| Climate transportation effects on the Great Lakes hydrological cycle - :10970 | Office of Oceanic and Atmospheric Research (OAR)
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Climate transportation effects on the Great Lakes hydrological cycle
  • Published Date:
    1996
Filetype[PDF - 1004.86 KB]


Details:
  • Corporate Authors:
    Great Lakes Environmental Research Laboratory
  • Description:
    Historical climate scenarios, based on 41-yr data periods from the southeastern and southwestern continental United States, were used in hydrological models of the Great Lakes to examine possible changes in variability associated with various hydrological conditions. The Great Lakes Environmental Research Laboratory (GLERL) used their conceptual models for simulating moisture storages in, and runoff from, the 121 watersheds draining into the Laurentian Great Lakes, over-lake precipitation into each lake, and the heat storages in, and evaporation from, each lake. GLERL combined these components as net water supplies for each lake and estimated lake levels and connecting channel flows to consider transposed climate scenarios. We transposed four climate zones, ranging from 6° south and 0° west to 10° south and 11° west of the Great Lakes, to the Great Lakes area. These represent analog climates that could occur over the Great Lakes basin under global warming. This transposition of actual climates was essential since it incorporates natural changes in variability within the existing climate; this is not true for GCM-generated corrections applied to existing historical data in many other hydrological impact assessment studies. Average air temperatures increased between 4 and 11°C, and precipitation ranged from 80% to +170% of the current climate, over various lakes under various scenarios. These resulted in Great Lakes whole-basin water supply changes from the current condition of - 1% to - 54%. The higher air temperatures under the transposed climate scenarios led to higher over-land evapotranspiration and lower runoff to the lakes with earlier runoff peaks, since snowpack is reduced up to 100%, and the snow season is eliminated in some scenarios. This also resulted in a reduction in available soil moisture. Water temperatures increased and peaked earlier; heat resident in the deep lakes increased throughout the year. Mixing of the water column diminished, as most of the lakes become mostly monomictic, and lake evaporation increased. Water supplies decreased dramatically for the two driest scenarios with Lake Superior becoming a terminal lake. Also, lake level variability increased for all lakes for most of the scenarios. Maximum lake levels exceeded the recorded maximums for several scenarios on the lower lakes.

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