text: Together, the Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) act as a carbon sink, absorbing atmospheric carbon dioxide and storing it in solution. If the SAMW temperature increases as a result of climate change, the SAMW will have less capacity to store dissolved carbon dioxide. Research using a computerized climate system model suggests that if atmospheric carbon dioxide concentration were to increase to 860 ppm by the year 2100 (roughly double today's concentration), the SAMW will decrease in density and salinity. The resulting reductions in the subduction and transport capacity of SAMW and AAIW water masses could potentially decrease the absorption and storage of CO2 in the Southern Ocean.
  Flora and fauna
  Main: Category: Flora of subantarctic islands, and Category: Fauna of subantarctic islands.
  The Antarctic realm and Antarctic Floristic Kingdom include most of the subantarctic islands native biota, with many endemic genera and species of flora and fauna.
  Subantarctic island example
  The physical landscape and biota communities of Heard Island and McDonald Islands are constantly changing due to volcanism, strong winds and waves, and climate change. Volcanic activity has been observed in this area since the mid-1980s, with fresh lava flows on the southwest flanks of Heard Island. Satellite imagery shows that McDonald Island increased in size from about 1 to 2.5 square kilometers between 1994 and 2004, as a result of volcanic activity.
  In addition to new land being produced by volcanism, global warming of the climate is causing the retreat of glaciers on the islands (see section below ). These combined processes produce new ice-free terrestrial and freshwater ecoregions, such as moraines and lagoons, which are now available for colonization by plants and animals.