Water masses variability in the eastern Fram Strait explored through oceanographic mooring data and the CMEMS dataset

<p>The interaction between North Atlantic and Arctic Ocean waters plays a key role in climate variability and in<br>driving the global thermohaline circulation. In the past decades, an increased heat input to the Arctic has<br>occurred which is considered of high climatic relevance as, e.g., it contributes to enhancing sea ice melting.<br>In this frame, the progressive northward extension of the Atlantic signal within the Arctic domain known as<br>Arctic Atlantification is one of the most dramatic environmental local changes of the last decades.<br>In this study we used in situ data and the Copernicus Marine Environment Monitoring Service (CMEMS)<br>reanalysis dataset to explore spatial and temporal variability of water masses on different time-scales and<br>depths in the eastern Fram Strait. In that area, warm and salty Atlantic Water (AW) enters the Arctic Ocean<br>through the West Spitsbergen Current (WSC). Time series of potential temperature, salinity and potential<br>density obtained from CMEMS reanalysis in the surface, upper-intermediate and deep layers referring to the<br>period 1991-2019 have been considered. High-frequency observations gathered from an oceanographic<br>mooring maintained by the National Institute of Oceanography and Applied Geophysics (OGS) in<br>collaboration with the Italian National Research Council - Institute of Polar Science (CNR-ISP) have been<br>used to assess the reliability of CMEMS data in reproducing ocean dynamics in the deep layer (ca 900-1000<br>m depth) of the SW offshore Svalbard area. The mooring system has been collecting data since June 2014.<br>In this contribution, we will show how the CMEMS data compared with in situ measurements as far as<br>seasonal and interannual variations as well as long-term trends are concerned. We will also discuss how<br>CMEMS reanalyses show differences in resolving ocean dynamics at different depths. Particularly, the severe<br>limitations in reproducing thermohaline variability at depths greater than 700 m. Finally, we will illustrate how<br>our results highlight strengths and limitations of CMEMS reanalyses, underscoring the importance of<br>optimizing measurements in a strategic area for studying climate change impacts in the Arctic and sub-Arctic<br>regions.</p>