5. Januar 2011

2000-year-long temperature reconstruction from the Indo-Pacific warm pool

Vor kurzem bin ich auf eine interessante Studie von Oppo et al. gestoßen, welche Eindruck hinterlassen hat. Es handelt sich um die Arbeit 2,000-year-long temperature and hydrology reconstruction from the Indo-Pacific warm pool (pdf-Format, ca. 620 KB) aus dem Jahre 2009.

Der Grund dafür, dass ich diese doch schon nicht mehr ganz aktuelle Studie hervor"zaubere" ist, dass diese Studie um die südasiatische Äquatorialgegend (Indo-Pacific warm pool; Makassar Strait, Indonesia - lat. 0°/long. 116° E) lokalisiert ist. Dies rechtfertigt - wenn man die knapp bemessene Datengrundlage von Langzeitproxies für den Äquatorialraum berücksichtigt - in meinen Augen eine Anführung zum jetzigen Zeitpunkt.

Die Studienautoren beschreiben selbst sehr treffend, wie ich finde, die Notwendigkeit einer solchen Studie, wie folgt:
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[3], which are 75% ocean. In particular, the tropical Indo-Pacific warm pool (IPWP) represents a major heat reservoir that both influences global atmospheric circulation [4] and responds to remote northern high-latitude forcings[5,6].
 Oppo et al., 1113


Was wurde gemacht?
Here we present a decadally resolved continuous sea surface temperature (SST) reconstruction from the IPWP that spans the past two millennnia 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.
 Oppo et al., 1113


Was waren die für uns wichtigen Ergebnisse?
The SST reconstruction shows cooler temperatures between about AD 400 and AD 950 than during much of the so-called Medieval Warm Period (about AD 900–1300), a warm period found in many northern high-latitude records but whose global significance is uncertain[1].
Regardless of G. ruber* seasonality in this region, the reconstruction suggests that at least during the Medieval Warm Period, and possibly the preceding 1,000 years, Indonesian SSTs were similar to modern SSTs.
 Oppo et al., 1114


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[1] Jansen, E. et al. in Climate Change 2007: The Physical Science Basis (eds Solomon, S. et al.) 466–482 (Cambridge Univ. Press, 2007).
[2] Mann, M. E. et al. Proxy-based reconstructions of hemispheric and global surface temperature variations over the past two millennia. Proc. Natl Acad. Sci. USA 105, 13252–13257 (2008).
[3] National Research Council. Surface Temperature Reconstructions for the Last 2,000 Years (National Academy Press, 2006); available at http://www.nap.edu/catalog.php?record_id511676æ.
[4] Qu, T., Du, Y., Strachan, J., Meyers, G. & Slingo, J. Sea surface temperature and its variability in the Indonesian region. Oceanography 18, 50–61 (2005).
[5] Broccoli, A. J., Dahl, K. A. & Stouffer, R. J. Response of the ITCZ to northern hemisphere cooling. Geophys. Res. Lett. 33, doi:10.1029/2005GL024546 (2006).
[6] Chiang, J. C. H. & Bitz, C. M. Influence of high latitude ice cover on the marine Intertropical Convergence Zone. Clim. Dyn. 25, 477–496 (2005).

* Zur Erklärung: "To reconstruct d18O of sea water (SST and d18Osw), we generated Mg/Ca and d18O data on the planktonic foraminifera, Globigerinoides ruber (sensu stricto morphotype), which inhabits the surface mixed layer (Methods)." Oppo et al., 1114