Similarities between sea ice area variations and satellite-derived terrestrial biosphere and cryosphere parameters across the Arctic

Abstract. Satellite time series availability for the Arctic Ocean and adjacent land areas allows for cross-comparisons for cryosphere vs. vegetation parameters. Previous studies focused on correlation analyses between vegetation indices (derivatives of the normalized difference vegetation index (NDVI)) of tundra regions and sea ice extent for selected months. We have refined these analyses through consideration of distinct sea ice basins and all months, extension to south of the treeline, and included cryosphere essential climate variables such as snow water equivalent (SWE; March as proxy for annual maximum) and mean annual ground temperature (MAGT) in permafrost areas. The focus was on 2000–2019 considering data availability. As a first step, we derived trends. Changes across all the different parameters could be specifically determined for Eastern Siberia. Linkages between de-trended sea ice area (SIA) and NDVI across tundra regions was confirmed, where lower sea ice extent correlates with higher NDVI. The regional extension beyond the treeline revealed linkages for Northern European Russia and partially correlations of sea ice variations with land parameters over northern Scandinavia. Differences compared to previous studies ending in 2008 were found for the Kara Sea region and adjacent land area, indicating recent changes. In case of ground temperatures, high significant correlations were found for more distant sea ice basins than for NDVI, where the adjacent sea ice basins were more relevant. Negative and positive significant correlations can be found for March SWE depending on SIA month and region. Also, other months than September (sea ice extent minimum) were found to have high correlations vs. land-based variables, with distinct differences across sea ice basins. The fraction of data points with significant correlations north of 60° N is higher for SWE and MAGT than for the NDVI derivatives. Fractions for SWE are higher for Eurasia than Northern America. Autumn (incl. October and November) and mid-winter (incl. February, March) were most relevant for both investigated cryosphere-related parameters permafrost temperature and March snow water equivalent. Although similarities could be found between TI-NDVI and MaxNDVI, a higher proportion of significant correlations was observed for TI-NDVI. The datasets provide a baseline for future studies on common drivers of essential climate parameters and causative effects across the Arctic.