Using Paleoclimatology and Foraminifera to Better Understand Modern Climate Variability

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Monday, 5 January 2015
Rebecka M. Hastings, South Dakota School of Mines and Technology, Rapid City, SD

While our current understanding of the natural variability in the global climate system is progressively increasing, it is still critically limited in both temporal and spatial coverage. Increased datasets, both in time and space, would provide greater insight into the complexities of Earth's climate system and variability, thus providing more reliable interpretations and predictions of future climate processes. While scientists began collecting an instrumental record of climate conditions back in the mid-19th century, it was not common practice until the mid- to late-20th century. As a result, instrumental records give scientists, at best, approximately 150 years worth of data. Unfortunately, this record is not long enough to comprehensively understand Earth's complex and multifaceted climate system, which encompasses cycles that can take place seasonally to annually or on orders of magnitude anywhere from hundreds to tens of thousands of years, and anywhere in between. The field of paleoclimatology is the key to acquiring these increased temporal and spatial datasets and gaining a better understanding of Earth's climate variation. Paleoclimatologists utilize natural environmental proxies which record and preserve past climate conditions. Fortunately, these paleoclimate proxies have a global distribution that can be found in almost anything, e.g., buried in ocean and lake sediments, locked in glaciers, preserved in tree rings, etc. As a result, these archives have temporal and spatial coverage previously unparalleled with instrumental records.

Foraminifera are one such archive that has the potential of unlocking many key components of the climate system, both in the long and short term. Foraminifera are single celled protists found buried in lake and ocean sediments that have the potential of providing climatological data all over the planet and extending millions of years into the past. However, they are often overlooked from a meteorological standpoint because they are not what one would think of as a traditional ‘instrument' for recording climate variability. Foraminifera are, in fact, an excellent instrument in recording sea-surface temperature, precipitation and evaporation, ocean salinity, global ice volume, atmospheric chemistry, carbon cycling, ocean productivity, carbon exchange between the air and sea, etc. Depending on the variable in question, this data is obtained through planktonic and benthic fossil assemblages, and by geochemical analyses via the dissolution of the foraminifera's CaCO3 test (shell). Scientists then analyze the Mg/Ca ratios and the stable isotopes of oxygen (d 18O), carbon (d 13C), and boron (d 11B) with a mass spectrometer in order to extract the aforementioned variables. As a result, foraminifera have the potential to provide a natural paleo baseline for which climatologists could compare and calibrate climate forecast models with instrumental records. By incorporating both instrumental and paleoclimatological data, scientists can gain a truly comprehensive look at how Earth's climate system has changed over the past few years to millennia, and a far better understanding about what causes these modifications and what the implications are for the future, near and far.