Atmospheric heat advection in the Kara Sea region under main synoptic processes

Abstract

Atmospheric studies document both a periodic variability in the winter temperatures in the Kara Sea region related to internal Arctic climate variability and a recent trend of winter warming—one of the strongest warming trends in the whole Arctic. This study aims to analyse side by side with other energy budget terms the contribution of horizontal heat and moisture advection to the observed recent warming. The atmospheric energy budget terms vertically integrated from the surface up to 500 hPa are estimated using the ERA‐Interim reanalysis for the period 1979–2014. The core of this study is to relate variability and changes in heat fluxes in the Kara Sea region to synoptic‐scale processes using the Russian weather‐type classification system. Singular spectrum analysis is applied to the heat flux data which were previously stratified into changes due to changes in frequency and due to changes in amplitude. We have shown that the multi‐decadal variations in the horizontal heat advection (now on a rising phase) are comparable to the positive trend in the turbulent heat fluxes due to sea ice reduction, although relatively weaker. We have also found that the changes in sensible heat flux (a constant increase in the first principal component since 1999) is a general regional feature and not related to any weather pattern, while the changes in horizontal heat advection are clearly related to the changes in frequency of the weather type A (characterized by a low‐pressure system in the central Arctic surrounded by high pressure in the continents, winds of S, S‐W direction and a positive horizontal heat advection and surface temperature anomaly over the Kara Sea) which are periodic in nature with a period of about 22 years. In recent years (at least until 2012) not only is warm air advection, associated with A type, more frequent, but it also brings much more energy from the continent to the Kara Sea compared to the reference period (1980–1990). This is most probably related to the increase in the radiatively forced surface air temperature at the source.