The regulation of oxygen to low concentrations in marine oxygen-minimum zones
"The Bay of Bengal hosts persistent, measurable, but sub-micromolar, concentrations of oxygen in its oxygen-minimum zone (OMZ). Such low-oxygen conditions are not necessarily rare in the global ocean and seem also to characterize the OMZ of the Pescadero Basin in the Gulf of California, as well as the outer edges of otherwise anoxic OMZs, such as can be found, for example, in the Eastern Tropical North Pacific. We show here that biological controls on oxygen consumption are required to allow the semistable persistence of low-oxygen conditions in OMZ settings; otherwise, only small changes in physical mixing or rates of primary production would drive the OMZ between anoxic and oxic states with potentially large swings in oxygen concentration. [...]"
Source: Journal of Marine Research
Authors: Don E. Canﬁeld et al.
No detectable Weddell Sea Antarctic Bottom Water export during the Last and Penultimate Glacial Maximum
"Weddell Sea-derived Antarctic Bottom Water (AABW) is one of the most important deep water masses in the Southern Hemisphere occupying large portions of the deep Southern Ocean (SO) today. While substantial changes in SO-overturning circulation were previously suggested, the state of Weddell Sea AABW export during glacial climates remains poorly understood. [...]"
Source: Nature Communications
Authors: Huang Huang et al.
Physical and biogeochemical impacts of RCP8.5 scenario in the Peru upwelling system
"The northern Humboldt current system (NHCS or Peru upwelling system) sustains the world's largest small pelagic fishery. While a nearshore surface cooling has been observed off southern Peru in recent decades, there is still considerable debate on the impact of climate change on the regional ecosystem. This calls for more accurate regional climate projections of the 21st century, using adapted tools such as regional eddy-resolving coupled biophysical models. [...]"
Source: Biogeosciences (preprint)
Authors: Vincent Echevin et al.
Anaerobic Activity Is a Big Contributor in Marine “Dead Zones”
Climate models that do not account for anaerobic microbial activity may underestimate future expansion of oxygen-depleted waters.
"Certain parts of Earth’s oceans are so oxygen depleted that they can hardly sustain life. Climate models predict that these “dead zones” will expand as global warming progresses, affecting ecosystems, fisheries, and the climate itself. Now Lengger et al. provide new evidence that such predictions do not adequately account for the activity of anaerobic microbes that consume inorganic carbon within dead zones. [...]"
Modulation of the North Atlantic deoxygenation by the slowdown of the nutrient stream
"Western boundary currents act as transport pathways for nutrient-rich waters from low to high latitudes (nutrient streams) and are responsible for maintaining midlatitude and high-latitude productivity in the North Atlantic and North Pacific. This study investigates the centennial oxygen (O2) and nutrient changes over the Northern Hemisphere in the context of the projected warming and general weakening of the Atlantic Meridional Overturning Circulation (AMOC) in a subset of Earth system models included in the CMIP5 catalogue. In all models examined, the Atlantic warms faster than the Pacific Ocean, resulting in a greater basin-scale solubility decrease. [...]"
Authors: Filippos Tagklis et al.
Record-Setting Ocean Warmth Continued in 2019
"Human-emitted greenhouse gases (GHGs) have resulted in a long-term and unequivocal warming of the planet (IPCC, 2019). More than 90% of the excess heat is stored within the world’s oceans, where it accumulates and causes increases in ocean temperature (Rhein et al., 2013; Abram et al., 2019). Because the oceans are the main repository of the Earth’s energy imbalance, measuring ocean heat content (OHC) is one of the best way to quantify the rate of global warming (Trenberth et al., 2016; Von Schuckmann et al., 2016; Cheng et al., 2018). [...]"
Source: Advances in Atmospheric Sciences
Authors: Lijing Cheng et al.
Record-setting ocean warmth continued in 2019
"A new analysis shows the world's oceans were the warmest in 2019 than any other time in recorded human history, especially between the surface and a depth of 2,000 meters. The study, conducted by an international team of 14 scientists from 11 institutes across the world, also concludes that the past ten years have been the warmest on record for global ocean temperatures, with the past five years holding the highest record. [...]"
Implications of different nitrogen input sources for potential production and carbon flux estimates in the coastal Gulf of Mexico (GOM)
and Korean Peninsula coastal waters
"The coastal Gulf of Mexico (GOM) and coastal sea off the Korean Peninsula (CSK) both suffer from human-induced eutrophication. We used a nitrogen (N) mass balance model in two different regions with different nitrogen input sources to estimate organic carbon fluxes and predict future carbon fluxes under different model scenarios. The coastal GOM receives nitrogen predominantly from the Mississippi and Atchafalaya rivers and atmospheric nitrogen deposition is only a minor component in this region. [...]"
Source: Ocean Science
Authors: Jongsun Kim et al.
Fish Diet Shifts Associated with the Northern Gulf of Mexico Hypoxic Zone
"The occurrence of low dissolved oxygen (hypoxia) in coastal waters may alter trophic interactions within the water column. This study identified a threshold at which hypoxia in the northern Gulf of Mexico (NGOMEX) alters composition of fish catch and diet composition (stomach contents) of fishes using fish trawl data from summers 2006–2008. Hypoxia in the NGOMEX impacted fish catch per unit effort (CPUE) and diet below dissolved oxygen thresholds of 1.15 mg L−1 (for fish CPUE) and 1.71 mg L−1 (for diet). CPUE of many fish species was lower at hypoxic sites (≤ 1.15 mg L −1) as compared to normoxic regions (> 1.15 mg L −1), including the key recreational or commercial fish species Atlantic croaker Micropogonias undulatus and red snapper Lutjanus campechanus. [...]"
Source: Estuaries and Coasts
Authors: Cassandra N. Glaspie et al.
Upwelling Bays: How Coastal Upwelling Controls Circulation, Habitat, and Productivity in Bays
"Bays in coastal upwelling regions are physically driven and biochemically fueled by their interaction with open coastal waters. Wind-driven flow over the shelf imposes a circulation in the bay, which is also influenced by local wind stress and thermal bay–ocean density differences. Three types of bays are recognized based on the degree of exposure to coastal currents and winds (wide-open bays, square bays, and elongated bays), and the characteristic circulation and stratification patterns of each type are described. Retention of upwelled waters in bays allows for dense phytoplankton blooms that support productive bay ecosystems. [...]"
Source: Annual Review of Marine Science
Authors: John L. Largier