Regime shift of the interannual linkage between NDVI in the Arctic vegetation biome and Arctic sea ice concentration

Abstract

Vegetation in the Arctic ecosystem is of particular interest due to its role in global carbon budgets and its feedbacks to the climate system. The variability of summer Arctic Normalized Difference Vegetation Index (NDVI) show a sudden change in 2010/2011. To explore the possible reasons, climatic variables in the ERA5 dataset are used in this research for statistical analyses, and numerical experiments based on ECHAM5 are performed to verify the results of statistical analyses. It is found that the relationship between Arctic NDVI and sea ice concentration (SIC) in north of the Barents Sea in March was not significant before 2009 (1982–2009, P1), but become stronger and statistically significant after 2010 (2010–2021, P2). The reason and the underlying mechanisms are then investigated as follows. The summer temperature, moisture condition, and atmospheric circulation corresponding to summer NDVI in P1 and P2 are different. These summer climatic anomalies associated with decreased SIC in north of the Barents Sea in March are similar to those associated with summer NDVI in P2, which are more favorable for higher summer NDVI in P2, whereas they differ substantially in P1. In P2, the net energy flux at the surface in spring exhibits more significant anomalies, indicating stronger sea-ice-atmosphere interactions in P2. Therefore, in P2, the significant anomalous Rossby wave in spring can propagates eastwards from the Barents Sea and interacts with the atmospheric circulation in the NDVI region. In spring, the precipitation, snowmelt, and soil moisture anomalies associated with decreased SIC in March can persist to summer, which can affect summer NDVI through soil moisture–evaporation–temperature positive feedback. However, in P1, the weaker sea-ice-atmosphere interaction associated with insignificant circulation and soil moisture anomalies in spring, which resulting in insignificant climatic anomalies for NDVI in summer. Numerical experiments using the ECHAM5 verify the proposed physical mechanisms.