Ascension : Ascension Island Conservation Department
Submitted by The Islander (Conservation Office) 18.10.2012 (Article Archived on 01.11.2012)

Ascension Island – a lonely piece of land in a seemingly borderless ocean turned out to be the centre of an oceanographic ‘collision’ which does not happen very often in featureless seas

Ascension Island Conservation Department

Oceanography studies-Contributed by Vladimir Laptikhovsky -Posted on September 8, 2012 by SMSG

Ascension Island – a lonely piece of land in a seemingly borderless ocean turned out to be the centre of an oceanographic ‘collision’ which does not happen very often in featureless seas. Here, the central branch of the Southern Equatorial Current that normally goes on surface meets the Southern Equatorial Counter-Current that normally goes in subsurface layers but right here, between 7 and 8°S, it travels to the surface. Interactions of these two streams give rise to high water turbulence, numerous gyres and eddies and other kinds of water unrest. Those, combined with upwelling areas in inshore waters caused by the bottom topography, are responsible to the high productivity of the area that attracts numerous large predators close to shore that might be seen filleted on Georgetown pier almost every night.

To study the local oceanographic features, a total of 16 oceanographic stations with manually deployed CTD (Conductivity – Temperature – Density) devices were carried out. To complete the picture around the island, Vlad Laptikhovsky, Steve Cartwright, Wetjens Dimmlich, Frithjof Kuepper and Kostas Konstantinos circumnavigated Ascension in the comfort of the Queen of Atlantis. Generally conditions in the voyage were good but did become quite rough along the more exposed coast near Boatswain Bird Island.

The results reveal a complicated oceanographic structure even in the upper 50-m layer, where waters of both the major oceanic currents combined with a mixed layer of local origin.

During the past two weeks the interaction of these currents was quite mobile. The cold productive Counter-Current eventually occupied the surface layer around most of the island, excluding the small offshore part in the north around English Bay. The more saline (because of evaporation) Equatorial Current moved its water mostly deeper than 20 m revealing expected phenomenon of temperature increase with depth, and surfaced only in the very north of the studied area.

Please be advised that due to on-going field work the Conservation Office will open from 7.30am -10am during week days. We open as normal on Saturdays, 10am-12noon, signs will be posted on the door when the office is closed. Sorry for any inconvenience this may cause. Volunteers welcome. Please contact Natasha Williams or Jolene Sim.  Ascension Island Conservation Department. Georgetown. Tel: 6359. Email:  natasha.williams@ascension.gov.ac  or jolene.sim@ascension.gov.ac