Patterns of forced decadal temperature variability over the last millennium in the tropics: perspectives from CMIP5 models and coral records
Abstract
A combination of internal ocean-atmosphere interactions and external forcing drives decadal-centennial scale tropical surface temperature variability in climate model simulations of the last millennium. Here we examine the patterns of decadal variability associated with external forcing in the CESM Last Millennium Ensemble and CMIP5 past1000 simulations. Specifically, we compare the relative magnitudes of decadal temperature variance in 20-year time slices before and after large volcanic eruptions in the CESM LME and CMIP5 past1000. We find that intermittent cooling from volcanic eruptions increases decadal-scale surface temperature variance in the tropical western Pacific, tropical Atlantic, and tropical Indian Oceans. A similar analysis conducted on coral-based reconstructions of low-latitude surface temperature does not show the same increase in decadal variability from external forcing relative to internal variability in these geographic regions. The discrepancy between observations and models could be due to uncertainties in the fidelity with which coral geochemical proxies record ocean surface temperature . This discrepancy could also be due to unrealistic simulation of decadal variability in climate models. Given the importance of the tropics for global climate variability, these results have implications for our understanding of the origins of forced and internal low-frequency climate variability. This work also has implications for decadal predictability of climate; if much of the tropical decadal variability is internal to the ocean-atmosphere system, then it may be easier to forecast than if unpredictable, short-lived cooling from volcanic eruptions drives this variability.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A21M2750P
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSES;
- 3339 Ocean/atmosphere interactions;
- ATMOSPHERIC PROCESSES;
- 4513 Decadal ocean variability;
- OCEANOGRAPHY: PHYSICAL;
- 4522 ENSO;
- OCEANOGRAPHY: PHYSICAL