Hydrostatic pressure is the universal key driver of microbial evolution in the deep ocean and beyond
"Oceans cover approximately 70% of the Earth’s surface, and microbes comprise 90% of the ocean biomass and are regarded as an important ‘hidden’ driver of essential elemental cycling, such as carbon cycling, in the oceans (Karl, 2007; Salazar and Sunagawa, 2017). Although the general public – even many scientists – think of the oceans as unified, stable water systems, they contain varied environments, including extreme environments such as oxygen-deficient zones, oligotrophic open ocean, polar water regions, deep ocean[...]"
Source: Environmental Microbiology Reports
Authors: Xiang Xiao et al.
Physical Mechanisms Driving Oxygen Subduction in the Global
"Future changes in subduction are suspected to be critical for the ocean deoxygenation predicted by climate models over the 21st century. However, the drivers of global oxygen subduction have not been fully described or quantified. Here, we address the physical mechanisms responsible for the oxygen transport across the late‐winter mixed layer base and their relation with water mass formation. Up to 70% of the global oxygen uptake takes place during Mode Water subduction mostly in the Southern Ocean[...]"
Source: Advancing Earth and Space Science
Authors: Esther Portela et al.
Increasing ocean stratification over the past half-century
"Seawater generally forms stratified layers with lighter waters near the surface and denser waters at greater depth. This stable configuration acts as a barrier to water mixing that impacts the efficiency of vertical exchanges of heat, carbon, oxygen and other constituents. Previous quantification of stratification change has been limited to simple differencing of surface and 200-m depth changes and has neglected the spatial complexity of ocean density change. Here, we quantify changes in ocean stratification down[...]"
Source: Nature Climate Change
Authors: Guancheng Li et al.
Ventilation of the Upper Oxygen Minimum Zone in the Coastal Region Off Mexico: Implications of El Niño 2015–2016
"As a result of anthropogenic activities, it has been predicted that the ocean will be challenged with rising temperature, increased stratification, ocean acidification, stronger more frequent tropical storms, and oxygen depletion. In the tropical Pacific off central Mexico all these phenomena are already occurring naturally, providing a laboratory from which to explore ocean biogeochemical dynamics that are predicted under future anthropogenic forcing conditions. "
Source: Frontiers in Marine Science
Authors: Pablo N. Trucco-Pignata et al.
Ventilation of the Northern Baltic Sea (Preprint)
"The Baltic Sea is a semi-enclosed, brackish water sea in northern Europe. The deep basins of the central Baltic Sea regularly show hypoxic conditions. In contrast, the northern parts of the Baltic Sea, the Bothnian Sea and Bay, are well oxygenated. Lateral inflows or a ventilation due to convection are possible mechanisms for high oxygen concentrations in the deep water of the northern Baltic Sea. [...]"
Source: Ocean Science
Authors: Thomas Neumann et al.
Periodic changes in the Cretaceous ocean and climate caused by marine redox see-saw
"Periodic changes in sediment composition are usually ascribed to insolation forcing controlled by Earth’s orbital parameters. During the Cretaceous Thermal Maximum at 97–91 Myr ago (Ma), a 37–50-kyr-long cycle that is generally believed to reflect obliquity forcing dominates the sediment record. [...]"
Source: Nature Geoscience
Authors: Klaus Wallmann et al.
Wind synoptic activity increases oxygen levels in the tropical Pacific Ocean
"The mechanisms controlling the variability of oxygen levels in the ocean are poorly quantified. We focus here on the impact of wind synoptic variability associated with tropical convective regions and extra‐tropical storms. Removing the wind higher frequencies of variability (2 days – 1 month) in an atmosphere reanalysis used to force an ocean model decreases wind stress by up to 20% in the tropics and 50% in the mid‐latitudes, weakening wind‐driven ocean circulation by 20%. Oxygen levels decrease by up to 10 mmol.m‐3 in tropical oceans and 30 mmol.m‐3 in subtropical gyres mainly due to changes in advective processes. [...]"
Source: Geophysical Research Letters
Authors: Olaf Duteil
Transport, properties, and life cycles of mesoscale eddies in the eastern tropical South Pacific
"The influence of mesoscale eddies on the flow field and the water masses, especially the oxygen distribution of the eastern tropical South Pacific, is investigated from a mooring, float, and satellite data set. Two anticyclonic (ACE1/2), one mode-water (MWE), and one cyclonic eddy (CE) are identified and followed in detail with satellite data on their westward transition with velocities of 3.2 to 6.0cms−1 from their generation region, the shelf of the Peruvian and Chilean upwelling regime, across the Stratus Ocean Reference Station (ORS; ∼ 20°S, 85°W) to their decaying region far west in the oligotrophic open ocean. [...]"
Source: Ocean Science
Authors: Rena Czeschel et al.
Oxygen Pathways and Budget for the Eastern South Pacific Oxygen Minimum Zone
"Ventilation of the eastern South Pacific Oxygen Minimum Zone (ESP‐OMZ) is quantified using climatological Argo and dissolved oxygen data, combined with reanalysis wind stress data. We (1) estimate all oxygen fluxes (advection and turbulent diffusion) ventilating this OMZ, (2) quantify for the first time the oxygen contribution from the subtropical versus the traditionally studied tropical‐equatorial pathway, and (3) derive a refined annual‐mean oxygen budget for the ESP‐OMZ. In the upper OMZ layer, net oxygen supply is dominated by tropical‐equatorial advection, with more than one‐third of this supply upwelling into the Ekman layer through previously unevaluated vertical advection, within the overturning component of the regional Subtropical Cell (STC). [...]"
Authors: P. J. Llanillo et al.
Biogeochemical Role of Subsurface Coherent Eddies in the Ocean: Tracer Cannonballs, Hypoxic Storms, and Microbial Stewpots?
"Subsurface eddies are known features of ocean circulation, but the sparsity of observations prevents an assessment of their importance for biogeochemistry. Here we use a global eddying (0.1°) ocean-biogeochemical model to carry out a census of subsurface coherent eddies originating from eastern boundary upwelling systems (EBUS) and quantify their biogeochemical effects as they propagate westward into the subtropical gyres. [...]"
Source: Global Biogeochemical Cycles
Authors: Ivy Frenger et al.
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