A part of the biosphere (such as a forest or ocean) that causes carbon dioxide to be removed from the atmosphere.
SDC, [Global Brief](https://www.eda.admin.ch/content/dam/deza/en/documents/publikationen/briefing-papers/global-brief-2013-03-baeume_EN.pdf), Trees to the Rescue of Climate and Development, March 2013 (23.02.2016).
([Oxford Dictionary of English\s, online edition, Oxford University Press 23.02.2016.](http://www.oed.com/view/Entry/27743?redirectedFrom=carbon+sink#eid10170506))