 |
| Titel |
Terrigenous discharge of the Ganges-Brahmaputra River and productivity changes in the Gulf of Bengal on millennial to orbital time scales during the past 100 kyr |
| VerfasserIn |
C. Rühlemann, J. Fenner |
| Konferenz |
EGU General Assembly 2009
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250029788
|
|
|
|
|
|
| Zusammenfassung |
| High-resolution paleoclimate records from the Indian Monsoon area show remarkable
similarity with the abrupt temperature variations found in Greenland ice cores (e.g., Schulz et
al., 1998; Kudrass et al., 2001, Altabet et al., 2002). In general a strong monsoon (strong SW
winds, high precipitation, high sea surface temperatures) is associated with warm phases in
the North Atlantic.
Sediment core SO188-342KL (19Ë 58’N, 90Ë 02´E, 1256 m, sedimentation rate of ca. 10
cm kyr-1), recovered from the northern Gulf of Bengal, ~200 km south of the
Ganges-Brahmaputra mouth, is ideally suited to monitor climate fluctuations in the
river’s catchment area and the Gulf waters on Dansgaard/Oeschger (D/O) time
scales. For North Atlantic interstadials high resolution XRF measurements of Ti/Ca
ratios indicate increased river suspension load due to strengthened precipitation
and continental erosion. Chlorin abundance (a chlorophyll-α degradation product)
determined from photospectrometric reflectivity measurements covering the past 100
kyr and siliceous microfossil counts for the past 15 kyr show millennial events
superimposed on orbital-scale variations. The close correspondence with the Ti/Ca
record suggests that maxima in terrigenous supply and nutrient discharge to the
northern Gulf coincide with increased paleoproductivity. The Bengal fan is the largest
submarine sediment fan of the world and an important depocenter for organic carbon.
Although primary production rates in the northern Gulf of Bengal are relatively low
(20-180 g C m-2 yr-1 at the eastern Indian shelf and 30-80 g C m-2 yr-1 in the open
ocean) organic carbon sediment accumulation rates (0.5 to 2 g C m2 yr-1) are
comparable to those of eastern boundary upwelling areas. The high terrigenous fluxes
accelerate the transport of organic carbon to the seafloor and cause high burial rates. The
low frequency (orbital) paleoproductivity changes found in core SO188-342KL
show an inverse relationship with the atmospheric CO2 oscillations observed in
Antarctic ice cores between 20 and 60 kyr ago. We therefore speculate that variations
in marine paleoproductivity and associated carbon burial in the Bengal fan may
have contributed to the atmospheric CO2 changes during the last glacial period. |
|
|
|
|
|
|