2003 Seattle Annual Meeting (November 2–5, 2003)

Paper No. 12
Presentation Time: 11:10 AM

CLIMATE, HYDROLOGY, AND PROXY RECORDS OF CLIMATE


CLOTTS, Rebecca, Geology and Geophysics, and Limnological Research Center, Univ of Minnesota, 310 Pillsbury Dr SE, Minneapolis, MN 55455, ITO, Emi, Limnological Research Center, Univ of Minnesota, 310 Pillsbury Drive, SE, Minneapolis, MN 55455, FORESTER, R.M., U.S. Geol Survey, MS 980 Federal Center, Denver, CO 80225, LEAF, Andrew, Geology Department, Gustavus Adolphus College, Nobel Hall of Science, St Peter, MN, ROSENBERRY, Donald O., U.S. Geol Survey, MS 413, Bldg. 53, DFC, Lakewood, CO 80225 and WINTER, Thomas C., U.S. Geol Survey, Mail Stop 413 Denver Federal Center, Lakewood, CO 80225, kemp0121@umn.edu

In order to investigate how lake and wetland hydrologic processes act as filters of climate signals recorded in sediments, we have been monitoring two nearly identical wetlands in close proximity (< 50 m). Both wetlands reside under the same climate, terrain, and the bulk of their water is received from snowmelt and spring rains, but they have different interactions with the groundwater.  One wetland (P8) currently functions as a through-flow basin; recharging and discharging the groundwater on opposite ends.  The second wetland (P1) receives a small amount of groundwater and primarily loses water through evaporation and secondarily to groundwater. P1 and P8 exhibit different water d18O, DIC d13C, and ostracode species assemblages. The d18O and DIC d13C are higher for P1 (d18O -3.5‰ vs -6.1‰ for P8, DIC d13C -4.6‰ vs -9.6‰ for P8) because of the longer residence time and the cumulative effect of photosynthetic activity. Ostracodes are small invertebrates sensitive to temperature, alkalinity/Ca ratio, and physical hydrology. Species such as Cypridopsis vidua and Potamocypris unicaudata are common to both P1 and P8, but Candona decora, Candona distincta and Notrodromas monicha, the species that prefer groundwater discharge sites, are only found abundantly in P8.  Thus even in these small wetlands with their simple hydrology relative to larger systems, hydrologic processes are modifying the climate signal as measured by proxies such as ostracode shell d18O and species assemblage before they are stored in the sediment. Such modification may not be easily discernible in a sedimentary paleoclimate record.