Independent annually diatom-inferred phosphorus and temperature reconstructions validated by instrumental records
by
S. Hausmann
Institute of Plant Sciences, University of Bern, Altenbergrain 21, CH-3013 Bern, Switzerland
Coauthors: F. Kienast (Swiss Federal Institute WSL, Zürcherstrasse, CH-8903 Birmensdorf, Switzerland)

In natural environments diatom distributions are driven by several parameters. Therefore, diatom-inferred temperature reconstructions can be biased by past e.g. nutrient changes.

This poster introduces a new approach to obtain independent quantitative reconstruction of climate and nutrients by stepwise reducing secondary gradients in the training-set. Independent WA-PLS diatom inference models for total phosphorus and July air temperature were established and applied on Greifensee sediment with annual resolution (1916 - 1995). The diatom-inferred July temperature and the independent diatom-inferred total phosphorus were validated by instrumental records. Greifensee was monitored for 40 years by EAWAG and the meteorological station supplied monthly temperatures for the studied time. The reduction of secondary gradients decreased the correlation between inferred temperature and observed total phosphorus (1954 - 1995) from rs=0.354 to rs=-0.005.

The relative abundances of the dominant fossil diatoms are significantly correlated to spring and autumn temperatures but not to July temperature as reconstructed. Consequently, the diatom-inferred July air temperature better reflects the observed spring air temperature than the observed July air temperature (1916 - 1995).

For future work a diatom inference model for temperature taking into account the seasonal succession of diatoms seems to be promising.

Keywords: diatoms, varves, WA-PLS, climate, nutrients, instrumental records

Date received: May 2, 2001

Copyright © 2001 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # cahi-72.