Antarctic offshore polynyas linked to Southern Hemisphere climate anomalies
"Offshore Antarctic polynyas—large openings in the winter sea ice cover—are thought to be maintained by a rapid ventilation of deep-ocean heat through convective mixing. These rare phenomena may alter abyssal properties and circulation, yet their formation mechanisms are not well understood. Here we demonstrate that concurrent upper-ocean preconditioning and meteorological perturbations are responsible for the appearance of polynyas in the Weddell Sea region of the Southern Ocean. [...]"
Authors: Ethan C. Campbell et al.
Ocean ventilation and deoxygenation in a warming world: introduction and overview
"Changes of ocean ventilation rates and deoxygenation are two of the less obvious but important indirect impacts expected as a result of climate change on the oceans. They are expected to occur because of (i) the effects of increased stratification on ocean circulation and hence its ventilation, due to reduced upwelling, deep-water formation and turbulent mixing, (ii) reduced oxygenation through decreased oxygen solubility at higher surface temperature, and (iii) the effects of warming on biological production, respiration and remineralization. The potential socio-economic consequences of reduced oxygen levels on fisheries and ecosystems may be far-reaching and significant. [...]"
Source: The Royal Society
Authors: John G. Shepherd, Peter G. Brewer, Andreas Oschlies, Andrew J. Watson
Decadal oxygen change in the eastern tropical North Atlantic
"Repeat shipboard and multi-year moored observations obtained in the oxygen minimum zone (OMZ) of the eastern tropical North Atlantic (ETNA) were used to study the decadal change in oxygen for the period 2006–2015. Along 23° W between 6 and 14° N, oxygen decreased with a rate of −5.9 ± 3.5 µmol kg−1 decade−1 within the depth covering the deep oxycline (200–400 m), while below the OMZ core (400–1000 m) oxygen increased by 4.0 ± 1.6 µmol kg−1 decade−1 on average. The inclusion of these decadal oxygen trends in the recently estimated oxygen budget for the ETNA OMZ suggests a weakened ventilation of the upper 400 m, whereas the ventilation strengthened homogeneously below 400 m. [...]"
Source: Ocean Science
Authors: Johannes Hahn, Peter Brandt, Sunke Schmidtko and Gerd Krahmann
Hypoxic induced decrease in oxygen consumption in cuttlefish (Sepia officinalis) is associated with minor increases in mantle octopine [...]
"The common cuttlefish (Sepia officinalis), a dominant species in the north-east Atlantic ocean and Mediterranean Sea, is potentially subject to hypoxic conditions due to eutrophication of coastal waters and intensive aquaculture. Here we initiate studies on the biochemical response to an anticipated level of hypoxia. Cuttlefish challenged for one hour at an oxygen level of 50% dissolved oxygen saturation showed a decrease in oxygen consumption of 37% associated with an 85% increase in ventilation rate. [...]"
Source: Frontiers in Marine Physiology
Authors: Juan C. Capaz et al.