Departures of 1996 Temperatures and Salinities in the Middle Atlantic Bight and Gulf of Maine from Historical Means

Abstract
Monthly monitoring of surface and water column temperature, and surface salinity across the Middle Atlantic Bight and Gulf of Maine has been conducted since 1976 and 1978, respectively. Presented are the temporal and spatial patterns of these features in 1996 and their comparisons to mean patterns for the base period, 1978-92. Middle Atlan- tic Bight surface and bottom temperatures and surface salinities during 1996 were the lowest since the beginning of the base period. Annual, 1996, averaged surface tempera- ture over the entire transect was 1.9°C lower than the base period mean; similarly aver- aged bottom temperature was -0.8°C cooler; and like averaged surface salinities was 1.17 PSU below that of the base period. In the more detailed time-space sense, Middle Atlantic Bight temperatures were significantly lower than average 1) over the mid- to outer shelf from February through April, 2) over the shelf and slope during July and August, 3) over the mid-shelf in October, and 4) well offshore in November. Negative departures of sur- face salinity occurred over the shelf throughout 1996 and after July over the entire transect reaching the Gulf Stream. Bottom temperatures were significantly below average on the mid-shelf during January, expanding inshore by April. Negative departures occurred over the outer shelf area during the early summer, and continued through most of the remainder of 1996. In the Gulf of Maine, annual, 1996 averaged surface temperature along the entire transect was 1.1°C below the baseline, and similarly averaged bottom temperature was 0.2°C above the mean. In the time-space sense, Gulf of Maine surface temperatures were significantly below the baseline from January through March in Massachusetts Bay, ex- tending eastward to Crowell Basin in March. At this same time surface temperatures were as much as 4°C above average on the Scotian Shelf. From early July through September colder than average temperatures existed across the entire transect. Bottom temperatures were cooler than normal during January in Massachusetts Bay and in June through De- cember on the Scotian Shelf. Starting in January over the central Gulf ledges warmer than average bottom temperatures were observed. Significant positive anomalies reached the Scotian Shelf in February, Massachusetts Bay by March and continued in the mid-Gulf until July.

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