Boundary layer models for calving marine outlet glaciers
We consider the flow of marine-terminating outlet glaciers that are laterally confined in a channel of prescribed width. In that case, the drag exerted by the channel side walls on a floating ice shelf can reduce extensional stress at the grounding line. If ice flux through the grounding line inc...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-10-01
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| Series: | The Cryosphere |
| Online Access: | https://www.the-cryosphere.net/11/2283/2017/tc-11-2283-2017.pdf |
| Summary: | We consider the flow of marine-terminating outlet glaciers that are laterally
confined in a channel of prescribed width. In that case, the drag exerted by
the channel side walls on a floating ice shelf can reduce extensional stress
at the grounding line. If ice flux through the grounding line increases with
both ice thickness and extensional stress, then a longer shelf can reduce
ice flux by decreasing extensional stress. Consequently, calving has an
effect on flux through the grounding line by regulating the length of the
shelf. In the absence of a shelf, it plays a similar role by controlling the
above-flotation height of the calving cliff. Using two calving laws, one due
to Nick et al. (2010) based on a model for
crevasse propagation due to hydrofracture and the other simply asserting
that calving occurs where the glacier ice becomes afloat, we pose and analyse
a flowline model for a marine-terminating glacier by two methods: direct
numerical solution and matched asymptotic expansions. The latter leads to a
boundary layer formulation that predicts flux through the grounding line as a
function of depth to bedrock, channel width, basal drag coefficient, and a
calving parameter. By contrast with unbuttressed marine ice sheets, we find
that flux can decrease with increasing depth to bedrock at the grounding
line, reversing the usual stability criterion for steady grounding line
location. Stable steady states can then have grounding lines located on
retrograde slopes. We show how this anomalous behaviour relates to the
strength of lateral versus basal drag on the grounded portion of the glacier
and to the specifics of the calving law used. |
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| ISSN: | 1994-0416 1994-0424 |