Upwelling along the western barrier reef of New Caledonia
Christian Hénin A and G. R. Cresswell B CA IRD Centre, Nouméa, New Caledonia, France.
B CSIRO Marine Research, Box 1538, Hobart, TAS 7001, Australia.
C Corresponding author. Email: george.cresswell@csiro.au
Marine and Freshwater Research 56(7) 1005-1010 https://doi.org/10.1071/MF04266
Submitted: 26 October 2004 Accepted: 20 June 2005 Published: 20 October 2005
Abstract
Temperature decreases of up to 5°C at an automatic station at ~10 m depth at the outer reef of western New Caledonia signalled the occurrence of upwelling. The decreases are related to south-easterly wind events and they can take up to 5 days to develop. Successive wind events can depress the temperature for as much as 1 month. An upwelling shows in thermal satellite imagery as a band of cold water ~10 km wide and as long as several hundred kilometres just outside the reef. The cold water frequently spreads out to sea. The upwellings are more common in summer (October to March) than in winter. During lengthy periods of low wind speeds, the waters outside the reef appear to be overrun by warm water from farther north. The frequent occurrence of the warm water layer in the north may partly explain why upwellings are more common along the southern half of the reef. The entire lagoon cools in winter; most of the lagoon warms in summer, except at the southern end where the waters are cool, perhaps from tidal mixing.
Extra keywords: satellite images, wind stress.
Acknowledgments
The automatic observations at the coastal stations around New Caledonia were funded, respectively, by CORDET and by ZoNéCo programmes. METEO-France provided the meteorological observations of Amédée lighthouse. The coastal station systems were installed and maintained by IRD and by the Aquarium de Nouméa’s professional divers Jean-Louis Menou, Georges Bargibant, Pierre Laboute, Pascal Hamel and Alain Gerbault and by the crew of the Dawa (Philippe Tirard, Georges Callejon, Raymond Proner). The systems were prepared by Luc Foucher and the data were managed by David Varillon. At CSIRO Jim Mansbridge handled much of the data and Chris Rathbone processed SeaWIFS satellite images.
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