Changes in phytoplankton concentration now drive increased Arctic Ocean primary production
"Historically, sea ice loss in the Arctic Ocean has promoted increased phytoplankton primary production because of the greater open water area and a longer growing season. However, debate remains about whether primary production will continue to rise should sea ice decline further. Using an ocean color algorithm parameterized for the Arctic Ocean, we show that primary production increased by 57% between 1998 and 2018. Surprisingly, whereas increases were due to widespread sea ice loss during the first decade[...]"
Source: American Association For The Advancement Of Science
Authors: K. M. Lewis et al.
Recent Changes in Deep Ventilation of the Mediterranean Sea; Evidence From Long-Term Transient Tracer Observations
"The Mediterranean Sea is a small region of the global ocean but with a very active overturning circulation that allows surface perturbations to be transported to the interior ocean. Understanding of ventilation is important for understanding and predicting climate change and its impact on ocean ecosystems. To quantify changes of deep ventilation, we investigated the spatiotemporal variability of transient tracers (i.e., CFC-12 and SF6) observations combined with temporal evolution of hydrographic and oxygen observations in the Mediterranean Sea from 13 cruises conducted during 1987–2018, with emphasize on the update from 2011 to 2018. Spatially, both the Eastern and Western Mediterranean Deep Water (EMDW and WMDW) show a general west-to-east gradient[...]"
Authors: Pingyang Li et al.
Chromium reduction and associated stable isotope fractionation restricted to anoxic shelf waters in the Peruvian Oxygen Minimum Zone
"The marine chromium (Cr) cycle is still insufficiently understood, in particular the mechanisms modulating the spatial distribution of dissolved stable Cr isotopes in seawater. Redox transformations between its main oxidation states, Cr(VI) and Cr(III), have been held accountable for the observed tight inverse logarithmic relationship between the dissolved Cr concentration [Cr] and its isotopic composition (δ53Cr), whereby isotopically light Cr(III) is removed in surface waters and oxygen minimum zones[...]"
Source: Science Direct
Authors: Philipp Nasemann et al.
Benthic fluxes of oxygen and nutrients under the influence of macrobenthic fauna on the periphery of the intermittently hypoxic zone in the Baltic Sea
"Understanding the role of benthic organisms in marine sediments is becoming increasingly important with the growing problem of eutrophication of marine ecosystems around the world, including the Baltic Sea. Therefore, we have conducted a series of incubation experiments on sediment cores collected from sites characterized by varying oxygen conditions and measured the influx (uptake by sediment) of oxygen as well as the sediment–water exchange of phosphate, ammonia and silicate.[...]"
Source: Science Direct
Authors: Halina Kendzierska et al.
Geoengineered Ocean Vertical Water Exchange Can Accelerate Global Deoxygenation
"Ocean deoxygenation is a threat to marine ecosystems. We evaluated the potential of two ocean intervention technologies, that is, “artificial downwelling (AD)” and “artificial upwelling (AU),” for remedying the expansion of Oxygen Deficient Zones (ODZs). The model‐based assessment simulated AD and AU implementations for 80 years along the eastern Pacific ODZ.[...]"
Source: Advancing Earth And Space Science
Authors: Ellias Yuming Feng et al.
Ocean Carbon Uptake Under Aggressive Emission Mitigation
"Nearly every nation has signed the UNFCC Paris Agreement, committing to mitigate global anthropogenic carbon (Cant) emissions and limit global mean temperature increase to 1.5 °C. A consequence of emission mitigation is reduced efficiency of ocean Cant uptake, which is driven by mechanisms that have not been studied in detail. The historical pattern of continual increase in atmospheric CO2 has resulted in a proportional increase in Cant uptake. [...]"
Authors: Sean Ridge and Galen McKinley
Monitoring ocean biogeochemistry with autonomous platforms
"Human activities have altered the state of the ocean, leading to warming, acidification and deoxygenation. These changes impact ocean biogeochemistry and influence ecosystem functions and ocean health. The long-term global effects of these changes are difficult to predict using current satellite sensing and traditional in situ observation techniques. [...]"
Source: Nature Reviews Earth & Environment
Authors: Fei Chai et al.
Substrate regulation leads to differential responses of microbial ammonia-oxidizing communities to ocean warming
"In the context of continuously increasing anthropogenic nitrogen inputs, knowledge of how ammonia oxidation (AO) in the ocean responds to warming is crucial to predicting future changes in marine nitrogen biogeochemistry. Here, we show divergent thermal response patterns for marine AO across a wide onshore/offshore trophic gradient. [...]"
Source: Nature Communications
Authors: Zhen-Zhen Zheng et al.
Contrasting decadal trends of subsurface excess nitrate in the western and eastern North Atlantic Ocean
"Temporal variations in excess nitrate (DINxs) relative to dissolved inorganic phosphorus (DIP) were evaluated using datasets derived from repeated measurements along meridional and zonal transects in the upper (200–600 m) North Atlantic (NAtl) between the 1980s and 2010s. The analysis revealed that the DINxs trend in the western NAtl differed from that in the eastern NAtl. In the western NAtl, which has been subject to atmospheric nitrogen deposition (AND) from the USA, the subsurface DINxs concentrations have increased over the last 2 decades. [...]"
Authors: Jin-Yu Terence Yang et al.
Atmospheric deposition of organic matter at a remote site in the central Mediterranean Sea: implications for the marine ecosystem
"Atmospheric fluxes of dissolved organic matter (DOM) were studied for the first time on the island of Lampedusa, a remote site in the central Mediterranean Sea (Med Sea), between 19 March 2015 and 1 April 2017. The main goals of this study were to quantify total atmospheric deposition of DOM in this area and to evaluate the impact of Saharan dust deposition on DOM dynamics in the surface waters of the Mediterranean Sea. Our data show high variability in DOM deposition rates without a clear seasonality and a dissolved organic carbon (DOC) input from the atmosphere of 120.7 mmol DOC m−2 yr−1. [...]"
Authors: Yuri Galletti et al.
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