Airborne expendable bathythermograph surveys of the eastern Mediterranean

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Abstract
Two extensive airborne expendable bathythermograph (AXBT) surveys of the eastern Mediterranean were conducted during December 1991 and July 1992 from a Naval Oceanographic Office RP‐3 aircraft. Larger areas were sampled over shorter periods of time than is possible with conventional surveys carried out by ships. The circulation of the eastern Mediterranean consists of a collection of subgyres and fronts which show surprising seasonal and interannual variability. These surveys help to describe further this variability which is only partially understood. In particular, the surveys provide additional evidence that a relatively strong anticyclone located adjacent to the southeast corner of Crete during the late summer and through fall is a consequence of strong north winds from the Aegean, the Etesians, being blocked by Crete. Also notable in both surveys was the absence of “a” strong Mersa‐Matruh gyre, an anticyclone or anticyclonic subgyre off the Egyptian coast generally considered to be permanent. In contrast to published earlier observations, the Mersa Matruh gyre system was more a collection of weaker anticyclones rather than a single, sometimes double centered, strong feature. In both surveys we saw a string of anticyclones off the African coast between about 24° and 32°E. In general, these eddies did not exhibit a significant surface thermal structure, but were most evident in the 200 m to 300 m‐depth depictions. It may be that the formation of a strong southeast Crete anticyclone inhibits the formation of a large, relatively strong Mersa‐Matruh subgyre by interacting with the mid‐Mediterranean jet. If so, then both the southeast Crete anticyclone and the Mersa‐Matruh anticyclone could both be recurrent but tend to occur at different times.