Sensitivity of Ice and Climate Evolution Patterns to Modelling Uncertainties During the Last Glacial-Interglacial Transitions

Abstract:

How did ice grow (volume, total area, extent) over North America (NA)
and Eurasia (EA) during inception? Did the ice-sheets grow and shrink
simultaneously, or each had its own inception time and maximum extent
and volume? How did the atmosphere respond to the changes in surface
albedo, altitude, dust concentration, and other feedbacks in the
system? And more interestingly, given the uncertainties in the
climate system, is there more than one way glacial inception and
deglaciation could happen? By exploring the sensitivity of the last
glacial inception and deglaciation to uncertainties in modelling such
as representation of radiative effect of clouds, initial state of the
ocean, downscaling and upscaling various climatic fields between the
atmospheric and ice model, and albedo calculation, we try to answer
these questions.

Therefore, we set up an ensemble of simulations for both inception and
deglaciation to investigate the extent to which such modelling
uncertainties can affect ice volume, area, and regional thickness
evolution patterns, in addition to various climatic fields, such as
the Rossby number, jet-stream location and strength, and sea-ice
expansion, during these two periods of interest. We analyze the
ensemble results to 1. investigate how important the parameters we
included in our ensemble can be in simulating glacial-interglacial
transitions, and 2. explore different possible patterns of the last
glacial inception and deglaciation.

The ensemble is set up using a fully-coupled Earth Model of
Intermediate Complexity, LOVECLIM, previously used in several
paleoclimate modelling studies, and a 3D thermo-mechanically coupled
ice sheet model. The coupled model is capable of simulating 1000
years in about 24 hours using a single core, making it possible to
accomplish an ensemble of 1000s of runs for both transition periods
within a few weeks.