Hydrographic responses to regional covariates across the Kara Sea

The Kara Sea is a shelf sea in the Arctic Ocean which has a strong spatiotemporal hydrographic variation driven by river discharge, air pressure and sea ice. There is a lack of information about the local scale effects of environmental variables to surface hydrography in different regions of the Kara Sea. We use a hierarchical spatially varying coefficient model to study the monthly variation of sea surface temperature (SST) and salinity (SSS) in the Kara Sea between years 1980 and 2000. The model allows us to study the effect of climatic (arctic oscillation index, AO) and seasonal (river discharge and ice concentration) environmental covariates on SST and SSS. The results show that the hydrographical response to environmental covariates vary considerably between different regions of the Kara Sea. River discharge decreases SSS in the shallow shelf area and has a neutral effect in the northern Kara Sea. The responses of SST to AO and river discharge vary in south-north direction. Ice concentration has the most constant effect across Kara Sea. We estimated also the average SST and SSS in the Kara Sea in 1980-2000. The average August SST over the Kara Sea in 1995-2000 was higher than the respective average in 1980-1984 with 99.9 % probability as SSS decreased with 77 % probability. We found a support that the winter season AO has an impact on the summer season hydrographical conditions, and decadal temporal trends may be related to the varying level of winter season AO index.