On the Relation between the Shrinking of Sea Ice Coverage and Climate Warming in the Marine Arctic

The Arctic amplification (AA) of climate warming is understood as the excess of the rise of the surface air temperature (SAT) in the Arctic over the same process in the non-Arctic latitudes, and it is a fundamental characteristic of the climate during periods of warming. The positive feedback between albedo and shrinking of the sea ice coverage has been identified as the first possible cause of AA. This article presents quantitative estimates of the relationship between the summer decrease and autumn–winter restoration of the ice coverage with the rise of the SAT in the marine Arctic based on data of observations. The mean monthly values of the temperature in the marine Arctic and the mean monthly values of areas covered by the sea ice in the Arctic Ocean and the Arctic seas for the period 1989–2020 are used. It has been found that the warming and the decrease in the ice coverage are accompanied by a growth of intermonthly changes in the coverage and the same in the air temperature. Negative trends in increments of the ice coverage in May–July is indicative of a long-term growth in intermonthly shrinkage of the ice coverage due to increasing melting, while negative trends in increments of the temperature in the same months is suggestive of a slowdown in the temperature rise from month to month, presumably due to the increasing heat consumption for the snow and ice melting and the water heating. The positive correlation confirms the relation between growing negative intermonthly differences in the ice coverage and decreasing positive differences in the air temperature during these months. Based on that, we determine the sensitivity of the intermonthly increments of the temperature to the increments of the ice coverage, which was used to estimate the weakening of the positive air temperature trend in May–July over the Arctic Ocean and over the seas of the Northern Sea Route (NSR). It becomes difficult to estimate the relationship between month-to-month changes in temperature and ice coverage in the autumn–winter months due to the strong influence of external heat influx. Only in November and January has a slowdown in the air temperature drop from October to November and from December to January been revealed, with a positive trend in the ice coverage increments. A relationship is found between the increase in the intermonthly summer reduction and autumn–winter recovery of ice cover and intermonthly changes in SAT in the maritime Arctic based on observations for 1989–2020. Based on this, it is determined that the positive trend in the average air temperature over the Arctic Ocean and over the seas of the NSR in May–July decreased and increased in November and January.