Science Source

Stephen Barker, James Chen, Xun Gong, Lukas Jonkers, Gregor Knorr, David Thornalley

Nature

Published date April 15, 2015

Icebergs not the trigger for North Atlantic cold events

Results reveal the intimate association between ice rafting and high-latitude temperature variability over the last four glacial cycles with unprecedented detail
Cites previous studies that identified an apparent lag between North Atlantic cooling events and the appearance of ice-rafted debris over the last glacial cycle, leading to the hypothesis that iceberg discharge may be a consequence of stadial conditions rather than the cause
Further establishes this relationship and demonstrates a systematic delay between pronounced surface cooling and the arrival of ice-rafted debris at a site southwest of Iceland over the past four glacial cycles, implying that in general icebergs arrived too late to have triggered cooling
Suggests abrupt transitions to stadial conditions should be considered as a nonlinear response to more gradual cooling across the North Atlantic
Finds that although the freshwater derived from melting icebergs may provide a positive feedback for enhancing and or prolonging stadial conditions, it does not trigger northern stadial events.
Findings suggest that stadial transitions may occur as a nonlinear response to more gradual cooling, implying the existence of a threshold beyond which the transition to a stadial state becomes inevitable