Air-sea CO_2 exchange of beach and near-coastal waters of the Chukchi Sea near Barrow, Alaska

摘要

Partial pressure of CO_2 in equilibrium with sample water (pCO_2) for the coastal water in the Chukchi Sea was continuously observed in summer, 2008. Average daily CO_2 flux calculated from the pCO_2 and gas transfer coefficients ranged from -0.144 to -0.0701gCm-2day-1 depending on which gas transfer coefficient was used. The pCO_2 before the landfast ice sheets melted appeared to be highly biologically controlled based on the following information: (1) the diurnal pattern of pCO_2 was strongly correlated with Photosynthetic Photon Flux Density (PPFD); (2) high chlorophyll density was observed during periods of peak uptake; and (3) the day-to-day variation in the pCO_2 strongly correlated with the presence or absence of near-shore ice sheets. The lowest pCO_2 of 35ppm together with the highest PPFD of 1362μmolEm~(-2)s~(-1) were observed in the afternoon on June 28 in the presence of sea ice. The very low pCO_2 observed in late June was likely caused by high photosynthetic rates related to high phytoplankton densities typically observed from spring to early summer near the ice edge, and by water low in salinity and CO_2 released by melting sea ice early in the season.