Using a new network of isotopes of precipitation within the United States (USNIP) to better understand mid-latitude isotope-climate relationships
PhD: University of Colorado Boulder, 2006.
Climate change is a topic on the minds of scientist, politicians and agriculturalists alike. Recent climate events have made apparent our vulnerability to its effects. In order to approximate future climates we have to better understand the mechanisms that drove past climate changes.
Thus far we have a few hundred years of quantifiable meteorological measurements, but they merely give us glimpses into climates of the recent past. In order to look further into the past we have had to develop methods of interpreting climate data hidden within archives such as ice cores, tree rings, lake sediments, ocean sediments, soil carbonates and speleothems. The secret to inferring climate data from these records is in the establishment of transfer functions between climate and various proxies locked within the archive.
Some of the most heavily relied upon proxies within these records are the isotopes of precipitation. In Polar Regions, variability in isotopes of precipitation is considered to be dependant upon temperatures of condensation. At lower latitudes there is a host of climate parameters that can affect isotopic concentrations. These complications make for dubious interpretations of terrestrial isotope archives. Dependable interpretations can only occur when modern studies quantify concise and robust isotope/climate relationships.
This study used a new spatially and temporally dense network of precipitation collectors (USNIP) to articulate isotopic patterns in an understudied, mid-latitude region, the United States. We examined the effects of seasonality of precipitation on composite annual isotopic values, the influence of seasonally oscillating moisture source temperatures on seasonal isotopic patterns over land, and the climate parameters that cause isotopes to distribute as they do from one month to the next.
Indeed, we found that isotopes do vary significantly with temperatures of condensation; however, in some locations, the changing seasonality of precipitation within the U.S. likely has a greater effect on interannual isotopic patterns. Additionally, disparities between the observed and Rayleigh Model isotope-temperature relationships can be largely explained by varying moisture source temperatures. This study has brought clarity to many isotope/climate questions as well as introduced a dataset that can be used to raise and answer future questions.