HR: 1340h
AN: PP23A-1071    [Abstracts]
TI: Regional Reconstruction of Fire and Climate in Western Mongolia During the Past 1000 Years: Multi-Proxy Analysis of Sediments From Nine Lakes.
AU: * Umbanhowar, C E
EM: ceumb@stolaf.edu
AF: Saint Olaf College, 1520 St. Olaf Ave, Northfield, MN 55057, United States
AU: Johnson, L
EM: elizabeth.rose.johnson@gmail.com
AF: Saint Olaf College, 1520 St. Olaf Ave, Northfield, MN 55057, United States
AU: Gundsambuu, T
EM: gtseren@yahoo.com
AF: Institute of Botany Mongolian Academy of Sciences, 210351, Ulaanbaatar, 210351, Mongolia
AU: Lor, P
EM: lorp@stolaf.edu
AF: Saint Olaf College, 1520 St. Olaf Ave, Northfield, MN 55057, United States
AU: Nail, K
EM: nail@stolaf.edu
AF: Saint Olaf College, 1520 St. Olaf Ave, Northfield, MN 55057, United States
AU: Cook Shinneman, A
EM: averyshinneman@gmail.com
AF: St. Croix Watershed Research Station, Science Museum of Minnesota, 16910 152nd St. N, Marine on St. Croix, MN 55047, United States
AB: Northwestern Mongolia is an arid region of great climatic transition situated at the boundary between Siberian sub-arctic habitats, and the monsoon affected deserts of the south. Mongolia is among the high-elevation mid- latitude zones affected most strongly by modern climate change, however, there are relatively few records documenting either temporal or spatial patterns in climate or fire in this region for the past 1000 years. We conducted a multi-proxy (charcoal, LOI, IRM and ARM/IRM, P, diatoms and bSi) analysis of dated (lead-210 and AMS-Carbon) short cores (1-2m) of sediment from nine lakes along an ~ 550 km E-W transect in order to establish a regional history of climate and landscape change. Charcoal and other proxies showed considerable site to site and temporal variation likely reflecting regional heterogeneity in climate, lake-specific differences in source materials and runoff and diagenesis. Charcoal influxes were generally higher during the period 1200-1600 cal yr AD than 1600-2000 cal yr AD for 5 of 9 locations suggesting a shift to drier and/or cooler conditions, a conclusion which is underscored by a roughly synchronous decrease in the flux of bSi dating to ~ 1500 cal yr AD. IRM also shifts around 1500 AD, increasing at 6 of 9 sites and dropping at the remaining three sites. Recent years have seen major change, and charcoal at 8 of 9 sites dropped to virtually zero after 1850 cal AD while IRM, sediment-P, bSi flux all rose, coincident with increases in epilimnetic phosphorus from diatom-based reconstructions. Our data suggest that increased erosion and heightened nutrient loading to the lakes during the 20{th} century may be the combined product of drought and increased grazing intensity. Marked differences in proxy responses within and among our lakes highlight the need for climate reconstructions to be based on multiple sites and multiple proxies and to account for land use in combination with abiotic climate factors when examining changes to the landscape.
DE: 1512 Environmental magnetism
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1834 Human impacts
DE: 9320 Asia
DE: 9345 Large bodies of water (e.g., lakes and inland seas) (0746)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting