Three Decades of Subsurface Water Temperature Measurements Reveal Warming Trends and Deep Water Dynamics in Lake Michigan
Abstract
Lakes have been identified as sentinels of climate change due to their ability to integrate conditions across spatial and temporal scales while providing discernable signals of change in physical and biological indices. For instance, recent investigations have reported global lake surface water temperatures are warming at rates faster than ocean temperatures and regional air temperatures. However, most of Earth's surface freshwater resides in a just few of its largest lakes, and yet our understanding of how these lakes are responding to climate change is limited because few large lakes have long-term, high-frequency, and high resolution data at depth. Here we use a thirty-year record of nearly continuous hourly subsurface temperature measurements in Lake Michigan to understand the impacts of surface warming on deep water. We find warming trends in the fall, winter, and spring throughout the water column and the dynamics of how the subsurface responds to these changes. Delays in the fall turnover, associated with longer summer stratified periods, is shown to be the start of a cascade of subsurface impacts that include shorter winter cooling periods, higher minimum temperatures, earlier summer stratification, and higher stratification temperatures in the deep water. The relationships between delays in turnover and subsurface impacts highlight the pathway to mixing regime shift in a large dimictic lake. The impacts of bottom temperature shifts and warming will have a profound impact on the ecology and water quality of the world's largest lakes.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMH125...07A
- Keywords:
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- 3322 Land/atmosphere interactions;
- ATMOSPHERIC PROCESSES;
- 0458 Limnology;
- BIOGEOSCIENCES;
- 0466 Modeling;
- BIOGEOSCIENCES;
- 1807 Climate impacts;
- HYDROLOGY