Dr. Mahyar Mohtadi is a palaeooceanographer and palaeoclimatologist specializing in past climate change with an emphasis on the mid- and low-latitude climate, particularly in the following areas: Western Pacific Warm Pool hydrology, past climate of the Indonesian Archipelago and East Asian monsoon variability. He is currently a Senior Scientist at the Center of Marine Environmental Sciences (MARUM), University of Bremen, Germany. Dr. Mohtadi is author and co-author of over 40 articles in scientific journals such as Nature, Nature Geoscience, PNAS and Paleoceanography.
Results from one decade of research on past Indonesian climate, particularly the trends and variability in hydrological cycle and its forcing mechanisms are discussed. Consistent with instrumental and historical records, solar forcing, ENSO, and the position of the rainbelt largely control the Holocene climate variability of Indonesia. The role of volcanic forcing and the Indian Ocean Dipole remain to be explored in future studies and require climate archives with very high temporal resolution, such as corals, stalagmites or varve sediments that are not yet available. Large differences exist between the hydroclimate of the deep tropics and the monsoon regions at various timescales, owing to the different feedbacks of these regions to the same, or a combination of forcing mechanisms. Records off Sumatra suggest a gradual drying trend over the course of the Holocene that reverses during the past 2000 years, while records from the monsoonal Indonesia show no trend during the Holocene but an abrupt two-step increase at about 3000 and 1000 years ago. Records from northern and eastern Indonesia are equivocal and do not show a coherent change over the Holocene and the past 2000 years, owing to different local feedback mechanisms and a limited understanding of the present and past behavior of the proxies used for hydroclimate reconstructions. A deeper understanding of these proxies is essential for a more reliable projection of future changes in Indonesian hydroclimate.