An Abrupt Shift in the Indian Monsoon 4,000 Years Ago

The emergence of high-resolution proxy records from the Asian Monsoon region suggest that the monsoon system is bistable and can abruptly transition between a suppressed and active state. This observation is critical in considering how the monsoon system may have in the development of societies across India and Asia during the Holocene. Using a new high resolution (5 years/sample) proxy record from Northeast India that spans the early and mid-Holocene, a number of abrupt changes in the isotopic com2 position of precipitation (d18Op) are documented. The most dramatic of these events occurred 4,000 years ago when over the course of a approximately a decade, isotopic values precipitously rose above any seen during the Holocene and remained at this elevated state for almost two centuries. This event occurs nearly synchronously with climatic changes documented in a number of proxy records across North Africa, the Middle East, Southern Europe and perhaps as far as central North America. The changes in d18Op were likely driven by a dynamical response of the monsoon to changes in surface heating on the Tibetan Plateau and/or large-scale Ocean dynamics in the Indian Ocean Basin. At this point, a quantitative interpretation of the change in monsoon is hindered by unconstrained aspects of the regional response of d18Op to climate but we hypothesize the excursion could represent a shift towards an earlier monsoon onset (or withdrawal), a more northerly vapor source region or a weakening of the monsoon.

BERKELHAMMER Max;  SINHA A.;  STOTT L.;  CHENG H.;  PAUSATA Francesco;  YOSHIMURA K.; 

2014-10-07

AMERICAN GEOPHYSICAL UNION

JRC67069

978-0-87590-488-7,   

0065-8448,   

http://onlinelibrary.wiley.com/book/10.1029/GM198,    https://publications.jrc.ec.europa.eu/repository/handle/JRC67069,   

10.1029/GM198,