TY  - THES
A1  - Schlemm, Tanja
T1  - The marine ice cliff instability of the Antarctic ice sheet
T1  - Die marine Eisklippeninstabilität des antarktischen Eisschildes
BT  - a theory of mélange-buttressed cliff calving and its application in the Parallel Ice Sheet Model
BT  - eine Theorie des Mélange-gebremsten Klippenkalbens und ihre Anwendung im Parallel Ice Sheet Model
N2  - The Antarctic ice sheet is the largest freshwater reservoir worldwide. If it were to melt completely, global sea levels would rise by about 58 m. Calculation of projections of the Antarctic contribution to sea level rise under global warming conditions is an ongoing effort which
yields large ranges in predictions. Among the reasons for this are uncertainties related to the physics of ice sheet modeling. These
uncertainties include two processes that could lead to runaway ice retreat: the Marine Ice Sheet Instability (MISI), which causes rapid grounding line retreat on retrograde bedrock, and the Marine Ice Cliff Instability (MICI), in which tall ice cliffs become unstable and calve off, exposing even taller ice cliffs.
In my thesis, I investigated both marine instabilities (MISI and MICI) using the Parallel Ice Sheet Model (PISM), with a focus on MICI.
N2  - Der antarktische Eisschild ist das größte Süßwasserreservoir der Welt. Würde er vollständig schmelzen, würde der globale Meeresspiegel um etwa 58 m ansteigen. Die Ermittlung von Prognosen über den Beitrag der Antarktis zum Anstieg des Meeresspiegels infolge der globalen Erwärmung ist ein fortlaufender Prozess, der große Unterschiede in den Vorhersagen zur Folge hat. Einer der Gründe dafür sind Ungewissheiten im Zusammenhang mit der Physik der Eisschildmodellierung. Zu diesen Unsicherheiten gehören zwei Prozesse, die zu einem unkontrollierten Eisrückzug führen könnten:
die Marine Ice Sheet Instability (MISI), die zu einem schnellen Rückzug der Grundlinie auf rückläufigem Grundgestein führt, und die Marine Ice Cliff Instability (MICI), bei der hohe Eisklippen instabil werden und abkalben, wodurch noch höhere Eisklippen freigelegt werden.
In meiner Dissertation untersuchte ich beide marinen Instabilitäten (MISI und MICI) mit Hilfe des Parallel Ice Sheet Model (PISM), wobei der Schwerpunkt auf MICI lag.
KW  - Antarctica
KW  - ice sheet modelling
KW  - iceberg calving
KW  - Antarktis
KW  - Eisschildmodellierung
KW  - Eisbergkalbung
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-586333
ER  - 
TY  - JOUR
A1  - Schlemm, Tanja
A1  - Feldmann, Johannes
A1  - Winkelmann, Ricarda
A1  - Levermann, Anders
T1  - Stabilizing effect of melange buttressing on the marine ice-cliff instability of the West Antarctic Ice Sheet
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - Owing to global warming and particularly high regional ocean warming, both Thwaites and Pine Island Glaciers in the Amundsen region of the Antarctic Ice Sheet could lose their buttressing ice shelves over time. We analyse the possible consequences using the parallel ice sheet model (PISM), applying a simple cliff-calving parameterization and an ice melange-buttressing model. We find that the instantaneous loss of ice-shelf buttressing, due to enforced ice-shelf melting, initiates grounding-line retreat and triggers marine ice sheet instability (MISI). As a consequence, the grounding line progresses into the interior of the West Antarctic Ice Sheet and leads to a sea level contribution of 0.6 m within 100 a. By subjecting the exposed ice cliffs to cliff calving using our simplified parameterization, we also analyse marine ice cliff instability (MICI). In our simulations it can double or even triple the sea level contribution depending on the only loosely constrained parameter that determines the maximum cliff-calving rate. The speed of MICI depends on this upper bound of the calving rate, which is given by the ice melange buttressing the glacier. However, stabilization of MICI may occur for geometric reasons. Because the embayment geometry changes as MICI advances into the interior of the ice sheet, the upper bound on calving rates is reduced and the progress of MICI is slowed down. Although we cannot claim that our simulations bear relevant quantitative estimates of the effect of ice-melange buttressing on MICI, the mechanism has the potential to stop the instability. Further research is needed to evaluate its role for the past and future evolution of the Antarctic Ice Sheet.
Y1  - 2022
U6  - https://doi.org/10.5194/tc-16-1979-2022
SN  - 1994-0416
SN  - 1994-0424
VL  - 16
IS  - 5
SP  - 1979
EP  - 1996
PB  - Copernicus
CY  - Göttingen
ER  -