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| Titel |
Improved GIA Correction and Antarctic Contribution to Sea-level Rise Observed by GRACE |
| VerfasserIn |
Erik Ivins, Thomas James, John Wahr, Ernst Schrama, Felix Landerer, Karen Simon |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250073733
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| Zusammenfassung |
| Measurement of continent-wide glacial isostatic adjustment (GIA) is needed to interpret
satellite-based trends for the grounded ice mass change of the Antarctic ice sheet
(AIS). This is especially true for trends determined from the Gravity Recovery and
Climate Experiment (GRACE) satellite mission. Three data sets have matured to
the point where they can be used to shrink the range of possible GIA models for
Antarctica: the glacial geological record has expanded to include exposure ages using
10Be,26Al measurements that constrain past thickness of the ice sheet, modelled
ice core records now better constrain the temporal variation in past rates of snow
accumulation, and Global Positioning System (GPS) vertical rate trends from across the
continent are now available. The volume changes associated with Antarctic ice
loading and unloading during the past 21 thousand years (21 ka) are smaller than
previously thought, generating model present-day uplift rates that are consistent with
GPS observations. We construct an ice sheet history that is designed to predict
maximum volume changes, and in particular, maximum Holocene change. This
ice sheet model drives a forward model prediction of GIA gravity signal, that in
turn, should give maximum GIA response predictions. The apparent surface mass
change component of GIA is re-evaluated to be +55 ± 13 Gt/yr by considering a
revised ice history model and a parameter search for vertical motion predictions
that best-fit the GPS observations at 18 high-quality stations. Although the GIA
model spans a wide range of possible earth rheological structure values, the data
are not yet sufficient for solving for a preferred value of upper and lower mantle
viscosity, nor for a preferred lithospheric thickness. GRACE monthly solutions from
CSR-RL04 release time series from Jan. 2003 through the beginning of Jan. 2012,
uncorrected for GIA, yield an ice mass rate of +2.9 ± 34 Gt/yr. A new rough upper
bound to the GIA correction is about 60-65 Gt/yr. The new correction increases
the solved-for ice mass imbalance of Antarctica to -57 ± 34 Gt/yr. The revised
GIA correction is smaller than past GRACE estimates by about 50 to 90 Gt/yr.
The new upper bound to sea-level rise from AIS mass loss averaged over the time
span 2003.0 - 2012.0 is about 0.16 ± 0.09 mm/yr. We discuss the differences in
spatio-temporal character of the gain-loss regimes of Antarctica over the observing period. |
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