Glacial heterogeneity in Southern Ocean carbon storage abated by fast South Indian deglacial carbon release
"Past changes in ocean 14C disequilibria have been suggested to reflect the Southern Ocean control on global exogenic carbon cycling. Yet, the volumetric extent of the glacial carbon pool and the deglacial mechanisms contributing to release remineralized carbon, particularly from regions with enhanced mixing today, remain insufficiently constrained. Here, we reconstruct the deglacial ventilation history of the South Indian upwelling hotspot near Kerguelen Island, using high-resolution 14C-dating of smaller-than-conventional foraminiferal samples and multi-proxy deep-ocean oxygen[...]"
Source: Nature Communications
Authors: Julia Gottschalk et al.
In situ observations show vertical community structure of pelagic fauna in the eastern tropical North Atlantic off Cape Verde
"Distribution patterns of fragile gelatinous fauna in the open ocean remain scarcely documented. Using epi-and mesopelagic video transects in the eastern tropical North Atlantic, which features a mild but intensifying midwater oxygen minimum zone (OMZ), we established one of the first regional observations of diversity and abundance of large gelatinous zooplankton. We quantified the day and night vertical distribution of 46 taxa in relation to environmental conditions. While distribution may be driven by multiple factors, abundance peaks of individual taxa were observed in the OMZ[...]"
Source: Nature Scientific Reports
Authors: H. J. T. Hoving et al.
The influence of plastic pollution and ocean change on detrital decomposition
"Plastic pollution and ocean change have mostly been assessed separately, missing potential interactions that either enhance or reduce future impacts on ecosystem processes. Here, we used manipulative experiments with outdoor mesocosms to test hypotheses about the interactive effects of plastic pollution, ocean warming and acidification on macrophyte detrital decomposition. These experiments focused on detritus from kelp, Ecklonia radiata, and eelgrass, Zostera muelleri, and included crossed treatments of (i) no, low and high plastic pollution, (ii) current/future ocean temperatures, and (iii) ambient/future ocean partial pressure of carbon dioxide (pCO2). High levels of plastic pollution significantly reduced[...]"
Source: Science Direct
Authors: Sebastian G. Litchfield et al.
Southern Ocean carbon export efficiency in relation to temperature and primary productivity
"Satellite remote sensing and numerical models are widely used to estimate large-scale variations in ocean carbon export, but the relationship between export efficiency (e-ratio) of sinking organic carbon out of the surface ocean and its drivers remains poorly understood, especially in the Southern Ocean. Here, we assess the effects of temperature and primary productivity on e-ratio by combining particulate organic carbon export flux from in situ measurements during 1997–2013, environmental parameters from satellite products, and outputs from ocean biogeochemical models in the Southern Ocean. Results show that “High Productivity Low E-ratio” (HPLE) is a common phenomenon in the Subantarctic Zone and the Polar Frontal Zone, but not the Antarctic Zone[...]"
Source: Nature Scientific Reports
Authors: Gaojing Fan et al.
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.
EGU General Assembly 2021
Aims & scope
The EGU General Assembly 2021 will bring together geoscientists from all over the world to one meeting covering all disciplines of the Earth, planetary, and space sciences. The EGU aims to provide a forum where scientists, especially early career researchers, can present their work and discuss their ideas with experts in all fields of geoscience. The EGU is looking forward to cordially welcoming you at its General Assembly.
Start Date: 4/19/21
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.
New Webinar Series on Ocean Deoxygenation
Do you want to know more about deoxygenation in the ocean?
Join us for the upcoming webinar!
Wednesday, 9th December 2020, 15:00 h – 16:00 h CET
The Global Ocean Oxygen Network (IOC Expert Working Group GO2NE) starts a new series on ocean deoxygenation. The second webinar will take place 9 December 2020. The speakers will present latest science on the impacts of reduced oxygen in the open ocean and coastal zones. Each webinar will feature two presentations by a more senior and an earlier-career scientist, 20 minutes each followed by 10 minutes moderated discussion sessions.
Reviews and syntheses: Present, past, and future of the oxygen minimum zone in the northern Indian Ocean
"Decreasing concentrations of dissolved oxygen in the ocean are fuconsidered one of the main threats to marine ecosystems as they jeopardize the growth of higher organisms. They also alter the marine nitrogen cycle, which is strongly bound to the carbon cycle and climate. While higher organisms in general start to suffer from oxygen concentrations < ∼ 63 µM (hypoxia), the marine nitrogen cycle responds to oxygen concentration below a threshold of about 20 µM (microbial hypoxia), whereas anoxic processes dominate the nitrogen cycle at oxygen concentrations of < ∼ 0.05 µM (functional anoxia). The Arabian Sea and the Bay of Bengal are home to approximately 21 % of the total volume of ocean waters revealing microbial hypoxia. While in the Arabian Sea this oxygen minimum zone (OMZ) is also functionally anoxic[...]"
Authors: Tim Rixen et al.
Diversity and distribution of nitrogen fixation genes in the oxygen minimum zones of the world oceans
"Diversity and community composition of nitrogen (N) fixing microbes in the three main oxygen minimum zones (OMZs) of the world ocean were investigated using operational taxonomic unit (OTU) analysis of nifH clone libraries. Representatives of three of the four main clusters of nifH genes were detected. Cluster I sequences were most diverse in the surface waters, and the most abundant OTUs were affiliated with Alpha- and Gammaproteobacteria. Cluster II, III, and IV assemblages were most diverse at oxygen-depleted depths, and none of the sequences were closely related to sequences from cultivated organisms. The OTUs were biogeographically distinct for the most part – there was little overlap among regions, between depths, or between cDNA and DNA. In this study of all three OMZ regions, as well as from the few other published reports from individual OMZ sites, the dominance of a few OTUs was[...]"
Authors: Amal Jayakumar et al.
DOI: https://doi.org/10.5194/bg-17-5953-2020, 2020