Abstract
ABSTRACTKey external forcing factors have been proposed to explain the collapse of ice sheets, including atmospheric and ocean temperatures, subglacial topography, relative sea level and tidal amplitudes. For past ice sheets it has not hitherto been possible to separate relative sea level and tidal amplitudes from the other controls to analyse their influence on deglaciation style and rate. Here we isolate the relative sea level and tidal amplitude controls on key ice stream sectors of the last British–Irish and Fennoscandian ice sheets using published glacial isostatic adjustment models, combined with a new and previously published palaeotidal models for the NE Atlantic since the Last Glacial Maximum (22 ka BP). Relative sea level and tidal amplitude data are combined into a sea surface elevation index for each ice stream sector demonstrating that these controls were potentially important drivers of deglaciation in the western British Irish Ice Sheet ice stream sectors. In contrast, the Norwegian Channel Ice Stream was characterized by falling relative sea level and small tidal amplitudes during most of the deglaciation. As these simulations provide a basis for observational field testing we propose a means of identifying the significance of sea level and tidal amplitudes in ice sheet collapse.
Highlights
Ice-ocean interactions are integral to some of the most important feedbacks modulating the global climate system and sea level
High spatial resolution palaeotidal simulations for NW Europe enable, for the first time, the influence of changing tidal amplitudes within specific ice stream sectors draining the British-Irish and Fennoscandian ice sheets to be analysed through time
The Celtic Sea, Galway Bay and Barra-Donegal sectors are characterized by megatidal amplitudes either during early, or middeglaciation, whereas the Minch Ice Stream is characterized by megatidal amplitudes during the final stages of deglaciation
Summary
Ice-ocean interactions are integral to some of the most important feedbacks modulating the global climate system and sea level. The presence of large tides in the vicinity of the Rutford Ice Stream in the Weddell Sea sector of Antarctica accounts for a 12 % increase in ice stream mean flow than would be the case without tides (Rosier et al, 2015). Both elastic (King et al, 2011) and viscoelastic (Gudmundsson, 2011) models have been able to simulate the influence of tides on ice stream velocities, the latter reproducing non-linear interactions. Increases in tidal amplitudes promote increased ice stream flow rates, iceberg calving, destabilise ice shelves, and the de-buttressing that results from ice shelf collapse promotes ice stream acceleration. Tides are integral to a series of positive feedbacks that promote ice sheet collapse with implications for global sea level (Hemming, 2004; Flückiger et al 2006)
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