Alkenone Paleotemperature Measurements

Organic geochemistry provides a promising proxy to reconstruct ocean surface temperatures.

Alkenones are long-chained ketones synthesized by a limited number of haptophyte algal species; their unsaturation ratio (determined by gas chromatography) has been show both mechanistically and statistically to yield very good estimates of the growth temperature. Because these organisms must live in the photic zone, their growth temperature is closely tied to SST. The alkenone method sidesteps ambiguities inherent in using planktonic d¹⁸O and/or faunal assemblages as a paleotemperature proxies, as both can be influenced by variables other than near surface temperature. The most widely used calibration of unsaturation index to temperature is the linear model of Prahl et al. (1988):

T = ( U^k' ₃₇ - 0.039)/0.034

Our laboratory is highly automated, and can extract and analyze 100- 120 samples per week. Expertise from Professors Prell (planktonic foraminifera, stable isotopes) and Huang (organic geochemistry) complement our alkenone paleotemperature efforts.
Current projects include:

• re-evaluating the stability of the tropical sea surface temperatures during the past ice ages


• studying regional variations in temperatures during glacial terminations


• using the alkenone index to resolve past decadal to century-scale changes in the Peru and California margin upwelling zones


• documenting SST variability over the past 5 Ma

Brown faculty collaborators:

None

Other project collaborators: