2,000-year-long temperature and hydrology reconstructions from the Indo-Pacific warm pool

Abstract

Northern Hemisphere surface temperature reconstructions suggest that the late twentieth century was warmer than any other time during the past 500 years and possibly any time during the past 1,300 years (refs 1, 2). These temperature reconstructions are based largely on terrestrial records from extra-tropical or high-elevation sites; however, global average surface temperature changes closely follow those of the global tropics, which are 75% ocean. In particular, the tropical Indo-Pacific warm pool (IPWP) represents a major heat reservoir that both influences global atmospheric circulation and responds to remote northern high-latitude forcings. Here we present a decadally resolved continuous sea surface temperature (SST) reconstruction from the IPWP that spans the past two millennia and overlaps the instrumental record, enabling both a direct comparison of proxy data to the instrumental record and an evaluation of past changes in the context of twentieth century trends. Our record from the Makassar Strait, Indonesia, exhibits trends that are similar to a recent Northern Hemisphere temperature reconstruction. Reconstructed SST was, however, within error of modern values from about ad 1000 to ad 1250, towards the end of the Medieval Warm Period. SSTs during the Little Ice Age (approximately ad 1550-1850) were variable, and approximately 0.5 to 1 degrees C colder than modern values during the coldest intervals. A companion reconstruction of delta(18)O of sea water-a sea surface salinity and hydrology indicator-indicates a tight coupling with the East Asian monsoon system and remote control of IPWP hydrology on centennial-millennial timescales, rather than a dominant influence from local SST variation.

A revised 1000 year atmospheric δ13C‐CO2 record from Law Dome and South Pole, Antarctica

“…CO 2 subsequently increases a little to 1650 A.D. but stays low until about 1750 A.D. This period of low CO 2 coincides with high ı 13 C interpreted by the KFDD as terrestrial uptake, which could be caused by a decrease of the Northern Hemispheric or global surface temperature [Mann et al, 2008;Oppo et al, 2009] Trudinger et al [1999] suggested that the lower temperature reduced both the release of CO 2 (soil respiration) and the uptake (photosynthesis) of CO 2 by the terrestrial biosphere, with the respiration reduction dominating, causing the terrestrial biosphere to accumulate carbon. Lower atmospheric CH 4 was found to be a likely result of land surface cooling during that period [Etheridge et al, 1998;Ferretti et al, 2006;Mitchell et al, 2011].…”

Holocene and Eemian sea surface temperature trends as revealed by alkenone and Mg/Ca paleothermometry

“…One example was provided in Oppo et al (2009) who reported some evidences for changes in the seasonality of G. ruber fluxes through time, with long-term (centennial-scale) oscillations between mean-annual temperatures and the July/August/September mean temperatures. This result is broadly consistent with the idea of long-term foraminifera sampling of boreal summer as we have suggested for this region.…”

Hydroclimatic shifts in northeast Thailand during the last two millennia – the record of Lake Pa Kho

“…Wang et al, 2005). Yet high-resolution tree ring , marine (Anderson et al, 2002;Newton et al, 2006;Oppo et al, 2009), coral (Cobb et al, 2003), speleothem (Sinha et al, 2011a;Zhang et al, 2008), and lake (Yancheva et al, 2007) studies show that substantial decadal to centennial variations in summer monsoon intensity were superimposed on the longterm trend. Various hypotheses have been brought forward through the last millennium Pages 2K, Consortium, 2013).…”