One More Alarmist Claim Not Supported by the Latest Science -- Fears of a Permanent El Nino
Ivany, L. C., Brey, T., Huber, M., Buick, D.P., and Schöne, B.R. 2011. El Niño in the Eocene greenhouse recorded by fossil bivalves and wood from Antarctica. Geophysical Research Letters 38: L16709, doi:10.1029/2011GL048635.
The investigators develop their proxy records using climate-sensitive variations in annual growth widths in the shells of two long-lived fossil bivalves, Cucullaea raea and Eurhomalea antarctica, and in associated (co-occurring) driftwood from the Antarctic Peninsula. [Bivalves are molluscs with two hinged shells, e.g., clams, oysters, mussels, and scallops.] The fossil bivalves were recovered from shallow marine sediments off Seymour Island, which is off the northeastern tip of the Antarctic Peninsula. The driftwood was from a coniferous tree on the Peninsula. The samples were dated using biostratigraphy and strontium isotope stratigraphy. So what did they find?
The investigators note that variations in annual growth increments for both the fossil bivalves and driftwood were similar in frequency to those observed in current day bivalves due to ENSO. They note that Antarctica currently experiences the effects of ENSO via atmospheric and oceanic teleconnections citing among others, Harangozo (2000), Yuan (2004), and Ding et al. (2011). They also note that although the Drake Passage between Antarctica and South America was closed in the early Eocene, "Seymour Island was in essentially the same position relative to the Pacific Ocean as it is today." They then theorize that "if ENSO operated during the Eocene, its effects would be felt along the Antarctic Peninsula and would be evident in the growth rates of long-lived, suspension-feeding bivalves." They also note that there is theoretical support from Eocene climate modeling that ENSO existed during that epoch.
The authors conclude by noting that their data supports other studies that find ENSO-scale oscillations in much warmer worlds than today, which indicates that the permanent ENSO state was not omnipresent during those periods. This result, they note, is "counter to predictions of a permanent El Niño and suggest that ENSO is a robust feature of the climate system that will persist into the warmer world of our collective future."
Ding, Q., Steig, E.J., Battisti, D.S. and Kuttel, M. 2011. Winter warming in West Antarctica caused by central tropical Pacific warming, Nature Geoscience 4: 398-403.
Harangozo, S.A. 2000. A search for ENSO teleconnections in the west Antarctic Peninsula climate in Austral winter. International Journal of Climatology 20: 663-679.
Yuan, X. 2004. ENSO-related impacts on Antarctic sea ice: A synthesis of phenomenon and mechanisms. Antarctic Science 16: 415-425.