salinity around Greenland and Severny island. The data correspond to 9-day maps centered on August 22, 2019 in the Severny island case and centered on July 15, 2012 for Greenland case. Left: Difference with salinity provided by the annual World Ocean Atlas during period 2005-2017. Right: Sea surface salinity retrieved from SMOS measures in the mentioned periods. Note that in Severny island case part of the freshwater bloom could be provided by Yenisey and Ob’ rivers discharges, Plain Language Summary. The warming of the Arctic air is an increasingly frequent phenomenon. This fact steps up the melting of the Arctic ice increasing the freshwater fluxes in the Arctic ocean. This fact has important consequences because the Arctic freshwater has influence in the position of the jet stream and in the northern weather systems. Moreover their consequences are critical not only for climate but also for coastal communities. In situ measures are scarce in the Arctic and remote sensing is a valuable tool to monitor Arctic processes. The melting ice can be detected by the decrease in salinity that takes place around it. This is especially true along the sea ice edge, but also for the continental ice because the melting runoff from glaciers diminishes the salinity of the coastal areas when freshwater mixes with sea water. Only 3 satellites have been devoted to measure sea surface salinity from space. This task is especially difficult in the Arctic due to the low temperature of sea water at high latitudes. A new satellite-based salinity product has been developed in the framework of the ESA Arctic+ salinity project and it will be used to detect and quantify the Arctic melting processes

VII International Symposium on Marine Sciences (ISMS 2020), 1-3 July 2020 (Barcelona).-- 2 pages, During the last 3 decades, the Arctic rivers have increased its discharge around10% mainly due the increase of temperature (Rawlins et al., 2010). The larger river discharge carries higher loads of dissolved organic matter (DOM) and suspended matter (SM) entering the Arctic Ocean. These results in increased absorption of solar energy inthe mixed layer potentially contributing to the general sea ice retreat (Soppa et al. 2019). Bauch et al., 2013 observed a correlation between river water discharge and local sea ice melting on the Laptev sea shelf, based on in-situ measurements, due to the change on the heat. New Arctic sea surface salinity products obtained from the ESA satellite SMOS (Soil Moisture and Ocean Salinity) have been improved considerable thanks to the ESA funded project Arctic+ Salinity. The maps have better accuracy and resolution so the salinity fronts are better resolved. These improved maps will permit for the first time to study scientific processes that have never been described up to now with satellite data. We will explore if a correlation between the Lena and Ob rivers discharge with the sea ice melting and freeze up is observed with satellite data, manly with the 9 years of SMOS data. Salinity and sea ice thickness maps from SMOS and sea ice concentration from AMSR2 satellite will be used in this study, Thanks to ESA for funding the Arctic+ Salinity Project