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Multi‐Century Impacts of Ice Sheet Retreat on Sea Level and Ocean Tides in Hudson Bay

Abstract.

"Past and modern large‐scale ice sheet loss results in geographically variable sea level changes. At present, in Hudson Bay, Canada, sea level is decreasing due to glacial isostatic adjustment, which represents a departure from the globally averaged sea level rise. However, there are large uncertainties in future sea level trends with further polar ice sheet retreat in the coming centuries. Sea level changes affect ocean tides considerably because tides are highly sensitive to changes in bathymetry. Here, we present multi‐century sea level projections associated with a suite of past and future ice loss scenarios and consider the impact of these changes on ocean tides[...]"

Source: Advancing Earth and Space Science
Authors: A.‐M. Hayden et al.
DOI: https://doi.org/10.1029/2019JC015104

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Ideas and perspectives: A strategic assessment of methane and nitrous oxide measurements in the marine environment

Abstract.

"In the current era of rapid climate change, accurate characterization of climate-relevant gas dynamics – namely production, consumption, and net emissions – is required for all biomes, especially those ecosystems most susceptible to the impact of change. Marine environments include regions that act as net sources or sinks for numerous climate-active trace gases including methane (CH4) and nitrous oxide (N2O). The temporal and spatial distributions of CH4 and N2O are controlled by the interaction of complex biogeochemical and physical processes. To evaluate and quantify how these mechanisms affect marine CH4 and N2O cycling requires a combination of traditional scientific disciplines including oceanography, microbiology, and numerical modeling[...]"

Source: Biogeosciences
Authors: Samuel T. Wilson et al.
DOI: https://doi.org/10.5194/bg-17-5809-2020

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Permian–Triassic mass extinction pulses driven by major marine carbon cycle perturbations

Abstract.

"The Permian/Triassic boundary approximately 251.9 million years ago marked the most severe environmental crisis identified in the geological record, which dictated the onwards course for the evolution of life. Magmatism from Siberian Traps is thought to have played an important role, but the causational trigger and its feedbacks are yet to be fully understood. Here we present a new boron-isotope-derived seawater pH record from fossil brachiopod shells deposited on the Tethys shelf that demonstrates a substantial decline in seawater pH coeval with the onset of the mass extinction in the latest Permian. Combined with carbon isotope data, our results are integrated in a geochemical model that resolves the carbon cycle dynamics as well as the ocean redox conditions[...]"

Source: Nature Geoscience
Authors: Hana Jurikova et al.
DOI: https://doi.org/10.1038/s41561-020-00646-4

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Imprint of Trace Dissolved Oxygen on Prokaryoplankton Community Structure in an Oxygen Minimum Zone

Abstract.

"The Eastern Tropical North Pacific (ETNP) is a large, persistent, and intensifying oxygen minimum zone (OMZ) that accounts for almost half of the total area of global OMZs. Within the OMZ core (∼350–700 m depth), dissolved oxygen is typically near or below the analytical detection limit of modern sensors (∼10 nM). Steep oxygen gradients above and below the OMZ core lead to vertical structuring of microbial communities that also vary between particle-associated (PA) and free-living (FL) size fractions. Here, we use 16S amplicon sequencing (iTags) to analyze the[...]"

Source: Frotiers in the Marine Science
Authors: Luis Medina Faull et al.
DOI: https://doi.org/10.3389/fmars.2020.00360

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Enhanced Organic Carbon Burial in Sediments of Oxygen Minimum Zones Upon Ocean Deoxygenation

Abstract.

"Oxygen minimum zones (OMZs) in the ocean are expanding. This expansion is attributed to global warming and may continue over the next 10 to 100 kyrs due to multiple climate CO2-driven factors. The expansion of oxygen-deficient waters has the potential to enhance organic carbon burial in marine sediments, thereby providing a negative feedback on global warming. Here, we study the response of dissolved oxygen in the ocean to increased phosphorus and iron inputs due to CO2-driven enhanced weathering and increased dust emissions, respectively. We use an ocean biogeochemical model[...]"

Source: frontiers in the Marine Science
Authors: Itzel Ruvalcaba Baroni et al.
DOI: https://doi.org/10.3389/fmars.2019.00839

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Heat and carbon coupling reveals ocean warming due to circulation changes

Abstract.

Anthropogenic global surface warming is proportional to cumulative carbon emissions1,2,3; this relationship is partly determined by the uptake and storage of heat and carbon by the ocean4. The rates and patterns of ocean heat and carbon storage are influenced by ocean transport, such as mixing and large-scale circulation5,6,7,8,9,10. However, existing climate models do not accurately capture the observed patterns of ocean warming, with a large spread in their projections of ocean circulation and ocean heat uptake8,11. Additionally, assessing the influence of ocean circulation changes (specifically, the redistribution of heat by resolved advection) on patterns[...]"

Source: Nature
Authors: Ben Bronselaer et al.
DOI: https://doi.org/10.1038/s41586-020-2573-5

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Early deglacial CO2 release from the Sub-Antarctic Atlantic and Pacific oceans

Abstract.

"Over the last deglaciation there were two transient intervals of pronounced atmospheric CO2 rise; Heinrich Stadial 1 (17.5-15 kyr) and the Younger Dryas (12.9-11.5 kyr). Leading hypotheses accounting for the increased accumulation of CO2 in the atmosphere at these times invoke deep ocean carbon being released from the Southern Ocean and an associated decline in the global efficiency of the biological carbon pump. Here we present new deglacial surface seawater pH and CO2sw records from the Sub-Antarctic regions of the Atlantic [...]"

 

Source: Science Direct
Autors: R. Shuttleworth et al.
DOI: https://doi.org/10.1016/j.epsl.2020.116649

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Seasonal variability of Air-Sea Fluxes in two contrasting basins of the north Indian Ocean

Abstract.

"Latent Heat Flux (LHF) and Sensible Heat Flux (SHF) are the two important parameters in air-sea interactions and hence have significant implications for any coupled ocean-atmospheric model. These two fluxes are conventionally computed from met-ocean parameters using bulk aerodynamic formulations; or the Coupled Ocean Atmosphere Response Experiment (COARE) bulk flux algorithms. Here COARE 3.5 algorithm is used to estimate the heat flux from two Ocean Moored Buoy Network for northern Indian Ocean[...]"

 

Source: Science Direct
Authors: Samar Kumar Ghose et al.
DOI: https://doi.org/10.1016/j.dynatmoce.2020.101183

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Organic matter composition and heterotrophic bacterial activity at declining summer sea ice in the central Arctic Ocean

Abstract.

"The Arctic Ocean is highly susceptible to climate change as evidenced by rapid warming and the drastic loss of sea ice during summer. The consequences of these environmental changes for the microbial cycling of organic matter are largely unexplored. Here, we investigated the distribution and composition of dissolved organic matter (DOM) along with heterotrophic bacterial activity in seawater and sea ice of the Eurasian Basin at the time of the record ice minimum in 2012. Bacteria in seawater were highly responsive to fresh organic matter and remineralized on average 55% of primary production in the upper mixed layer. Correlation analysis showed that the accumulation of dissolved combined carbohydrates (DCCHO) and dissolved[...]"

 

Source: Association for the Sciences Limnology and Oceanography
Authors: Judith Piontek et al.
DOI: https://doi.org/10.1002/lno.11639

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An ice–climate oscillatory framework for Dansgaard–Oeschger cycles

Abstract.

"Intermediate glacial states were characterized by large temperature changes in Greenland and the North Atlantic, referred to as Dansgaard–Oeschger (D–O) variability, with some transitions occurring over a few decades. D–O variability included changes in the strength of the Atlantic meridional overturning circulation (AMOC), temperature changes of opposite sign and asynchronous timing in each hemisphere, shifts in the mean position of the Intertropical Convergence Zone and variations in atmospheric CO2[...]"

 

Source: Nature Reviews Earth and Environment
Authors: Laurie C. Menviel et al.
DOI: https://doi.org/10.1038/s43017-020-00106-y

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