Climate change impacts on sea–air fluxes of COsub2/sub in three Arctic seas: a sensitivity study using Earth observation

摘要

We applied coincident Earth observation data collected during 2008 and 2009from multiple sensors (RA2, AATSR and MERIS, mounted on the European SpaceAgency satellite Envisat) to characterise environmental conditions andintegrated sea–air fluxes of CO₂ in three Arctic seas (Greenland,Barents, Kara). We assessed net CO₂ sink sensitivity due to changes intemperature, salinity and sea ice duration arising from future climatescenarios. During the study period the Greenland and Barents seas were netsinks for atmospheric CO₂, with integrated sea–air fluxes of?36 ± 14 and ?11 ± 5 Tg C yr?1, respectively, and theKara Sea was a weak net CO₂ source with an integrated sea–air flux of+2.2 ± 1.4 Tg C yr?1. The combined integrated CO₂ sea–airflux from all three was ?45 ± 18 Tg C yr?1. In a sensitivityanalysis we varied temperature, salinity and sea ice duration. Variations intemperature and salinity led to modification of the transfer velocity,solubility and partial pressure of CO₂ taking into account the resultantvariations in alkalinity and dissolved organic carbon (DOC). Our resultsshowed that warming had a strong positive effect on the annual integratedsea–air flux of CO₂ (i.e. reducing the sink), freshening had a strongnegative effect and reduced sea ice duration had a small but measurablepositive effect. In the climate change scenario examined, the effects ofwarming in just over a decade of climate change up to 2020 outweighed thecombined effects of freshening and reduced sea ice duration. Collectivelythese effects gave an integrated sea–air flux change of +4.0 Tg C in theGreenland Sea, +6.0 Tg C in the Barents Sea and +1.7 Tg C in the KaraSea, reducing the Greenland and Barents sinks by 11% and 53%,respectively, and increasing the weak Kara Sea source by 81%. Overall,the regional integrated flux changed by +11.7 Tg C, which is a 26%reduction in the regional sink. In terms of CO₂ sink strength, weconclude that the Barents Sea is the most susceptible of the three regions tothe climate changes examined. Our results imply that the region will cease tobe a net CO₂ sink in the 2050s.