Abstract
Abstract To inform the ongoing development of earth system models that aim to incorporate interactive ice, the potential impact of interannual variability associated with synoptic variability and El Niño–Southern Oscillation (ENSO) at the Last Glacial Maximum (LGM) on the evolution of a large continental ice sheet is explored through a series of targeted numerical modeling experiments. Global and North American signatures of ENSO at the LGM are described based on a multidecadal paleoclimate simulation using an atmosphere–ocean general circulation model (AOGCM). Experiments in which a thermomechanical North American ice sheet model (ISM) was forced with persistent LGM ENSO composite anomaly maps derived from the AOGCM showed only modest ice sheet thickness sensitivity to ENSO teleconnections. In contrast, very high model sensitivity was found when North American climate variations were incorporated directly in the ISM as a looping interannual time series. Under this configuration, localized transient cold anomalies in the atmospheric record instigated substantial new ice formation through a dynamically mediated feedback at the ice sheet margin, altering the equilibrium geometry and resulting in a bulk 10% growth of the Laurentide ice sheet volume over 5 kyr.
Highlights
High-frequency climate variability on the annual to subannual scale is reasonably well understood, there is an ongoing effort to account for observed low-frequency climate variability on interdecadal to millennial scales
Initial progress has been made by forcing thermomechanical ice sheet models (ISMs) with seasonally varying climatological fields derived from general circulation models (GCMs)
This method has proven to be instrumental in producing reconstructions of the Laurentide ice sheet at the Last Glacial Maximum (LGM) (e.g., Marshall et al 2002; Huybrechts et al 2004) and has been used to investigate the fate of the Greenland ice sheet (Otto-Bliesner et al 2006)
Summary
An and Wang 2005; van der Avoird et al 2002; Schneider and Comuelle 2005; Newman et al 2003), and in solid earth systems (e.g., Berger and von Rad 2005). It has become apparent from such studies that the influence of higher frequency processes on lowfrequency climate variability is often not well represented stochastically. There is a relative absence of high to low frequency coupled studies that deal with cryospheric processes This technique has considerable potential for untangling the dynamic history of massive continental ice sheets in the earth’s past since glacial inception (accumulation) and glacial demise (ablation)
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