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| Titel |
Multi-decadal decline in the formation of Antarctic Intermediate Water: a high-resolution model hindcast |
| VerfasserIn |
Eva Nowatzki, Lavinia Patara, Claus Böning, Johannes Karstensen |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250092484
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| Publikation (Nr.) |
 EGU/EGU2014-6835.pdf |
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| Zusammenfassung |
| We investigate the spatial and temporal variability of Antarctic Intermediate Water (AAIW)
formation rates, a process associated with substantial ocean uptake of heat and anthropogenic
CO2. To this end, we use a global configuration of the ocean general circulation model
NEMO-LIM at 1/4° resolution (ORCA025) to perform a 60-year simulation forced with
the CORE atmospheric reanalysis for the time period 1948-2007. A companion
simulation forced by a repeated annual cycle of atmospheric forcing is used to
correct for model spurious trends. The model is found to reproduce the main features
of AAIW, despite being somewhat biased towards higher core densities through
higher salinity and decreased northward propagation. The spatial distribution of
AAIW formation rates is explored via available AAIW volume and via kinematic
subduction rates. Maximum AAIW formation is found in the southeast Pacific and
along the Antarctic Circumpolar Current fronts in the Pacific and Indian Ocean
corresponding to mixed layer depth (MLD) winter maxima, whereas kinematic subduction
rates are highest in regions dominated by lateral induction. Over the 1948-2007
period, the largest temporal trends in MLDs, AAIW formation rates and kinematic
subduction rates are found in the southeast Pacific. Here, a strong negative MLD
trend is accompanied by a decrease in salinity at the mixed layer base. Both AAIW
formation rates and kinematic subduction rates show a similar decreasing trend in
the southeast Pacific, superimposed to a strong interannual variability in the case
of kinematic subduction rates. In the southwest Pacific, the negative trend is less
pronounced, the Indian and Atlantic Ocean do not show any trend. However, interannual
variability in the case of kinematic subduction rates is strong for all ocean basins. |
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