A new paper has just been published by Richard Chiverrell and co-workers presenting the first Bayesian integration and modelling of all the dating control for the marine sectors of the largest ice stream that the last British-Irish Ice Sheet ~ 24,000 years ago. The modelling shows very rapid retreat for this marine-terminating ice stream over greater distances (650 km) and timescales (8000 years) than is available from short term (decadal) observations of present day ice stream margins. Current marine-terminating ice streams (e.g. Pine Island, West Antarctica) are also known to fluctuate rapidly, with significant concerns over the future rate of ice marginal retreat. Our modelling shows this retreat 24,000 years ago was rapid and linked with climatic warming, sea-level rise, mega-tidal amplitudes and reactivation of meridional circulation in the North Atlantic. But, significantly the pattern of retreat appears uneven with a pulsed pattern of retreat attributed to the passage of the ice stream between normal (sloping away from the ice margin) and adverse (sloping towards) ice bed gradients and changes in the geometry or marginal constriction of the ice stream.
So far no dataset for a retreating ice stream margin has been available to test patterns and rates of change over these millennial timescales relevant to significant distances of retreat >100 km. These data demonstrate the importance of the ice-bed slope and lateral extent for predicting ice marginal behaviour during phases of rapid collapse, and this has importance for present-day ice streams. Understanding of the behaviour of marine terminating ice streams during periods of rapid retreat is based on typically 30 years of monitoring data; the paper shows how ice stream geometry is critical over much longer timescales and for greater distances of retreat. The data reported potentially form validation material for ice sheet computer models that attempt to simulate the decline/collapse of marine terminating ice streams. To read more click here.
The methodology and application was an important test case for Britice-Chrono, a Natural Environment Research Council funded Consortium that over the next five years aims to constrain rates of and controls on marine ice stream retreat over millennial timescales for eight ice stream radiating out from the last British-Irish Ice Sheet. The methodology outlined in the paper will underpin and be used as a guide for our data collection for the wider British-Irish Ice Sheet.
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