Derivation of bedrock topography measurement requirements for the reduction of uncertainty in ice-sheet model projections of Thwaites Glacier
<p>Determining the future evolution of the Antarctic Ice Sheet is critical for understanding and narrowing the large existing uncertainties in century-scale global mean sea-level-rise (SLR) projections. One of the most significant glaciers and ice streams in Antarctica, Thwaites Glacier, is at...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-03-01
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| Series: | The Cryosphere |
| Online Access: | https://tc.copernicus.org/articles/16/761/2022/tc-16-761-2022.pdf |
| Summary: | <p>Determining the future evolution of the Antarctic Ice
Sheet is critical for understanding and narrowing the large existing
uncertainties in century-scale global mean sea-level-rise (SLR) projections.
One of the most significant glaciers and ice streams in Antarctica, Thwaites
Glacier, is at risk of destabilization and, if destabilized, has the
potential to be the largest regional-scale contributor of SLR on Earth. This
is because Thwaites Glacier is vulnerable to the marine ice-sheet
instability as its grounding line is significantly influenced by
ocean-driven basal melting rates, and its bedrock topography retrogrades
into kilometer-deep troughs. In this study, we investigate how bedrock
topography features influence the grounding line migration beneath Thwaites
Glacier when extreme ocean-driven basal melt rates are applied.
Specifically, we design experiments using the Ice-sheet and Sea-level System
Model (ISSM) to quantify the SLR projection uncertainty due to reported
errors in the current bedrock topography maps that are often used by
ice-sheet models. We find that spread in model estimates of sea-level-rise
contribution from Thwaites Glacier due to the reported bedrock topography
error could be as large as 21.9 cm after 200 years of extreme ocean warming.
Next, we perturb the bedrock topography beneath Thwaites Glacier using
wavelet decomposition techniques to introduce realistic noise (within
error). We explore the model space with multiple realizations of noise to
quantify what spatial and vertical resolutions in bedrock topography are
required to minimize the uncertainty in our 200-year experiment. We conclude
that at least a 2 km spatial and 8 m vertical resolution would independently
constrain possible SLR to <span class="inline-formula">±2</span> cm over 200 years, fulfilling
requirements outlined by the 2017 Decadal Survey for Earth Science. Lastly,
we perform an ensemble of simulations to determine in which regions our
model of Thwaites Glacier is most sensitive to perturbations in bedrock
topography. Our results suggest that the retreat of the grounding line is
most sensitive to bedrock topography in proximity to the grounding line's
initial position. Additionally, we find that the location and amplitude of
the bedrock perturbation is more significant than its sharpness and shape.
Overall, these findings inform and benchmark observational requirements for
future missions that will measure ice-sheet bedrock topography, not only in
the case of Thwaites Glacier but for Antarctica on the continental scale.</p> |
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| ISSN: | 1994-0416 1994-0424 |