Abstract
The rapid decline in Arctic sea ice poses urgent questions concerning its ecological effects, such as on tundra terrestrial productivity. However, reported sea ice/terrestrial productivity linkages have seldom been constrained, and the mechanism governing them remains elusive, with a diversity of spatial scales and metrics proposed, at times in contradiction to each other. In this study, we use spatially explicit remotely sensed sea ice concentration and high-resolution terrestrial productivity estimates (Normalised Difference Vegetation Index, NDVI) across the Svalbard Archipelago to describe local/sub-regional and large-scale components of sea ice/terrestrial productivity coupling. Whereas the local/sub-regional component is attributed to sea breeze (cold air advection from ice-covered ocean onto adjacent land during the growing season), the large-scale component might reflect co-variability of sea ice and tundra productivity due to a common forcing, such as large-scale atmospheric circulation (North Atlantic Oscillation, NAO). Our study clarifies the range of mechanisms in sea ice/terrestrial productivity coupling, allowing the generation of testable hypotheses about its past, present, and future dynamics across the Arctic.
Highlights
The steep decline in Arctic sea ice extent, concentration, and volume observed in recent decades has been linked to changes in tundra productivity[1,2,3,4,5,6,7]
Heterogeneous Correlation Maps depict the temporal linear correlation between the expansion coefficients of one field and each grid-point containing a timeseries of observations on the other field – see Methods, indicating how the two fields are related to one another and how much of the amplitude of their variation is explained by the Singular Value Decomposition (SVD), delivering information that hints at the nature of the coupling between the two fields[27]
In W-Sb, Normalised Difference Vegetation Index (NDVI) corresponding to vegetated land surface was found to be negatively related with sea ice, the relevant sea ice region was located in the northern Arctic Ocean, >250–300 km from most vegetated land masses: that is, sea ice conditions in the ocean sections adjacent to land were unrelated with NDVI, except for northernmost Spitsbergen (Reinsdyrflya, see Fig. 1a, Supplementary Material 1)
Summary
The steep decline in Arctic sea ice extent, concentration, and volume observed in recent decades has been linked to changes in tundra productivity[1,2,3,4,5,6,7]. AA consists of a suite of processes operating at northern high latitudes at different temporal and spatial scales[9] resulting in high rates of temperature variability and strong climate change trends in the Arctic These have been calculated to be ~1.6–2 times the global average in recent decades using observational climate data[10], and 3–4 times over longer term – millennia to millions of years – using proxy data[11]. Et al.[10] described large-scale (hemispheric) and local/sub-regional spatial components in AA The former is seen as the amplification of zonally averaged surface air temperature variations from tropical through high-latitude regions, whereas local/sub-regional AA was related to ice-albedo feedbacks in maritime and coastal areas in autumn when the ice cover is seasonally at a minimum[10]. (a) in the local/sub-regional AA, spatially-constrained sea ice adjacent to land will be highly related with onland terrestrial productivity;
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