Quick Summary
- Scientists placed a network of sensors in remote mountain lakes to learn how the lakes spend their winter
- Study is the first to look at ice cover and under-ice conditions in small Sierra Nevada lakes
How small mountain lakes spend their winters is largely unknown to scientists, despite winter representing nearly half the year in such environments. A study by the 色中色, helps demystify what happens above and below the ice.
, published in a of the Journal of Geophysical Research: Biogeosciences, is the first to look at ice cover and under-ice conditions in small Sierra Nevada lakes, which number in the thousands.
Such baseline knowledge is critical for understanding how high-elevation lakes respond to climate change and to the loss of ice and snow. Despite heavy snowfall this winter, climate projections estimate the Sierra snowpack could drastically shrink or even disappear by 2100.
鈥淲inter is a big part of the year. We don鈥檛 understand it, and we鈥檙e losing it,鈥 said lead author Adrianne Smits, a National Science Foundation postdoctoral scholar at 色中色. 鈥淟akes in many cold regions of the world are losing ice cover fast, and very few studies examine what happens to them in winter. People assume they鈥檙e hibernating or dead, and the more we learn, we find that鈥檚 completely false.鈥
A sense of snow
For the study, researchers placed a network of underwater sensors in 15 remote mountain lakes throughout the Sierra Nevada to try to understand what type of lakes may be the most sensitive to loss of snow and ice cover. Placed during the more accessible warmer months, the sensors took hourly measurements of water temperature, dissolved oxygen, the timing of ice formation and breakup, and other climate variables for up to five winters.
The study found that most mountain lakes will have shorter ice cover, warmer water and higher oxygen concentrations as winters warm. But small and large lakes will respond differently to the loss of ice cover and snow, with small lakes being more susceptible to changes between wet and dry years.
Other findings include:
- Snowfall and air temperature determine when ice breaks up and how long it lasts.
- Lake size and shape control oxygen and temperature immediately after ice forms, but late winter conditions depend on other variables that dictate how long ice covers the lake.
- Small, shallow lakes experience low-oxygen conditions more so than large, deep lakes. However, shallow lakes are also more dynamic because heavy snowfall causes ice to submerge, changing oxygen levels as water is displaced by ice.
The findings can help inform conservation management related to water resources, endangered and threatened species, and summer algal blooms, which thrive in years with early ice breakup.