Quantifying Snowpack Properties and Snow Impurity Dynamics Over Three Consecutive Winters in New Hampshire

Abstract:

Seasonal snowpacks accumulate impurities derived from atmospheric aerosols and trace gases throughout the winter and can release them quickly during a melt period, thus having an impact on the surrounding environment. The timing of the melt and the amount of impurities within the snowpack will affect how receiving ecosystems can manage the rapid release of these materials during a melt event. Previous field and laboratory studies have shown that a snowpack can lose up to 80% of its ions in the first 20% of the runoff, an event commonly known as an ionic pulse. On the other hand, some studies have found that particulate impurities (e.g. dust and black carbon (BC)) can be concentrated in surface layers during melt, darkening the snowpack. To characterize snow chemistry and quantify the rate of release of impurities during melt, we collected and analyzed near daily chemical profiles in the snowpack at three sites during three winters in New Hampshire, USA. Using the same datasets, we are also investigating the spatial variability of snow chemistry and the movement of impurities within the snowpack throughout the winter, with plans to use additional stream and soil datasets to investigate how any ionic pulse spreads into soils and nearby streams. Preliminary results suggest that an ionic pulse is occurring when New Hampshire’s snowpack melts, with at least 50% of some chemical inventories leaving in the first 21% of the melt. BC also tends to flush out of the snowpack more quickly than snow water equivalent decreases during melt, but slower than most ions. We also found that sodium and chloride ratios suggest that a large portion of these ions may be derived from nearby road salt application rather than sea salt, even at two sample sites located in New Hampshire’s coastal region where a signal from sea salt aerosol may be expected to dominate.