Investigations of the Recent Climatic History of the Asian Monsoon
The project CARIMA ”Natural versus anthropogenic controls of past monsoon variability in Central Asia recorded in marine archives” is a subproject of the BMBF research programme CAME. CAME-“Central Asia and Tibet: Monsoon dynamics and geo-ecosystems" addresses recent climate change, geodynamics, geo-resources and geo-hazard potential (link: www.zentralasien.senckenberg.de). The main aim of CARIMA is to investigate monsoon impacts as well as effects caused by land use changes on weathering, marine biogeochemical processes, and the associated carbon storage in marine sediments of the northern Indian Ocean. We carry out a detailed study of the Late Holocene monsoon history, its natural variations and anthropogenic impacts using laminated cores from the northern and northwestern Arabian Sea (see Figure).
The monsoon region spans the tropics and subtropics of all continents and is generally defined by an annual reversal of surface winds with wet summers and dry winters. Changes in the effective solar radiation enforcing the land-ocean thermal contrast trigger natural variability of the monsoon and the northern hemispheric climate during the Holocene. In order to study monsoon as well as human impacts on the long-term carbon sequestration environmental reconstructions with high temporal resolution are required.
During the last years numerous and diverse monsoonal proxies have been established from long-term sediment traps and sediment core studies in the Arabian Sea. High productivity and sluggish reoxygenation of intermediate water masses have formed an oxygen depleted mid-water layer on the northern and western continental margins where even seasonal sediment layers (varves) are preserved. Thus, a multiproxy approach can discriminate between the signals of SW and NE monsoons and furthermore allows to study processes controlling marine carbon sedimentation as well as inputs of pre-aged former soil carbon into the ocean as well as their link to weathering on land.
The potential of the Arabian Sea as a monsoon archive is unique among the marine areas affected by the tropical or subtropical Asian monsoons. The archive’s resolution is well comparable to the records from lakes and tree rings, to monitor the transport of latent heat and water vapour towards central Asia that has a large impact on ecosystem stability, snow cover, land erosion as well as long-term carbon sequestration. Only recently, environmental reconstructions from the Arabian Sea have shown first evidence of a link between monsoon strength and anthropogenic development since the last 400 years. Past monsoon changes can be correlated to historical droughts in northern India and SW Tibet.
In work package 1 of CARIMA, integrating five German and one Indian research groups, we resolve the history of the NE- and SW-Monsuns using cores from the northern and northwestern slope, where the respective components of the Asian Monsoon system are of pronounced strength. Marine biogeochemical, micropaleontological and terrestrial geochemical proxies are combined to a unique record. Age control is provided by varve counting, AMS-dating and cross-correlation of records on centennial to annual timescales. Proxy validation and further development is extended to aerosol forcing and reconstruction of ancient land cover by dust sampling in India and sediment sampling in dust source areas around the Arabian Sea by the Indian partner. Results are correlated to terrestrial records and used to force the global bioeochemical model HAMOC.
Partners of WP1 (Arabian Sea):
- Institut für Biogeochemie und Meereschemie, Universität Hamburg (Anna Böll, Dr. Birgit Gaye)
- Institut für Geowissenschaften (IFGTÜ), Eberhard-Karls-Universität Tübingen (Philipp Munz, Dr. Hartmut Schulz)
- Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), Referat Meeresgeologie (Dr. Andreas Lückge)
- Leibnizzentrum für Marine Tropenökologie (ZMT), Bremen und Institut für Biogeochemie und Meereschemie, Universität Hamburg (Sven Forke, Dr. Tim Rixen).
- Max-Planck-Institut für Meteorologie (Dr. Joachim Segschneider, Dr. Katharina Six)
- National Institute of Oceangraphy, Goa, India (Dr. V. Ramaswamy)
Partners of WP2 (Bay of Bengal; South China Sea).
- Zentrum für Marine Umweltwissenschaften (MARUM), Universität Bremen
- Fachbereich Geowissenschaften, Universität Bremen
- Leibnizzentrum für Marine Tropenökologie (ZMT), Bremen
Duration of the Project 2011-2014
Information about the project at the IfBM: Birgit Gaye
Presentations and Publications
Gaye, B. “CARIMA – Arabian Sea Sedimentation as a Monitor of the Asian Monsoon System in Historical Times”. HIMPAC Kickoff meeting “Modern and Palaeomonsoons”, 27.-29.06.2011, Geoforschungszentrum Potsdam.
Böll. A., B. Gaye. A high resolution 2000 year record of monsoon variability in the Arabian Sea. Poster presentation at “EGU General Assembly 2012” in Vienna.
Böll. A. and B. Gaye. Monsoonal climate variability in the Arabian Sea during the late Holocene. “International Conference of the Geologische Vereinigung and SEDIMENT” in Hamburg, 25.-27.09. 2012
Gaye, B., A. Böll, J. Möbius, T. Rixen V. Ramaswamy. Fluctuations in denitrification and upwelling in the Arabian Sea during the recent geological history “International Conference of the Geologische Vereinigung and SEDIMENT” in Hamburg, 25.-27.09. 2012.
Gaye, B. Monsoon Reconstructions from Marine and Terrestrial Archives. Sustained Indian Ocean Biogeochemsitry and Ecosystem Research, SIBER-3 Meeting, Capetown 15-20 October 2012.
Böll, A., B. Gaye and A. Lücke. Late Holocene SST and productivity variations in the NE Arabian Sea as a recorder for winter monsoon variability. Poster at the EGU General Assembly, Vienna, 2014.
Böll, A. and B. Gaye. Sea surface temperature variations in then northeastern Arabian Sea as a recorder for Asian climate variability during the last two millennia. Poster, OSM 2014, Honolulu, USA.
Böll, A., Lückge, A., Munz, P., Forke, S., Schulz, H., Ramaswamy, V., Rixen, T., Gaye, B., Emeis, K.-C., 2014. Late Holocene primary productivity and sea surface temperature variations in the northeastern Arabian Sea: Implications for winter monsoon variability. Paleoceanography 29, doi:10.1002/2013PA002579.