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| Titel |
Earth system component responses under LGM boundary conditions in HadGAM2 |
| VerfasserIn |
Peter Hopcroft, Paul Valdes, Nicola Gedney |
| 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 |
250083629
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| Zusammenfassung |
| In this work we use the atmospheric and terrestrial components of the Earth System model
HadGEM2-ES to explore the sensitivity of vegetation, the mineral dust cycle and wetland
methane emissions under boundary conditions relevant to the last glacial maximum (LGM)
relative to the pre-industrial (PI). For the LGM we configured HadGAM2 with LGM
greenhouse gas concentrations, 21kyr ice sheets, orography and sea level and 21kyr orbital
parameters. For the PI and LGM simulations HadGAM2 was forced with sea surface
temperatures and sea-ice cover from equivalent coupled atmosphere-ocean HadCM3
simulations. We have also optionally prescribed vegetation distributions simulated with
HadCM3M2 which employs the TRIFFID vegetation model (this model is also used within
HadGAM2).
In HadGAM2 the LGM-PI temperature change is generally similar to that found in
HadCM3, though it is found to be more extreme over Asia, where feedbacks from snow cover
and changes in vegetation enhance the local signal. The dust model is sensitive to changes in
the bare soil fraction, with particularly large emissions changes over South America and
Australia. The globally averaged radiative forcing from mineral dust changes is consistent
with the higher end of the range found in previous studies, ranging from -0.4Wm-2
for no vegetation change to -1.7Wm-2 with prescribed HadCM3M2 vegetation
distributions.
The HadGEM2 methane emission model is used both online and offline in a number of
different configurations in order to address uncertainty in the model formulation. A subset of
the model versions considered suggests a completely source driven change in atmospheric
CH4 at the LGM relative to the PI, consistent with recent modelling studies of the
atmospheric composition at the LGM. Future work will consider the sensitivity of
these HadGAM2 Earth System components to SST and sea-ice area perturbations. |
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