Description of the 2012 Oceanographic Conditions on the Northeast U.S. Continental Shelf

Hydrographic observations from twelve surveys spanning the Northeast U.S. Continental Shelf are combined into a descriptive overview of the broad-scale oceanographic conditions that were observed during 2012. Temperature and salinity observations are combined into six 2-month time periods in order to maximize both the spatial coverage of the data and its temporal resolution during the year. Maps of near-surface and near-bottom property distributions are presented for each bi-monthly period and time series of regional average properties are discussed for five geographic regions spanning the shelf: western Gulf of Maine, eastern Gulf of Maine, Georges Bank, and northern and southern Middle-Atlantic Bight. The entire Northeast U.S. Continental Shelf was warm in 2012 relative to the reference period (1977-1987), with warm conditions penetrating to the bottom over much of the region. Warming was greatest during the late winter in the southern Middle Atlantic Bight, peaking during summer elsewhere. Bottom waters in the Middle Atlantic Bight Cold Pool were warmer and this feature was slower to erode in the fall, perhaps due to enhanced stratification brought on by warmer surface conditions in the preceding spring/summer. Conditions in the Gulf of Maine were also warm, driven by atmospheric heating at the surface and by the advection of a warmer/saltier variety of slope water mass at depth. Like the Cold Pool in the Middle Atlantic Bight, the Cold Intermediate Layer in the Gulf of Maine was warmer during the spring of 2012, presumably a consequence of a less developed and warmer winter mixed layer during the preceding winter.