Lake Temperature Trends

NPS employees re-deploy a temperature array at Lake Clark National Park and Preserve. NPS/Paul Gabriel

We know from past studies that summertime surface water temperatures are warming in lakes, worldwide. Less well studied are changes in lake temperatures throughout the year and water column. Given that many fish–including juvenile salmon–experience more than just summertime surface water temperatures, a deeper understanding of lake temperature trends is warranted. In a recently published report, we used year-round, multi-depth data from moored installations known as temperature arrays to assess trends from 2006 through 2018 in four lakes with relatively easy access, heavy use, and focused concern for management. Although the temperature array dataset is relatively limited in both space and time, it encompasses more than 4 million records in a region where continuous water temperature data are generally lacking. Our findings indicate that:

monthly mean surface water temperatures have warmed at all arrays since monitoring began;

at some arrays, strong warming trends extend to deeper waters; and

the rate of warming varied from 0.02 to 0.24 °C per year, depending on the array and depth.

At the low end of this range, the rates are small, when considered on an annual timestep. However, if the rates persist, they may amount to ecologically significant changes over time, particularly in the surface waters where juvenile salmon feed. The optimal temperature range for juvenile salmon is 12-15 °C, with the upper end of this range marking the state’s water quality threshold for freshwater habitats that support fish rearing. It is noteworthy, then, that daily mean surface water temperatures have already exceeded the state’s threshold at some point during the period of record at all arrays, while deeper waters (below 20 m) have not. Collectively, this suggests that deeper waters may offer refuge to juvenile salmon–now and in the future–even when temperatures higher in the water column are suboptimal.

Where this belongs

• Katmai National Park & Preserve
• Lake Clark National Park & Preserve

Where this page came from

This page was imported from National Park Service. Produced by the U.S. National Park Service and, as a work of the United States government, in the public domain.

Nobody has written it yet — it is the source material at a new address, which is why search engines are asked to skip it and why no one earns from it. It is up for grabs: take it on, and it is yours to rewrite and to earn from.