| Summary: | The Arctic has been warming two to four times more rapidly than the global mean in the last decades – a phenomenon known as Arctic Amplification. This warming induces changes for the whole cryosphere, including the permafrost and the Arctic sea ice. Using reanalysis data (ERA5-Land) has shown that the freezing of the upper soil of the active layer of the permafrost is happening later now than in the past, lengthening the period of carbon emissions. The timing of the drop below 0 °C of the 2 m air temperature has been identified has the principal driver of that delay. While Arctic Amplification is a likely driver of those long-term changes, it is unclear what controls the permafrost variability on shorter time scales. The hypothesis is formulated that sea ice concentration plays a role through the atmospheric circulation on the air temperature in Arctic, and thus on the permafrost degradation. This study aims to evaluate if rapid sea ice loss events – events where the sea ice concentration is way lower than expected according to the climatology during several years – impacts the onset and the duration of the late shoulder season (season between plant senescence and active layer freezing) of the permafrost. These events are expected to happen more in the future, with summer regularly ice-free from 2050 on. The potential link between sea ice concentration and permafrost may thus have a great impact on the Arctic environment, now and in the future. To evaluate that link, temperature, precipitation and geopotential anomalies (deviations from the average of the height of a surface pressure (here 500 hPa), that allow an evaluation of the atmospheric circulation) in PanArctic permafrost regions are studied in relation to sea ice concentration. Our preliminary results indicate that the September sea ice extent might have an effect on the 2m air temperature on the surrounding land, especially in the Eurasian Arctic, and thus influence the permafrost of those regions. Studying the influence of Arctic sea ice on air ...
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