Apr 15, 2015

Icebergs not the trigger for North Atlantic cold events

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