Seasonal Forcing of Summer Dissolved Inorganic Carbon and Chlorophyll a on the Western Shelf of the Antarctic Peninsula

摘要

The Southern Ocean is a climatically sensitive region that plays an important role in the regional and global modulation of atmospheric CO(2). Based on satellite-derived sea ice data, wind and cloudiness estimates from numerical models (National Centers for Environmental Prediction-National Center for Atmospheric Research reanalysis), and in situ measurements of surface (0-20 m depth) chlorophyll alpha (Chl(Surf)) and dissolved inorganic carbon (DIC(Surf)) concentration, we show sea ice concentration from June to November and spring wind patterns between 1979 and 2006 had a significant influence on midsummer (January) primary productivity and carbonate chemistry for the Western Shelf of the Antartica Peninsula (WAP, 64 deg-68 deg S, 63.4 deg-73.3 deg W). In general, strong (greater than 3.5 m s(-1)) and persistent (greater than 2 months) northerly winds during the previous spring were associated with relatively high (monthly mean is greater than 2 mg m(-3)) Chl(Surf) and low (monthly mean is less than 2 mmol kg(-1)) salinity-corrected DIC (DIC(Surf*)) during midsummer. The greater Chl(Surf) accumulation and DIC(Surf*) depletion was attributed to an earlier growing season characterized by decreased spring sea ice cover or nearshore accumulation of phytoplankton in association with sea ice. The impact of the wind-driven mechanicms on Chl(Surf) and DIC(Surf*) depended on the extent of sea ice area (SIA) during winter. Winter SIA affected phytoplankton blooms by changing the upper mixed layer depth (UMLD) during the subsequent spring and summer (December-January-February). Midsummer DIC(Surf*) was not related to DIC(Surf*) concentration during the previous summer, suggesting an annual replenishment of surface DIC during fall/winter and a relatively stable pool of deep (greater than 200 m depth) 'winter-like' DIC on the WAP.