WINTER PROCESSES ON A NEW ENGLAND MARSH: IMPLICATIONS FOR WETLANDS SURVIVAL IN A REGIME OF RISING SEA LEVEL

The back barrier marshes of New England form a unique ecosystem that is threatened by projected increases in the rate of sea level rise (SLR). Salt marshes maintain their elevation relative to rising sea level by means of vertical accretion, a function of inorganic sediment influx and organic sediment production. Salt marsh response to SLR has been extensively studied along the southeastern and gulf coasts of America, but less attention has been paid to northern marshes. These marshes experience different climatic conditions and do not appear to follow the model developed for southern inundation. Winter processes can play a significant role in the vertical accretion of the marsh surface through the process of ice rafting of sediment. Greater volumes of snow and ice on the marsh surface, however, may compress peat, leading to shallow compaction and a net loss of elevation in some areas. In addition, should New England marshes fail to keep up with rising sea level, their morphology may result in a different mode of inundation compared to southern back barrier marshes. Preliminary data indicate that ice rafting contributes a significant volume of sediment to the marsh surface (equivalent to a 0.325 mm-thick layer each winter), but results are inconclusive regarding the role of ice loading, and future work is planned.