A Freshwater Starvation Mechanism for Dansgaard-Oeschger Cycles

• Main Authors: Hewitt, I.J., Wolff, E.W., Fowler, A.C., Clark, C.D, Evatt, G.W., Munday, D.R., Stokes, C.R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2015
• Subjects: 92 Hydrospheric and atmospheric geophysics; Arctic; Arctic Ocean; ice core; Ice Sheet; North Atlantic
• Online Access: http://eprints.maths.manchester.ac.uk/2304/1/do_paleo2-2.pdf

Ice core records indicate that the northern hemisphere underwent a series of cyclic climate changes during the last glacial period known as Dansgaard-Oeschger cycles. The most distinctive feature of these is a rapid warming event, often attributed to a sudden change in the strength of the Atlantic meridional overturning circulation (AMOC). We suggest that such a change may have occurred as part of a natural oscillation, which resulted from salinity changes driven by the temperature-controlled runoff from ice sheets. Contrary to many previous studies, this mechanism does not require large freshwater pulses to the North Atlantic. Instead, steady changes in ice-sheet runoff, driven by the AMOC, lead to a naturally arising oscillator, in which the rapid warmings come about because the Arctic Ocean is starved of freshwater. The changing size of the ice sheets, as well as changes in the background climate, would have aected the magnitude and extent of runoff, which altered the period and magnitude of individual cycles. We suggest that this may provide a simple explanation for the absence of the events during interglacials and around the time of glacial maxima.