Sustaining Forests

Pilot Study

The Ice Storm Experiment has its roots in what appears to be the first-ever controlled, experimental ice storm manipulation in a forest ecosystem in February 2011. Water was pumped out of Hubbard Brook and sprayed over the forest canopy during subfreezing conditions to simulate a glaze ice event. The falling water froze on contact, resulting in 0.4 inch of ice accumulation, which is comparable to measurements at Hubbard Brook during the major ice storm of 1998 that affected much of the northeastern United States and Canada. This initial experiment provided proof of concept that a controlled ice storm experiment could be done, and evaluated forest damage and effects on carbon sequestration.

Read more:

Rustad, Lindsey E.; Campbell, John L. 2012. A novel ice storm manipulation experiment in a northern hardwood forest. Canadian Journal of Forest Research. 42: 1810-1818.

Featured Resources

Ice Storm Experiment

Research Issue

[photo:] Researcher studies effects of icing on trees in Hubbard Brook Experimental Forest. Photo by Joe Klementovich, Hubbard Brook Research Foundation.Ice storms are an important natural disturbance in forest ecosystems of the “ice belt” that covers a broad area extending from east Texas to New England. These glazing events (defined as one-quarter inch of ice accretion or more) are often perceived as rare occurrences, even though the return interval is as short as 2-5 years in the most ice storm prone northeastern U.S. Ice storms are major causes of forest disturbance in north temperate and boreal forest ecosystems worldwide.

Despite the influential role of ice storms in shaping forest ecosystems, knowledge of ice storms and their impacts remains limited, largely because these storms are hard to predict in time and space, and scientists don’t know when or where they will next occur.  When they do occur, scientists are not often prepared with careful pre-ice storm data or able to mobilize a research program to study response. Thus, rather than becoming “ice storm chasers”, researchers at the Hubbard Brook Experimental Forest, in the White Mountain National Forest of New Hampshire, brought the ice storms to their own extensive “outdoor laboratory.” In the first ever controlled study of ice storms, scientists are using a suite of tools, including creating artificial ice storms, to study the impacts of these storms on northern hardwood forests.  This research will provide the scientific community, land managers and the concerned public greater insight on the impacts of these powerful, frightening, and curiously aesthetic extreme winter weather events on ecosystem dynamics in northern hardwood forests.

Our Research

The Hubbard Brook “Ice Storm Experiment,”, is funded by a grant from the National Science Foundation (DEB-1457675 - Collaborative Research: Understanding the Impacts of Ice Storms on Forest Ecosystems of the Northeastern United States). The Ice Storm Experiment is an integrated program of research built on an impressive foundation of previous work at the site and by the research team, including:

bulleted itemA pilot ice storm experiment conducted at the Hubbard Brook Experimental Forest in 2012; 
bulleted itema significant body of research on the response of the Hubbard Brook Experimental Forest and surrounding regional forests to the severe "Ice Storm of 1998"; and
bulleted itema new set of historical climate reconstructions that allow for the quantification of meteorological conditions consistent with ice storms.

Research team sprays fine mist on forested area during artificial ice storm experiment.The team set up 10 plots, each 20 x 30-m, or about the size of a basketball court. Ice was applied to replicated plots in increments of one-quarter-inch, one-half-inch, and three-quarters of an inch in the winter of 2016. Two plots that received one-half inch of ice in 2016 also received a second one-half inch of ice in January of 2017 to simulate what might happen to the forest if major ice storms occurred in back to back years. For perspective, the National Weather Service issues an ice storm warning in southern New England for storms producing one-quarter-inch of ice, and issues an ice storm warning in northern New England for storms producing one-half-inch of ice or more.

Ice storms had to be created under specific weather conditions. The weather prior to icing had to be below freezing for several days to create frozen surfaces; the weather day of icing had to be below 20oF to create proper conditions for sprayed water to freeze on contact on cold surfaces; and the weather for a day or two after icing had to be below freezing so the ice would remain on the trees for several days and not immediately melt off. Icing during cloudy days was preferable to sunny days because trees act like giant solar collectors, again melting ice rapidly. Weather conditions allowed for icing on three sets of dates in January and February of 2016 for the first year of icing, and on January 13th through 17th, 2017 for the second year of icing. To apply the ice, icing crews (including sprayers, hose tenders, mechanics, UTV drivers, ice measurers, EMTs, and helpers of all kinds) set off for the plots by snow mobile at dusk, to ice at night which is the coldest time of the day. The ice crews worked all night, finishing their icing and measurements at dawn. To ice, they maneuvered all-terrain vehicles equipped with fire hoses along the sides of the plots, spraying water from the main branch of the Hubbard Brook up and through gaps in the canopy so it would descend on the forest as a fine mist, and freeze on branches and tree boles on contact.  It took two to four hours to ice a single plot. The prolonged exposure to the cold required the scientists to consider safety first and science second: they had three EMTs available on site, rescue sleds in place, as well as a heated warming tent complete with hot chocolate, soups and stews to allow icers to have dry and comfortable respite from the elements.

National Science Foundation Video on Ice Storm Experiment

Expected Outcomes

This research will provide the scientific community, land managers and the public with greater insight on the impacts of these powerful, frightening, and curiously aesthetic extreme winter weather events on ecosystem dynamics in northern hardwood forests.

Specifically, the research is expected to result in:
bulleted item Development of high-resolution global climate model simulations to evaluate future severity, frequency and extent of ice storms;
bulleted item Evaluation of short-term (2-3 year) ecosystem response to four different intensities and two frequencies of experimental ice events;
bulleted item Evaluation of longer-term (18-plus years) responses of forest vegetation to the 1998 storm;
bulleted item Improvement of an established forest ecosystem biogeochemical model based on results from the experiment and the long-term observations;
bulleted item Ability to project future ice storm impacts on ecosystem fluxes and pools of carbon and nitrogen in a northern hardwood forest.

In addition, the Ice Storm Experiment will be integrated with broader impacts involving a program to use sensor technology to engage STEM students with disabilities in the study; a dialog of the impacts of ice storms with local stakeholders; the production of a video on the making of an ice storm and relevance to extreme events and climate change, and undergraduate, graduate and post-doctoral training.


Early Observations

Early results from the 2016 icing show dramatic response to the range of icing, with the amount of coarse woody material (branches and tree stems over about an inch in diameter) and fine woody material (twigs less than about an inch in diameter) that came down in the simulated storm being roughly proportional to the amount of ice applied. Scientists also learned that the amount of fine woody material that came down after a single half inch ice storm was about equal to what comes down during the entire year in a normal year. The amount of big debris downed in a single half inch storm was an order of magnitude greater than that of the typical year. Such findings become useful for cleanup and salvage cutting efforts.

Research Participants

Principal Investigators

Research Partners


Last Modified: March 24, 2017