Middle Atlantic Bight study area bathymetry (5 min TerrainBase). The shaded area shows extent of planview data. Boxes show New Jersey and Nantucket Shoals cross-shelf study areas.

The Middle Atlantic Bight (MAB) shelfbreak front separates the cool, fresh water of the continental shelf from the warm, saline water of the continental slope. A number of previous studies have quantified the mean structure and variability of the Middle Atlantic Bight shelfbreak front [Wright, 1976, Halliwell and Mooers, 1979, Naimie et al., 1994, Linder and Gawarkiewicz, 1998]. This study uses a new method to compute two-dimensional planview climatological fields of temperature and salinity from Georges Bank to Cape Hatteras.

Data Sources

•  Hydrobase2 climatology (collection of raw profile data from the World Ocean Database 1998 [Levitus et al. 1998], WOCE Hydrographic Programme, NSIDC (Joint U.S. / Russian Atlas of the Arctic Ocean), ICES, BarKode (Barents and Kara Seas Oceanographic Database) and various other sources obtained by personal communication with the PIs who collected the data.)
•  Shelf-Edge Exchange Processes (SEEP) hydrographic data
•  NOAA National Marine Fisheries (NMFS) hydrographic data from 1990-2001 (courtesy Maureen Taylor, NOAA).

Method - Planview

A regular grid is created in Lat/Lon space with 0.2 degree resolution. The program searches in a radius of 25 km from each grid point to find available profiles. Then, data points within each profile are selected based on a chosen depth range. In this project we are studying three key depth ranges: surface (5-15m), intermediate (40-55m), and shelfbreak (80-100m). The weighted mean and standard deviation are then computed for each grid point using a Hamming window filter, which gives more emphasis to data near the output grid point. Areas for which there is not sufficient data density are left blank (shown as white space on plots).

Plots - Planview

The following plots show the data density, mean & standard deviation of temperature, salinity, and density for the three depth ranges.

Observations - Planview

The above plots show the mean and standard deviation of various water properties of the MAB. The shelfbreak front divides cool, fresh shelf water from warm, salty slope water.

Method - Nantucket Shoals cross-shelf section

The Nantucket Shoals and New Jersey cross-shelf sections are an entirely separate product from the above planview climatology. They were created using a different method. In this version, the profiles (from only the bounding boxes shown above) are sorted based on their minimum (perpendicular) distance from the 100m isobath. The horizontal resolution is 10km (extending from 60km onshore to 40km offshore of the 100m isobath), and the vertical resolution is 10m. Thus, if a profile is determined to be 6 km shoreward of the 100m isobath, it is placed in the 0-10km shoreward bin. All data points in this profile from the surface to 10m are placed in the first vertical bin, then points between 10m and 20m are placed in the second vertical bin, etc. When all of the data points have been sorted, statistics (mean and standard deviation) are performed on the bins' temperature and salinity values. The 2D output mean fields are then smoothed using a bicubic spline. To further improve the robustness of our calculations, we have broken the time periods into seasonal bins. Spring is defined as any profiles collected in Apr/May/Jun, Summer is Jul/Aug/Sep, Fall is Oct/Nov/Dec, and Winter is Jan/Feb/Mar. As expected, data density is highest on the shelf and shelfbreak, and tapers off with distance offshore.

Plots - Nantucket Shoals and New Jersey cross-shelf sections

The following plots show the mean & standard deviation of temperature, salinity, and density. The color contour data is the mean, and the overlaid black line contours are the standard deviation.