Unravel causes for the changing behavior of tropical Indian Ocean in the past few decades

Unravel causes for the changing behavior of tropical Indian Ocean in the past few decades AbstractObservations show that decadal (10-20yrs) to inter-decadal (>20yrs) variability of tropical Indian Ocean (TIO) sea surface temperature (SST) closely follows that of the Pacific until the 1960s. Since then, the TIO SST exhibits a persistent warming trend, whereas the Pacific SST shows large-amplitude fluctuations associated with the Inter-decadal Pacific Oscillation (IPO), and the decadal variability of TIO SST is out-of-phase with that of the Pacific after ~1980. Here we explore causes for the changing behavior of the TIO SST, by analyzing multiple observational datasets and the recently available large-ensemble simulations from two climate models.We find that on inter-decadal timescales, the persistent TIO warming trend is caused by emergence of anthropogenic warming overcoming internal variability, while the time of emergence occurs much later in the Pacific. On decadal timescales, two major tropical volcanic eruptions occurred in the 1980s and 1990s cause decadal SST cooling over the TIO, during which the IPO was in warm phase, yielding the out-of-phase relation. The more evident fingerprints of external forcing in the TIO compared to the Pacific result from the much weaker TIO internal decadal to inter-decadal variability, making the TIO prone to the external forcing. These results imply that the ongoing warming and natural external forcing may make the Indian Ocean more active, playing an increasingly important role in affecting regional and global climate. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Climate American Meteorological Society

Unravel causes for the changing behavior of tropical Indian Ocean in the past few decades

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Publisher
American Meteorological Society
Copyright
Copyright © American Meteorological Society
ISSN
1520-0442
D.O.I.
10.1175/JCLI-D-17-0445.1
Publisher site
See Article on Publisher Site

Abstract

AbstractObservations show that decadal (10-20yrs) to inter-decadal (>20yrs) variability of tropical Indian Ocean (TIO) sea surface temperature (SST) closely follows that of the Pacific until the 1960s. Since then, the TIO SST exhibits a persistent warming trend, whereas the Pacific SST shows large-amplitude fluctuations associated with the Inter-decadal Pacific Oscillation (IPO), and the decadal variability of TIO SST is out-of-phase with that of the Pacific after ~1980. Here we explore causes for the changing behavior of the TIO SST, by analyzing multiple observational datasets and the recently available large-ensemble simulations from two climate models.We find that on inter-decadal timescales, the persistent TIO warming trend is caused by emergence of anthropogenic warming overcoming internal variability, while the time of emergence occurs much later in the Pacific. On decadal timescales, two major tropical volcanic eruptions occurred in the 1980s and 1990s cause decadal SST cooling over the TIO, during which the IPO was in warm phase, yielding the out-of-phase relation. The more evident fingerprints of external forcing in the TIO compared to the Pacific result from the much weaker TIO internal decadal to inter-decadal variability, making the TIO prone to the external forcing. These results imply that the ongoing warming and natural external forcing may make the Indian Ocean more active, playing an increasingly important role in affecting regional and global climate.

Journal

Journal of ClimateAmerican Meteorological Society

Published: Dec 20, 2017

References

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