Documenting Holocene Paleohydrology Using Multiproxy Lake Core Studies in the Yukon Territory, Canada
Lindsey Witthaus, Pitt, Honors College undergraduate thesis Aug 2003 - present
Lesleigh Anderson, UMass, masters 2000 and Ph.D. 2005 now at the USGS
Our research has two main goals: (1) produce high-resolution multiproxy records documenting changes in the regional P-E balance for the last 2000 years from laminated lakes and (2) expand southeastward the network of sites with paleohydrological data that have been studied to date in Alaska. We seek to test hypotheses concerning the causes of shifts in the precipitation-evaporation (P-E) balance during the late Pleistocene and Holocene in the upper reaches of the Yukon River watershed. We will use lake systems at both ends of the hydrologic spectrum: (1) closed basin lakes and (2) overflowing lakes with large positive water balances and high watershed to lake area ratios. Our past experience in the region has shown an integrated study of open and closed basin sites is necessary to obtain paleoclimate records for the last ca. 15 ka B.P. because there have been large changes in the P-E balance from the late Pleistocene to the present. Promising preliminary data from core transect studies on closed basin lakes suggests water-level fluctuations have occurred throughout their history ( >11.8 ka B.P.). 2H and 18O measurements on modern surface waters across the region illustrate two points: (1) the proposed closed basin sites are sensitive to changes in the P-E and (2) the open basins have lake water that plots on the Local Meteoric Water Line (LMWL) indicating the effects of evaporation are minimal. Previous work based on pollen studies provides a broad paleoclimatic picture for this period. However, significant paleoclimatic questions remain unanswered, and high-resolution (< century-scale) climate reconstructions have not been attempted.
This research has three key goals:
(1) To produce well-dated records of several climatically sensitive proxies at century-scale resolution, in order to identify regional patterns of P-E balance from ca.15 ka B.P. to present.
(2) To identify higher frequency hydrological fluctuations over the past 2000 years, using more detailed analyses of the same proxies at higher resolution (decadal-scale or better).
(3) To compare these results with findings from our ongoing research across the interior of Alaska and in the Brooks Range.