Seasonal snow cover is important for the health of Northeastern forest ecosystems, influencing everything from soil temperatures and nutrient cycling to groundwater recharge and wildlife habitat.
A newly published paper reports that warming winter temperatures and shifting precipitation patterns may be altering these once predictable snowpack dynamics.
“Long-term measurements of seasonal snowpacks indicate increases in mid-winter snowmelt and earlier snowpack disappearance in the northeastern U.S.” published in PLOS Climate on December 18, 2024 by Wilson et al. (2024) is an in-depth look at how these snow cover characteristics have changed over the last half-century at the Hubbard Brook Experimental Forest (HBEF) in New Hampshire.
A long-term analysis that shows not only are snowpacks shrinking and disappearing earlier in spring, but mid-winter snowmelt events are also increasing.
Authors analyzed fifty-six years of weekly snow water equivalent (SWE) measurements from three locations at HBEF.
Sites vary by elevation and aspect, allowing the team to capture a range of microclimates.
By pairing these detailed field measurements with nearby daily records of climate conditions: temperature, precipitation, dewpoint, and solar radiation, authors were able to determine which factors best explain changes in snowpack onset, maximum accumulation, and disappearance.
Their findings highlight notable trends. “We found that maximum snowpack size and snowpack duration are shrinking at all sites,” say the authors.
Snowpack duration declined at rates ranging from about four days per decade at the coldest site to nearly ten days per decade at the warmest, south-facing site.
While in past decades snowpacks would persist well into spring, they now tend to disappear earlier.
Changes in the timing of snowpack onset were not uniform across locations; only the warmest, south-facing area showed a notable delay in establishing a seasonal snowpack.
One might expect an increasing share of winter precipitation to fall as rain rather than snow due to warming conditions.
However, the authors report that only the warmest site showed a decline in the fraction of precipitation falling as snow over time. At the colder, north-facing sites, the proportion of snowfall remained steady despite their shrinking snowpacks.
A primary driver appears to be enhanced snowmelt before snowpacks reach their historical winter maxima.
“Weekly data indicated that mid-winter snowpack losses are increasing,” the authors explain.
This is happening even where direct climate indicators of thaw, such as above-freezing days, have not appreciably changed.
Research points findings showing that the snowpack is becoming more sensitive and losing mass more readily at historically similar conditions.
Ultimately, the study suggests that “warmer, more sensitive snowpacks” are responding to climate change in complex ways.
The decreases in snowpack maximum and earlier spring disappearance owe much to subtle increases in snowmelt events throughout the winter, rather than dramatic changes in precipitation.
This more frequent mid-winter melting can lead to earlier soil warming, altered nutrient cycling, and less available spring runoff—all with potential consequences for forest health, water resources, and local economies reliant on winter recreation.
As climate continues to warm, these long-term, high-resolution datasets from HBEF offer important insights. They show that, even before precipitation patterns change substantially, warming winters are already reshaping the snowpack and the ecological processes it underpins.
Read the paper by: Geoff Wilson, Mark Green, John Campbell, Alix Contosta, Nina Lany, Amey Bailey