Varying response of vegetation to sea ice dynamics over the Arctic

Recent reduction of sea ice may have contributed to vegetation growth over the Arctic through albedo feedback effects to atmospheric warming. Understanding the varying response of vegetation to sea ice dynamics is critical for predicting future climate change over the Arctic and middle-high latitudes. Instead of looking at the direct response characteristics, we perform a systematic analysis of the time-lag and time-cumulation responses of vegetation to sea ice dynamics, using a long-term Arctic Normalized Difference Vegetation Index (NDVI) dataset and three sea ice indices (sea ice concentration (SIC), sea ice area (SIA) and sea ice extent (SIE)) from 1982 to 2015. The results show that annual NDVI in the Arctic has exhibited a significant (p < 0.05) increase during 1982 to 2015, while a significant (p < 0.05) decrease is detected for annual SIC, SIA and SIE. The results of a regression analysis on NDVI identify a lag time of 7-months, 8-months and 9-months for vegetation response to SIC, SIA and SIE in February, March and April, respectively, while no evident lag response is observed in summer except for August. For the cumulation response, NDVI in February, March and April shows the largest response to the previous 5, 7 and 9 months of sea ice variations, respectively, while a short cumulation response of 1 to 3 months is found in summer. The differences in the spatial patterns of lagged time are usually not statistically significant in autumn and winter. A shorter lag response (1-3 month) is found in the Yamalia region in June. Further analysis suggests that vegetation response to sea ice dynamics depends on bio - climatic characteristics and soil pH, with vegetation responding faster to sea ice changes in acidic soil. This study provides observational evidences on the varying response of vegetation to sea ice dynamics over the Arctic, which has great implications for predicting vegetation-climate feedback and climate change.