GIS for Paleo-limnological Studies

Abstract

Endorheic lakes, which are closed to hydrologic outflows, are extensively distributed in arid and semi-arid regions and are also vulnerable to climate change and human activities. Knowledge about paleo-environmental conditions is essential to our understanding of these current and ongoing changes. While contemporary lake dynamics are actively being monitored using various remote sensing data, paleo-lake changes are much more difficult to ascertain. Many lakes in endorheic basins are often found surrounded by paleo-shore relicts, attesting to a substantially different high water stand in the past. Paleo-lake inundation area retrieval and the subsequent lake volume change estimation are critical for us to understand the paleo-climatic and paleo-hydrologic environmental conditions. Geographic information systems (GISs) provide a powerful tool for analyzing these paleo-environmental conditions for lakes. This article summarizes GIS applications in paleo-limnological studies, introduces a semi-automated toolbox for regional-scale paleo-lake extent retrieval using geospatial information technologies, and models the lithospheric rebound caused by hydrologic unloading due to paleo-lake shrinkage. Paleo-shore relicts are first identified in high-resolution imagery, and their elevations are determined from digital elevation data. The paleo-lake extent automatically recovered by tracing the contour at the determined paleo-shore elevation and the water volume changes derived from the differences between the modern-day lake extent and the paleo-lake extent are then computed. We consider the recovered estimated lake volume changes to be conservative due to the effect of isostatic lithospheric rebound owing to the water mass loss. The lithospheric rebound as caused by the paleo-lake water unloading and the subsequent estimated lake volume losses acquired from the recovered paleo-lake extents is quantified by utilizing a spherically symmetric, non-rotating, elastic, and isotropic Earth model. The paleo-lake extent recovery toolbox is capable of reconstructing hundreds of paleo-lakes across the Tibetan Plateau at the regional scale, and this technique is broadly applicable toward the mapping of paleo-lake extents for endorheic basins in other arid and semi-arid regions around the world.