Capturing the interactions between ice sheets, sea level and the solid Earth on a range of timescales: a new “time window” algorithm
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Published:2022-02-16
Issue:3
Volume:15
Page:1355-1373
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ISSN:1991-9603
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Container-title:Geoscientific Model Development
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language:en
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Short-container-title:Geosci. Model Dev.
Author:
Han Holly KyeoreORCID, Gomez NatalyaORCID, Wan Jeannette Xiu Wen
Abstract
Abstract. Retreat and advance of ice sheets perturb the gravitational field, solid
surface and rotation of the Earth, leading to spatially variable sea-level
changes over a range of timescales O(100−6 years), which in turn feed
back onto ice-sheet dynamics. Coupled ice-sheet–sea-level models have
been developed to capture the interactive processes between ice sheets, sea
level and the solid Earth, but it is computationally challenging to capture
short-term interactions O(100−2 years) precisely within longer O(103−6 years) simulations. The standard forward sea-level modelling algorithm
assigns a uniform temporal resolution in the sea-level model, causing a
quadratic increase in total CPU time with the total number of input ice
history steps, which increases with either the length or temporal resolution
of the simulation. In this study, we introduce a new “time window”
algorithm for 1D pseudo-spectral sea-level models based on the normal mode
method that enables users to define the temporal resolution at which the ice
loading history is captured during different time intervals before the
current simulation time. Utilizing the time window, we assign a fine
temporal resolution O(100−2 years) for the period of ongoing and
recent history of surface ice and ocean loading changes and a coarser
temporal resolution O(103−6 years) for earlier periods in the
simulation. This reduces the total CPU time and memory required per model
time step while maintaining the precision of the model results. We explore
the sensitivity of sea-level model results to the model temporal resolution
and show how this sensitivity feeds back onto ice-sheet dynamics in coupled
modelling. We apply the new algorithm to simulate sea-level changes in
response to global ice-sheet evolution over two glacial cycles and the rapid
collapse of marine sectors of the West Antarctic Ice Sheet in the coming
centuries and provide appropriate time window profiles for each application.
The time window algorithm reduces the total CPU time by ∼ 50 % in each of these examples and changes the trend of the total CPU time
increase from quadratic to linear. This improvement would increase with
longer simulations than those considered here. Our algorithm also allows for coupling
time intervals of annual temporal scale for coupled ice-sheet–sea-level
modelling of regions such as West Antarctica that are characterized by
rapid solid Earth response to ice changes due to the thin lithosphere and
low mantle viscosities.
Publisher
Copernicus GmbH
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