A longer vernal window: the role of winter coldness and snowpack in driving spring transitions and lags.
Climate change is altering the timing and duration of the vernal window, a period that marks the end of winter and the start of the growing season when rapid transitions in ecosystem energy, water, nutrient, and carbon dynamics take place. Research on this period typically captures only a portion of the ecosystem in transition and focuses largely on the dates by which the system wakes up. Previous work has not addressed lags between transitions that represent delays in energy, water, nutrient, and carbon flows. The objectives of this study were to establish the sequence of physical and biogeochemical transitions and lags during the vernal window period and to understand how climate change may alter them. We synthesized observations from a statewide sensor network in New Hampshire, USA, that concurrently monitored climate, snow, soils, and streams over a three-year period and supplemented these observations with climate reanalysis data, snow data assimilation model output, and satellite spectral data. We found that some of the transitions that occurred within the vernal window were sequential, with air temperatures warming prior to snow melt, which preceded forest canopy closure. Other transitions were simultaneous with one another and had zero-length lags, such as snowpack disappearance, rapid soil warming, and peak stream discharge. We modeled lags as a function of both winter coldness and snow depth, both of which are expected to decline with climate change. Warmer winters with less snow resulted in longer lags and a more protracted vernal window. This lengthening of individual lags and of the entire vernal window carries important consequences for the thermodynamics and biogeochemistry of ecosystems, both during the winter-to-spring transition and throughout the rest of the year.
Earth Systems Research Center, Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, NH, USA.
Alexandra R
AR
Contosta
Thayer School of Engineering, Dartmouth College, Hanover, NH, USA.
Alden
A
Adolph
Department of Environmental Studies, Keene State College, Keene, NH, USA.
Denise
D
Burchsted
Earth Systems Research Center, Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, NH, USA.|National Center for Atmospheric Research, Boulder, CO, USA.
Elizabeth
E
Burakowski
Center for the Environment, Plymouth State University, Plymouth, NH, USA.|United States Forest Service Northern Research Station, Plymouth, NH, USA.
Mark
M
Green
Physics Department, Saint Anselm College, Manchester, NH, USA.
David
D
Guerra
Thayer School of Engineering, Dartmouth College, Hanover, NH, USA.
Mary
M
Albert
Earth Systems Research Center, Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, NH, USA.
Jack
J
Dibb
Earth Systems Research Center, Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, NH, USA.
Mary
M
Martin
Department of Natural Resources and the Environment, University of New Hampshire, Durham, NH, USA.
William H
WH
McDowell
Earth Systems Research Center, Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, NH, USA.
Michael
M
Routhier
Earth Systems Research Center, Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, NH, USA.
Cameron
C
Wake
Environmental Science, White Mountain Community College, Berlin, NH, USA.
Rachel
R
Whitaker
Department of Natural Resources and the Environment, University of New Hampshire, Durham, NH, USA.|Water Systems Analysis Group, Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, NH, USA.
Wilfred
W
Wollheim
D057231:Climate Change; D017753:Ecosystem; D009513:New Hampshire; D012621:Seasons; D012914:Snow; D013696:Temperature
climate change; energy balance; lag; snow; soil; spring; stream; temperature; transition