摘要：Various human activities, including fossil fuel combustion and forest clearing, emit about eight petagrams (or billion tons) of carbon in the form of CO 2 into the atmosphere annually. The global ocean absorbs about two petagrams of CO 2 , and about a half of that amount is absorbed by the Southern Ocean south of 30°S, thus slowing the rapid accumulation of CO 2 in the atmosphere. Partial pressure of CO 2 ( p CO 2 ) is a measure of the chemical driving force for the CO 2 exchange between the ocean and the atmosphere. This paper discusses its space and time distribution over the Southern Ocean. The major sink zone for atmospheric CO 2 is located in a latitude belt between 30°S and 50°S, where the biological utilization of CO 2 and cooling of warm subtropical waters flowing southward produce low seawater p CO 2 . Strong winds in this zone also enhance the ocean’s uptake. Although the source-sink conditions vary over a wide range through the seasons in the areas south of 50°S, this zone is a small sink on an annual average. Winter observations show that surface water p CO 2 values in the source region for Antarctic Intermediate Water have increased at a rate faster than the atmospheric increase rate, suggesting that the ocean CO 2 sink intensity has been weakening for several decades and has changed from a net sink to a net source since 2005. The results of ocean general circulation-biogeochemistry model studies are found to be consistent with the observations.
