Ocean2k's tropical SST synthesis

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PAGES’ Ocean2k Working Group has quadrupled the observational reach into tropical ocean temperature history in a recent open access synthesis paper in Paleoceanography entitled "Tropical sea surface temperatures for the past four centuries reconstructed from coral archives".

In this work, the Ocean2k High-Resolution Team compiled available coral records to reconstruct average sea surface temperatures for four major tropical regions thus extending the instrument-based record, previously limited to no more than a century, back to the year 1600 AD in the Indian, western Atlantic, and western and eastern Pacific oceans.

These new records allow temperature trends and the stability of decadal and interannual variability to be analysed across longer time periods.

 

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Figure 4 in article: Fourhundred-year histories of annual sea surface temperatures in four tropical ocean regions, based on reconstructions from geochemical coral records (blue) and on instrument-based SST from the Hadley Centre's HadISST dataset (in black). Portions of the reconstruction with no skill are gray.



With the exception of the eastern Pacific, tropical ocean temperatures were cooling prior to the mid-1800s, this was followed by warming at the rate of 0.03-0.04°C per decade. Exceptionally cool waters during the early 1800s in the Indo-Pacific region were likely due to dimming in response to several large tropical volcanic eruptions. The subsequent warming was initially probably due to the absence of major eruptions in the 20th century reinforced by greenhouse gas emissions.

Decadal-scale variability is a quasi-persistent feature of all of the basins. However, no evidence was found that either natural or anthropogenic forcings have systematically altered El Niño-Southern Oscillation (ENSO) tropical SST variance.

In the future these marine-based regional paleoclimate reconstructions will serve as benchmarks against which terrestrial reconstructions and climate model simulations can be compared and as a basis for studying the processes by which the tropical oceans mediate climate variability and change.


Reference

Tierney JE, Abram NJ, Anchukaitis KJ, Evans MN, Giry C, Kilbourne KH, Saenger CP, Wu HC & Zinke J (2015), Tropical sea surface temperature for the past four centuries reconstructed from coral archives, Paleoceanography. doi:10.1002/2014PA002717 (link)