A spaceborne assessment of cyclone impacts on Barents Sea surface temperature and chlorophyll

摘要

A pilot satellite-based investigation of modulations exerted upon mixed-layer phytoplankton fields by cyclones was performed for the first time across a selected part of the Arctic Ocean, the Barents Sea (BS). Resorting to a synergistic approach, cyclones were first identified from NCEP/NC.R data for the summer period during 2003-2013, and their propagation throughout the BS was further surveyed. The above-water wind force was retrieved from QuikSCAT data. These data were further accompanied by ocean colour data from SeaWiFS and MODIS to examine the spatial and temporal distributions of surficial phytoplankton chlorophyll concentration (chl) dynamics along the trajectory of the cyclone's footprint across the sea. Sea surface temperature was retrieved from MODIS data. The specific trajectory of cyclone passage across the BS area, depression depth, and wind speed proved to be conjointly the main factors determining the sign, amplitude, and duration of modulations of phytoplankton chl. The spaceborne data obtained over more than a decade indicate that, on balance, the cyclone passage led to increase in chl within the cyclone footprint area. On average, this increase did not exceed 1-2 mu g l(-1), which is nevertheless appreciable given that the mean chl within the cyclone footprint rarely exceeded 1 mu g l(-1). However, chl enhancement within the footprint area lasted only within the range of a few days to a fortnight, with the footprint area generally accounting for about 14% of the BS area. During the vegetation season (April-August, rarely till mid-September), the number of cyclones prone to optical and infrared remote sensing was about 2-3. In light of the above, arguably the cyclones studied are hardly capable of boosting annual primary productivity in the BS. Moreover, it can be conjectured that the same conclusion can be drawn with respect to the pelagic Arctic tracts that are generally less productive and more extensively cloud-covered than the BS. However, this supposition requires further studies in order to advance our understanding of the actual role of cyclones in modulation of Arctic Ocean productivity and ecosystem functioning.