Response of shallow lakes and ponds to contemporary climate change in the Hudson Bay Lowland near Churchill, Manitoba (Invited)
Abstract
Ponds and shallow lakes are a ubiquitous feature of Arctic coastal plains. In Canada, they are particularly prevalent in the Hudson Bay Lowland and the Mackenzie River Delta region. Recent ground-based and remote sensing observations have shown a general decreasing trend in arctic lake/pond surface area over the past 50 years, suggesting that small water bodies at high latitudes are drying. However, the majority of the work that has been done on drying ponds and shallow lakes (with the exceptional cases of increases in areal extent in a few regions found in the continuous permafrost zone) has been conducted in Alaska and Siberia. The objectives of this work are twofold: (1) to examine trends and seasonal variability in pond and shallow lake water levels and surface area during the open water season; and (2) to examine trends and variability in the duration of ice cover in ponds and shallow lakes in this region, as open water season evaporation totals have been shown to be strongly influenced by ice cover duration. Preliminary results related to the first objective of this study reveal that annual precipitation (primarily summer rainfall) and evaporation have increased between 1955 and 2008; however, rainfall appears to be increasing at a faster rate than evaporation. There is still a moisture deficit over the summer months in this region because evaporation exceeds precipitation, although this deficit appears to be lessening. Thus, conditions in this region appear to be becoming more wet. A change detection study conducted on a subset of ponds for four years using air photographs and a SPOT image show that pond surface areas appear to have fluctuated over the study period but do not show a consistent trend. Different pond sizes appear to be showing different trends. Small ponds are showing opposing trends to medium and large sized ponds and lakes. The behaviour of the small ponds appears to strongly reflect seasonality in pond-atmosphere hydrologic exchange, and observed changes in pond surface area are synchronous with “wet” periods and “dry” periods. Regarding trends and variability in ice cover duration, results from simulations of pond ice thickness, break-up and freeze-up dates, and duration of open water season over the period 1955-2008 suggest that temperatures are warming in this region, and that these changes are seen across winter, spring and summer. Correspondingly, break-up appears to be occurring earlier and freeze-up appears to be occurring later, leading to a prolonged ice-free season; though none of these trends are statistically significant over the past 54 years. Radar images taken over the past 14 years are currently being processed to examine temporal changes and spatial patterns in pond/lake ice cover across the study area. Results from this analysis will also be presented. Finally, the approaches developed in this study could form the basis of a general methodology for investigating the contemporary status of ponds and shallow lakes in the Arctic.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.C42A..03D
- Keywords:
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- 0746 CRYOSPHERE / Lakes;
- 1840 HYDROLOGY / Hydrometeorology;
- 1847 HYDROLOGY / Modeling;
- 6969 RADIO SCIENCE / Remote sensing