High Indian native Urban

Country/Region:

Andaman Islands, eastern Indian Ocean

Elevation:

-6

Archive:

corals

Species:

Porites lutea

Proxy measurement:

δ13C, δ18O

Sampling resolution:

monthly

Climate sensitivity:

SST, salinity

Dating resolution:

annual

Dating information:

annual cycle of d18O variations

Startyear:

1975 AD

Endyear:

2006 AD

Description:

North Atlantic climate variations are reflected in sedimentary records from the northern Indian Ocean in which two basins, the Arabian Sea and the Bay of Bengal, are strongly affected by the monsoon. Contrary to the Bay of Bengal the Arabian Sea plays an important role in the global marine nitrogen cycle. In its mid-water oxygen minimum zone (OMZ) bioavailable fixed nitrogen is reduced to nitrogen gas (NO3- -> N2), whereas oxygen concentrations are slightly above the threshold of nitrate reduction in the OMZ of the Bay of Bengal. A coral colony (Porites lutea) growing south of Port Blair on the Andaman Islands in the Bay of Bengal was studied for its response to changes in the monsoon system and its link to temperature changes in the North Atlantic Ocean, between 1975 and 2006. Its linear extension rates, d13C and d18O values measured within the coral skeleton reveal a strong seasonality, which seems to be caused by the monsoon-driven reversal of the surface ocean circulation. The sampling site appears to be influenced by low salinity Bay of Bengal Water during the NE monsoon (boreal winter) and by the high salinity Arabian Sea Water during the SW monsoon in summer. The high salinity Arabian Sea Water circulates along with the Summer Monsoon Current (S-MC) from the Arabia Sea into the Bay of Bengal. Decreasing d18O and reconstructed salinity values correlate to the increasing SSTs in the North Atlantic Ocean indicating a reduced influence of the S-MC at the sampling site in the course of northern hemispheric warming. During such periods oxygen-depletion became stronger in the OMZ of the Arabian Sea as indicated by the sedimentary records. A reduced propagation of oxygen-depleted high salinity Arabian Sea Water into the Bay of Bengal could be a mechanism maintaining oxygen concentration above the threshold of nitrate reduction in the OMZ of the Bay of Bengal in times of global warming.

Data entered by name:

Thorsten Kiefer

Data entered by email:

This email address is being protected from spambots. You need JavaScript enabled to view it.

Main reference(s):

Rixen, T., P. Ramachandran, L. Lehnhoff, D. Dasbach, B. Gaye, B. Urban, R. Ramachandran, and V. Ittekkot. 2010. Impact of monsoon-driven surface ocean processes on a coral off Port Blair on the Andaman Islands and their link to North Atlantic climate variations. Global and Planetary Change 75, 1–13. doi: 10.1016/j.gloplacha.2010.09.005

Link to reference 1:

http://www.sciencedirect.com/science/article/pii/S0921818110002006

Data storage link 1:

http://hurricane.ncdc.noaa.gov/pls/paleox/f?p=519:1:597046773068729::::P1_STUDY_ID:9639

Current dating method:

-- select --

Annual snow acc rate:

-- select --

Category: Ocean2k