Decadal Variability of Climate and Winter Phytoplankton Bloom in the Mid-Atlantic Bight

The inter-annual variability of winter phytoplankton bloom in the Mid-Atlantic Bight (MAB) is examined using a combination of satellite data and biogeochemical ROMS model for the time period of 1983-1986 and 2004-2008 during which two ocean color sensors provide data for the MAB. The MAB has been experiencing significant changes over the last 30 years, with warmer atmospheric and water temperatures, increased river discharge, and increased wind forcing in the fall-winter. Based on satellite and glider observations, the winter bloom magnitude is enhanced by increased water column stability. Given the counteracting effects of wind, temperature and river discharge we conducted a stability analysis for the two time periods, where the balance between mixing (tide and wind) and buoyancy (heat and freshwater) processes, are used to define winter mixing. Model simulations suggest that phytoplankton blooms have increased slightly in the winter despite the increased wind forcing. This suggests that enhanced river flow is playing a significant role in enhancing MAB winter phytoplankton despite increased wind forcing.