Published February 11, 2025
By Meredith Journey
This blog post is adapted from a presentation held in December 2024
“My name is Meredith Journey, and I am a PhD student with Annika Walters, working on Alpine lake ecology. I am looking at shifting snow and ice phenology and its downstream effects.
Snowpack, particular in the Wind River range, is very important to the water supply in Wyoming. The source of the Upper Green River, for example, is an Alpine lake in the Wind River range. In the early 2000s, the Wind River range snowpack was already melting about two weeks earlier than historically.
Lakes are sentinels for climate change. Wyoming Alpine lakes house a valuable recreational fishery to the state, and increased productivity or longer ice-free seasons could lead to harmful cyanobacteria blooms. Glaciers are also important. Most of the active glaciers in Wyoming are in the Wind River range, and increased sediment input is expected with glacial recession.
Let’s look at how snow and climate are impacting the lake ecology, which is then impacting the ecosystem function.
We have predictions for snow and climate, but we don't have predictions for the other two. If we link everything, we can predict changes, delayed ecology and ecosystem function. Climate, snow and temperature are drivers, and then we're looking at both indicators and outcomes. Indicators being primary productivity, or chlorophyll and phytoplankton, and secondary productivity, zooplankton. The final outcome is trout productivity. We have nutrients involved in all of this, and we're adding glacial recession to it.
The first part is linking climate and snow back to lake processes. We have four types of data:
When snow goes down in the early part of the season, the lake temperature hangs around 1-2°C. Right as the snow goes to zero, we're hitting an important process called spring turnover, where temperature stays at about 4°C for about a week.
In our research, we relate snow water equivalent (SWE) and day of year. The date of SWE = 0 and the date of ice off are closely related to each other, differing somewhat between early and late melt onsets. So far, it looks like snow is driving the onset of spring turnover in these lakes.
But we can do more with these data. We can see the ice over period when the temperature is consistent and the transition period into spring turnover. The other important part is the duration and the change during the summer stratification period, which is also the growing season or generally the ice-free season.
Temperature and chlorophyll across the 2024 season were collected once a month from a raft in the middle of the lake. You can think of chlorophyll as productivity. There is a change over the season for productivity based around the early season. We have a mixing period where there's chlorophyll in the whole water column, and then there's a stratification of that chlorophyll that coincides with the temperature stratification in the lake. We are starting to link some of the biological season back to the snow, not just the physical metrics.
2024 was our pilot season for some glacial or sediment heavy lakes. Essentially, we found that these glacial lakes lack a thermocline. The water is heavier on top because of the high sediment input, and this prevents stratification. They also have very low chlorophyll since there's not a lot of light penetrating through water. Nutrient and zooplankton sampling will be a focus of the field season for 2025.”
thermocline: the transition layer between warmer mixed water at the ocean's surface and cooler deep water below (NOAA)
