Extension of Pacific summer waters in the Arctic Ocean based on field and model data

During the last few decades we observe fast climatic changes. These changes are well expressed in the Polar Region that is more sensitive to all environmental shifts. The temperature and salinity anomalies were observed not only on the surface but also in the Pacific origin halocline layer. Due to hydrostatic imbalance and atmospheric circulation, water from the North Pacific flows through the Bering Strait, transits the upper levels of the Arctic Ocean, and penetrates to the North Atlantic. Pacific Summer Water (PSW) (flows through the Bering Strait in summer) is a main freshwater source in the Canadian Basin and influences thermohaline structure of the whole Arctic Ocean. Based on the field oceanographic data obtained during 1991-2014 we found the high interannual variability of PSW extent and maximum temperatures of PSW core. Since 1991 the area of PSW distribution decreased and the boundary of PSW extension shifted from the Makarov Basin towards the Canada Basin. At the end of the 2000s the PSW boundary extension returned to approximately early 1990s conditions. Rapid changes in the Arctic wind forcing regime occurred in 2007 led to anomaly extension of the PSW boundary towards the Lomonosov Ridge in 2008. For study the distribution of PSW under the conditions of a lack of field data, we used the modeling data of the GLORYS12V1 product of Copernicus Marine Environment Monitoring Service (http://marine.copernicus.eu/). The model component is the NEMO platform driven at the surface by ECMWF ERA-Interim reanalysis. Based on the calculated data we revealed the maximum temperatures and extension of PSW core in the Arctic Ocean from 1993 to 2018. As a result of comparing of field and calculated data, we found a good correspondence the values of maximum temperatures and the position of the PSW core in the centre of the Canada Basin. For example, in 2011 observed (1.0 °С) and calculated (0.9 °С) maximum temperature of PSW were very close. Based on model data we calculated the heat content of PSW which reached maximum values in recent years. The research was supported by the Ministry of Science and Higher Education of the Russian Federation (project RFMEFI61619X0108).