Airborne expendable bathythermograph surveys of the eastern Mediterranean

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.

Cyclostrophic Corrections of AVISO/DUACS Surface Velocities and Its Application to Mesoscale Eddies in the Mediterranean Sea

“…Nevertheless, Mkhinini et al () have shown that the Herodotus Trough is a formation area of long‐lived anticyclones. These mesoscale anticyclones, often called Mersa‐Matruh eddies, have been mentioned in several studies (Amitai et al, ; Hamad et al, ; Horton et al, ; Menna et al, ) but never identified as intense eddies. The instabilities of the Libyo Egyptian Current or the local changes of the mean shelf slope could explain the formation of intense meanders or coastal anticyclones in this area.…”

Dynamical Evolution of Intense Ierapetra Eddies on a 22 Year Long Period

“…This intense and large‐scale anticyclone is generally formed during the summer months at the south‐east corner of Crete. The Ierapetra eddy (IE) was first identified from the POEM hydrographic data by Theocharis et al (), then, by Horton et al () based on two extensive airborne expendable bathythermograph (AXBT) surveys conducted during December 1991 and July 1992. Horton et al () and Fusco et al () suggested that this intense anticyclone is a consequence of the strong Etesian winds being blocked by the Cretan orography.…”

“…The Ierapetra eddy (IE) was first identified from the POEM hydrographic data by Theocharis et al (), then, by Horton et al () based on two extensive airborne expendable bathythermograph (AXBT) surveys conducted during December 1991 and July 1992. Horton et al () and Fusco et al () suggested that this intense anticyclone is a consequence of the strong Etesian winds being blocked by the Cretan orography. The seasonal correlation, averaged over 20 years, between the formation area of the IE and the localized area of negative wind stress curl seems to confirm this hypothesis Mkhinini et al ().…”

Near Real Time SLA and SST products during 2-years of MFS pilot project: processing, analysis of the variability and of the coupled patterns

“…The SST and the altimetric data have, for instance, considerably improved the knowledge of the sea surface variability. This is characterised by a complex combination of transient, seasonal and interannual signals (Matteoda and Glenn, 1996;Horton et al, 1994;Roether et al, 1996;Marullo et al, 1999a, b;Santoleri et al, 1994). The importance of the latter with respect to the others implies some difficulties to propose a stable seasonal scheme for the surface circulation.…”