Lake Level Changes Under a Constant Climate
Abstract
Lake-level changes are important indicators of climate change, providing particular insight into the nature of hydrological balances (e.g., Benson et al., 1989; Cross et al., 2000). Indeed, evidence from paleo lake changes is one of the primary reasons the hydrological cycle in the subtropics have come to be seen as potential 'tipping points' of the climate system (Lenton et al., 2007). Our understanding of future lake-level variations is contingent on a more sophisticated understanding of the drivers of past lake-level variations. Two fundamental properties of geophysical systems are that there exists both some source of inertia (or 'memory'), and also a stochastic climate forcing - natural year-to-year fluctuations in climate. The effect of the inertia is to integrate the short time-scale variability and produce persistent anomalies on longer timescales, even in a constant climate (e.g., Hasselman, 1975; Wunsch, 1999; Roe, 2008). It is in the context of this natural variability that climate change must be evaluated. In the case of a lake, the volume of water plays the role of the inertia, and the random stochastic forcing is due to interannual variations in evaporation and precipitation. We have developed a simple, versatile lake-level model based on mass conservation, catchment area, surface evaporation, and lake-reservoir geometry, from which one can determine the dynamic response time of a lake. The model predicts lake-level changes in response to climate changes, and lake-level variability in response to stochastic, natural climate variability. The results clearly show that large and persistent lake- level anomalies can arise from stochastic climatic variability, even in the absence of a trend. In addition, we use this model to characterize the long-term variability of lake levels from threshold crossing statistics in order to determine (1) the lake-level variability expected from stochastic climate variability, (2) the rapidity and magnitude of lake-level changes required to be considered outside of that expected from stochastic variability, and (3) the length of the lake-level record necessary to be able to confidently attribute a trend in lake level to a trend in climate.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFMPP43B1532R
- Keywords:
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- 0746 Lakes (9345);
- 1616 Climate variability (1635;
- 3305;
- 3309;
- 4215;
- 4513);
- 1637 Regional climate change;
- 1836 Hydrological cycles and budgets (1218;
- 1655);
- 3344 Paleoclimatology (0473;
- 4900)