A transition from the last glacial period, to the present interglacial period punctured by a brief and intense return to cold conditions around 10,900 years ago. Scientists believe this occurred because of the changes in atmospheric circulation resulting from large releases of melt water from glaciers. [Quaternary Science Reviews; v25; 3-4; 2006.] [Science; v315; 439; 2007.] [Palaeogeography, Palaeoclimatology, Palaeoecology; v246; 307-330; 2007.]