Linda C. Ivany
Department of Earth Sciences
2011-12 European Tour Information
1-12 October 2012
GO TO: Biography| Abstract 1 | Abstract 2
Reconstructing paleoseasonality from accretionary biogenic carbonates – challenges and opportunities.
Seasonality of temperature variation has been somewhat of an enigma for paleoclimate research. The vast majority of studies on ancient climate purport to recover some approximation of ‘mean annual’ temperature, yet rarely is there any way to verify this. The unparalleled gold standard of climate records are those derived from the chemistry of marine microfossils, but unacknowledged seasonal differences in growth can give rise to biased mean values.
In addition, while mean annual temperature is a useful descriptor of climate, most organisms are limited instead by temperature extremes. Interpreting the impact of climate change on biological systems, often the ultimate goal of climate research, therefore requires knowledge of seasonal maxima and minima.
Lastly, seasonal range is a parameter that could be very useful in evaluating the results of climate models, but few data are available for comparison. Accretionary biogenic carbonates, such as the shells of fossil mollusks, offer an opportunity to recover seasonality in Earth’s deep past. High-resolution sampling along the growth trajectory can yield a detailed record of the temperatures experienced by an individual throughout some portion of its lifetime. Capturing a number of years within a particular stratigraphic horizon yields not only a robust measure of seasonal range but also information about interannual variability. With adequate coverage, both of these variables can be examined in a temporal or geographic context to see how they relate to changes in mean annual temperature as well.
The approach is not without its challenges – sampling resolution can smear the seasonal signal, organisms do not necessarily accrete carbonate throughout the year, and the depth at which benthic organisms live correlates roughly with the seasonal range they experience. Nevertheless, with a bit of care, these kinds of data can offer new insights on the climate system and the anticipated consequences of global change.