Fiedler, Björn

Funk, Andreas

Kanzow, Torsten

Karstensen, Johannes

Krahmann, Gerd

Müller, Mario

Ohde, T.

English

OceanRep

Glider fleet-based, multi-parameter observations in the tropical Northeast Atlantic

Geophysical Research AbstractsVol. 13, EGU2011-9001, 2011EGU General Assembly 2011© Author(s) 2011Glider fleet-based, multi-parameter observations in the tropical NortheastAtlanticTorsten Kanzow (1), Gerd Krahmann (1), Johannes Karstensen (1), Thomas Ohde (2), Andreas Funk (1), andMario Müller (1)(1) Leibniz-Institut für Meereswissenschaften, Chrstian-Albrechts-Universität Kiel, Ozeanzirkulation und Klimadynamik,Kiel, Germany (tkanzow@ifm-geomar.de), (2) Leibniz-Institut für Ostseeforschung Warnemünde, Rostock, Germany(thomas.ohde@io-warnemuende.de)Mesoscale and sub-meoscale processes play a fundamental role in the redistribution of heat, salt, and marinebiomass. Mesoscale eddies carry waters with different properties from their surroundings, and sub-mesoscale(SMS) processes act to extract properties and energy from the mesoscale flow field and transfer them to scaleswhere mixing occurs. In particular, the SMS physical forcing can lead to biological and chemical responses astime scales of SMS motions and phytoplankton growth coincide.Physical-biogeochemical SMS coupling has mostly been studied near ocean margins and ocean frontal sys-tems. We report first results from an open-ocean study carried out north of the archipelago of Cape Verde,employing simultaneous observations from 5 gliders. Each glider recorded temperature, salinity, chlorophyll,dissolved oxygen and turbidity for the duration of 49 days in Spring 2010. A 45 by 45 km wide area was sampledusing butterfly shaped courses, to optimize the coverage of the whole area and the intercalibration of the gliders.The aims of the experiment include (i) the quantification of the SMS variability in the recorded parameters in boththe surface mixed layer and the thermocline including the upper part of the oxygen minimum zone (OMZ) and (ii)the demonstration of the coupling between physical processes (lateral and vertical advection) and biogeochemicalprocesses (phytoplankton biomass, oxygen production/consumption, fertilization by Saharan dust).During deployment period the gliders traveled about 3800 km and performed more than 3000 dives. Overthe course of the experiment the gliders observed significant variability in form of gradual seasonal changes ofthermohaline properties, internal waves, and meso-scale features that appeared to drift by with the backgroundcurrent. Below the mixed layer, changes in oxygen, and salinity imply spatio-temporal variability of the ratio ofNorth to South Atlantic waters. In addition, pronounced SMS variability is found, which might be important for thevertical fluxes of nutrients and oxygen between the OMZ and the mixed layer. An analysis of the scale-dependenceof the different parameters is shown. We have further implemented the methodology of Merkelbach et al. (2010),to derive profiles of vertical velocities from the gliders’ dives. The relation between the vertical velocities and theinternal wave field is presented. The oxygen measurements revealed a shallow lense of extremely low oxygen –significant lower than that within the OMZ - which is thought to originate from the African continental slope. Theglider measurements appear to be sensitive to the deposition of dust in the ocean because there are indicationsfor the correspondence between glider-derived turbidity and satellite-inferred aerosol optical depth. While beyondthe scope of the present study, the combination of turbidity and chlorophyll measurements might thus open theopportunity to study the effect of fertilization by Saharan dust on primary production in the tropical North Atlantic.In this respect, a comparison between glider and satellite-derived chlorophyll fluorescence will also be presented.

Glider fleet-based, multi-parameter observations in the tropical Northeast Atlantic

Abstract

Similar works

Full text

Available Versions

OceanRep

OceanRep

OceanRep