Project Details
Projekt
Bay of Bengal Replicate Coral Reconstructions and Tropical-Basin Interactions using Coral Data Assimilation: hydroclimate and temperature variability spanning the last centuries (HYDRA)
Applicant
Dr. Jessica Hargreaves
Subject Area
Geology
Term
since 2026
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 569233902
The greatest threat to coral reefs is the continued unabated increases in both atmospheric and oceanic temperatures. The temperature changes influence large-scale modes of climate variability and climate extremes, which across the tropics can impact millions of people. In the Indo-Pacific, these climate modes include, among others, the El Niño-Southern Oscillation, the Indian Ocean Dipole and the monsoon system. However, since large-scale ocean-atmospheric interactions vary on decadal to centennial time scales, the established short instrumental record is not sufficient to determine the full range of natural variability which, in turn, influences how well these conditions are realised in climate models. The assessment of past variability of sea surface temperature (SST), its links to hydroclimate and long-term variability of ocean-atmospheric modes of climate variability, is of critical importance and the basis for this proposal to the second phase of the programme, known as HYDRA. The initial focus of HYDRA is to fill a vital gap in coral proxy coverage, specifically across the Bay of Bengal, a region where observations of SST and salinity are patchy before the satellite era. This area's unique characteristics—high SST, low salinity, and strong stratification—lead to the development of low-pressure atmospheric systems, supporting large-scale convection associated with the monsoon system. Variability in the monsoon system have been linked to variability across the Indian Ocean, such as the size and intensity of the Mascarene High, phases of the Indian Ocean Dipole and the Indian Ocean Basin Mode. The new ultra-high-resolution coral reconstructions will provide a century-long intercolony replicate from a site open to the climatically dynamic Bay of Bengal. This SST reconstruction will cover the modern era, providing an essential extension of the short instrumental record, and will also provide a modern analogue for a snapshot intra-colony replicate reconstruction of the mid-Holocene of corals from the same location. The new modern reconstruction, along with efforts to develop a denser network of SST and seawater d18O, through the CoralHydro2k database will then be used to develop a climate field reconstruction, transforming site-specific reconstructions into a spatially resolved and multivariate perspective on climate through the last ~200 years. This will allow HYDRA to unravel complicated spatial variability of temperature and hydroclimate associated with dynamic inter-basin variability. The project will provide key answers for Indian Ocean rim countries which are directly impacted by increasing SST and extremes in hydrological variability, surrounding how long-term variability may change in a warming climate.
DFG Programme
Priority Programmes
International Connection
India
Cooperation Partner
Dr. Chitra Rajendran
