Open ocean dead zones in the tropical North Atlantic Ocean
نویسندگان
چکیده
Here we present first observations, from instrumentation installed on moorings and a float, of unexpectedly low (< 2 μmolkg) oxygen environments in the open waters of the tropical North Atlantic, a region where oxygen concentration does normally not fall much below 40 μmolkg. The low-oxygen zones are created at shallow depth, just below the mixed layer, in the euphotic zone of cyclonic eddies and anticyclonic-modewater eddies. Both types of eddies are prone to high surface productivity. Net respiration rates for the eddies are found to be 3 to 5 times higher when compared with surrounding waters. Oxygen is lowest in the centre of the eddies, in a depth range where the swirl velocity, defining the transition between eddy and surroundings, has its maximum. It is assumed that the strong velocity at the outer rim of the eddies hampers the transport of properties across the eddies boundary and as such isolates their cores. This is supported by a remarkably stable hydrographic structure of the eddies core over periods of several months. The eddies propagate westward, at about 4 to 5 km day, from their generation region off the West African coast into the open ocean. High productivity and accompanying respiration, paired with sluggish exchange across the eddy boundary, create the “dead zone” inside the eddies, so far only reported for coastal areas or lakes. We observe a direct impact of the open ocean dead zones on the marine ecosystem as such that the diurnal vertical migration of zooplankton is suppressed inside the eddies.
منابع مشابه
Contributions of Atlantic Ocean to June-August Rainfall over Uganda and Western Kenya
This study investigates the contributions of Atlantic Ocean to June-August rainfall over Uganda and western Kenya (KU). The study has utilized the datasets including precipitation from the Global Precipitation Climatology Centre, North Atlantic Oscillation Index (NAOI), South Atlantic Ocean Dipole Index (SAODI), ERA-interim reanalysis, and the Atlantic Ocean Sea Surface Temperature (SST). Singu...
متن کاملHidden biosphere in an oxygen-deficient Atlantic open ocean eddy: Future implications of ocean 1 deoxygenation on primary production in the eastern tropical North Atlantic 2 3
متن کامل
Fast teleconnections to the tropical Atlantic sector from Atlantic thermohaline adjustment
[1] We examine the first decade of adjustment of the North Atlantic climate following an abrupt freshening of the high North Atlantic and resulting slowdown of the Atlantic meridional overturning circulation (AMOC) in a coupled model, with reference to previously proposed teleconnection mechanisms. After an initial ocean-driven cooling at the subtropical-subpolar gyre boundary, subsequent equat...
متن کاملNitrous oxide in the North Atlantic Ocean
In order to get a comprehensive picture of the distribution of nitrous oxide (N2O) in the North Atlantic Ocean, measurements of dissolved nitrous oxide were made during three cruises in the tropical, subtropical and coldtemperate North Atlantic Ocean in October/November 2002, March/April 2004, and May 2002, respectively. To account for the history of atmospheric N2O, we suggest a new depthdepen...
متن کاملTropical Pacific/Atlantic Ocean Interactions at Multi-Decadal Time Scales
Analysis of sea surface temperature (SST) observations suggests a pan-oceanic interaction between the tropical Pacific and the Atlantic Ocean at multi-decadal time scales, such that periods of anomalously high SSTs in the eastern tropical Pacific are followed by a basinwide SST dipole in the Atlantic Ocean with a time delay of a few decades. The SST anomaly structure in the Atlantic Ocean is re...
متن کامل