Role of wind in regulating phytoplankton blooms on the Mid-Atlantic Bight

摘要

Mixing has long been recognized as having an important role in influencing underwater light and nutrient budgets and thus regulating phytoplankton bloom. Mixing related to stratification and de-stratification is a key parameter of the physical environment that can control the timing and magnitude of blooms. Here we use a high-resolution three-dimensional biogeochemical model in the Mid-Atlantic Bight (MAB) to study phytoplankton bloom dynamics for the years 2004-2007. We present a simulated fall-winter bloom in the shelf region and spring bloom in the shelf-break front region. The ratio of light over mixed layer depth (MLD) was used to determine the trade-off effects of mixing (increase mixing will increase nutrients availability but decrease light availability). We find that the critical light value (I'_(chl mas)) is around 60 (Wm~(-2)) for the shelf region and 150 (Wm~(-2)) for the shelf-break front region. There is a predictable linear regression relationship between I'chl mas and depth. A sensitivity run with no wind forcing was used to test the role of wind-induced mixing on the balance between light and nutrient terms and its influence on timing and magnitude of the bloom. The phytoplankton dynamics in the shelf-break front region are found to be more sensitive to the wind-induced mixing.