Categorization of High-Wind Events and Their Contribution to the
Seasonal Breakdown of Stratification on the Southern New England Shelf
Abstract
High-wind events predominantly cause the rapid breakdown of seasonal
stratification on the continental shelf. Although previous studies have
shown how coastal stratification depends on local wind-forcing
characteristics, the locally observed ocean forcing has not yet been
linked to regional atmospheric weather patterns that determine the local
wind characteristics. Establishing such a connection is a necessary
first step towards examining how an altered atmospheric forcing due to
climate change affects coastal ocean conditions. Here, we propose a
categorization scheme for high-wind events that links atmospheric
forcing patterns with changes in stratification. We apply the scheme to
the Southern New England shelf utilizing observations from the Ocean
Observatories Initiative Coastal Pioneer Array (2015-2022). Impactful
wind forcing patterns occur predominantly during early fall, have strong
downwelling-favorable winds, and are primarily of two types: i) Cyclonic
storms that propagate south of the continental shelf causing strong
anticyclonically rotating winds, and ii) persistent large-scale
high-pressure systems over eastern Canada causing steady north-easterly
winds. These patterns are associated with opposite temperature and
salinity contributions to destratification, implying differences in the
dominant processes driving ocean mixing. Cyclonic storms are associated
with the strongest local wind energy input and drive mechanical mixing
and surface cooling. In contrast, steady downwelling-favorable winds
from high-pressure systems likely advect salty and less buoyant Slope
Water onto the shelf. The high-wind event categorization scheme allows a
transition from solely focusing on local wind forcing to considering
realistic atmospheric weather patterns when investigating their impact
on stratification in the coastal ocean.