 |
| Titel |
Past, present, and future changes in marine biogeochemistry in the Arabian Sea |
| VerfasserIn |
Katharina Six, Joachim Segschneider |
| Konferenz |
EGU General Assembly 2014
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250094943
|
| Publikation (Nr.) |
 EGU/EGU2014-10379.pdf |
|
|
|
|
|
| Zusammenfassung |
| The work presented here aims at a better understanding of the Asian Monsoon
system including the marine biogeochemistry in the Arabian Sea. Changes in the
past as recorded in marine sediments, as simulated over the past 1000 years, and
under forcing by anthropogenic CO2 emissions by numerical model simulations are
investigated. The investigation is based on three columns: a sediment core taken in the
Arabian Sea (core SO130-275KL taken off Pakistan), a pre-industrial model run
from 850 - 1850 with the Max Planck Institute’s Earth System Model (MPI-ESM)
including the marine and terrestrial carbon cycle and forced by solar variations
and volcanic eruptions, and a continuation of this simulation to 2005 under the
historical anthropogenic CO2 forcing which allows a comparison with present day
climatology.
In a first step we compare model results for a set of biogeochemical tracers within the
water column and the sediment mixed with observations in the Arabian Sea. We further
analyse correlations between Monsoon forcing (represented by zonal wind speed at 850 hPA,
short wave radiation, Indian summer precipitation) and biogeochemical parameters, with
particular focus on denitrification rates and fluxes to the sediment. This analysis is
focused on three regions: off Somalia and off Oman for the summer monsoon,
and the central Arabian Sea for the winter monsoon. For the summer monsoon,
the highest correlation is found between zonal wind speed and calcite flux to the
sediment off Somalia, for the winter monsoon the correlation is highest for short wave
radiation in the central Arabian Sea. Time series of mixed layer depth and integrated
primary production within the upper 100 m of the ocean from a CMIP5 historical
experiment (1850-2005) show, at the location of the sediment core SO130-275KL, little
correlation during the summer monsoon, but good correlation during the winter
monsoon. As a result, the sediment core is more likely to document winter monsoon
conditions.
Moreover, the model simulates denitrification in the oxygen minimum zones of the
Indian Ocean as expected. More interesting, when comparing pre-industrial, present,
and future states, it is shown that dentrification shows bipolar anomalies in the
present state with a positive anomaly in the eastern Arabian Sea, and a negative
anomaly in the western Arabian Sea. For 2100, when the model is forced by the
RCP8.5 scenario, anomalies of denitrification are negative in the entire Arabian Sea. |
|
|
|
|
|
|