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| Titel |
Effect of regional scale model coupling in simulating North Sea under a climate change scenario. |
| VerfasserIn |
Nikesh Narayan, Birgit Klein, Jian Su, Holger Klein |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250110189
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| Publikation (Nr.) |
 EGU/EGU2015-10166.pdf |
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| Zusammenfassung |
| Modeling climate change related alterations in North Sea is very challenging due to the sharp
changes in bottom topography, fresh water influx from the Baltic Sea and water mass
intrusions from the North Atlantic. Therefore, finding an ideal model setup which simulates
all the above conflicting factors is important and to attain this high resolution regional models
are often employed. When run in projection mode for a climate scenario their boundary
conditions have to be derived from coupled climate models which normally have coarser
resolution. These forcing fields are not necessarily in equilibrium with the regional
model set up and could result in model drift. We used the high resolution regional
model, HAMburg Shelf Ocean Model (HAMSOM) to study the changes in North
Sea under a climate change scenario. Two A1B scenario runs were simulated, one
in which the model was forced using the data from a global model (uncoupled)
and other in which the ocean model was fully coupled with an atmospheric model
(REMO). Comparison between the model simulations reveal that there is a significant
influence of coupling in simulating trends in physical parameters like temperature and
salinity of the North Sea. The coupled simulation tends to be warmer by about 1Ë
C by the end of 21St century when compared to the uncoupled simulation. This
change is very significant because it is almost half of the projected warming over
North Sea by the end of 21St century. The comparison of surface salinity values
from both simulations reveal that coupled model tend to be fresher especially in
the German Bight and Norwegian coastal current region. This also suggests that
there is a significant difference in simulating Baltic outflow/inflow between the two
simulations. The variability patterns of SST and SSS as revealed by time evolution
are identical in both simulations even with contrasting magnitudes. Independent
results from a global model with enhanced resolution over North Sea (including the
Baltic Sea) suggest strong freshening of North Sea especially in eastern coasts. The
uncoupled regional simulation does not reveal any such freshening, whereas the coupled
simulation shows a weak freshening of the coastal North Sea. The changes associated
with temperature and salinity could result in significant changes in the stratification
and influence ecosystem changes. The study will also focus on disentangling the
influence of natural variability and anthropogenic climate change on North Sea. |
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