University of Bern, Switzerland - Compound extreme events stress the oceans

Title:

Compound extreme events stress the oceans

 

Published:

University of Bern,  16 August 2022

https://www.unibe.ch/news/media_news/media_relations_e/media_releases/2022/media_releases_2022/compound_extreme_events_stress_the_oceans/index_eng.html

From the media release:

When marine heatwaves and ocean acidity extreme events co-occur, it can have severe impacts on marine ecosystems. Researchers at the Oeschger Center for Climate Change Research at the University of Bern have determined for the first time the frequency and drivers of these compound events and have projected them into the future.

 

ALSO SEE

 

Friedrich A. Burger, Jens Terhaar & Thomas L. Frölicher: Compound marine heatwaves and ocean acidity extremes. Nature Communications, 16. August 2022. Doi 10.1038/s41467-022-32120-7,  

https://doi.org/10.1038/s41467-022-32120-7

 

The Arctic Ocean might have been filled with freshwater during ice ages [Nature, 3 February 2021]

Title:

The Arctic Ocean might have been filled with freshwater during ice ages

 

Author:

Sharon Hoffmann

A palaeoceanographer based in Wilmington, North Caroline, USA

Published:

Nature, 3 February 2021

https://www.nature.com/articles/d41586-021-00208-7

From the article:

A geochemical study of sediments suggests that, during recent glacial periods, the Arctic Ocean was completely isolated from the world ocean, with fresh water filling the basin for thousands of years.

See also:

Title: 

Glacial episodes of a freshwater Arctic Ocean covered by a thick ice shelf

 

Authors: 

Walter Geibert, Jens Matthiessen, Ingrid Stimac, Jutta Wollenburg & Ruediger Stein

(All from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany. Ruediger Stein is also affiliated with MARUM & the Faculty of Geosciences, University of Bremen, Germany)

 

Published: 

Nature, 3 February 2021

https://www.nature.com/articles/s41586-021-03186-y

Abstract:

Following early hypotheses about the possible existence of Arctic ice shelves in the past1,2,3, the observation of specific erosional features as deep as 1,000 metres below the current sea level confirmed the presence of a thick layer of ice on the Lomonosov Ridge in the central Arctic Ocean and elsewhere4,5,6. Recent modelling studies have addressed how an ice shelf may have built up in glacial periods, covering most of the Arctic Ocean7,8. So far, however, there is no irrefutable marine-sediment characterization of such an extensive ice shelf in the Arctic, raising doubt about the impact of glacial conditions on the Arctic Ocean. Here we provide evidence for at least two episodes during which the Arctic Ocean and the adjacent Nordic seas were not only covered by an extensive ice shelf, but also filled entirely with fresh water, causing a widespread absence of thorium-230 in marine sediments. We propose that these Arctic freshwater intervals occurred 70,000–62,000 years before present and approximately 150,000–131,000 years before present, corresponding to portions of marine isotope stages 4 and 6. Alternative interpretations of the first occurrence of the calcareous nannofossil Emiliania huxleyi in Arctic sedimentary records would suggest younger ages for the older interval. Our approach explains the unexpected minima in Arctic thorium-230 records9 that have led to divergent interpretations of sedimentation rates10,11 and hampered their use for dating purposes. About nine million cubic kilometres of fresh water is required to explain our isotopic interpretation, a calculation that we support with estimates of hydrological fluxes and altered boundary conditions. A freshwater mass of this size—stored in oceans, rather than land—suggests that a revision of sea-level reconstructions based on freshwater-sensitive stable oxygen isotopes may be required, and that large masses of fresh water could be delivered to the north Atlantic Ocean on very short timescales.

Catastrophic Trigger That Led to Earth's Largest Mass Extinction Revealed in Fossils

Title:

Catastrophic Trigger That Led to Earth's Largest Mass Extinction Revealed in Fossils

 

Author:

David Nield

 

Published:

Science Alert, 21 October 2020

https://www.sciencealert.com/scientists-find-the-geochemical-trigger-for-the-world-s-largest-ever-mass-extinction

 

From the article:

Scientists think they've finally come closer to identifying the cause of Earth's worst mass extinction, by tracking down the geochemical trigger that may have started it all.  Known as the Great Dying, the Permian-Triassic extinction event happened around 252 million years ago. The new research is based on a study of fossil shells left behind by clam-like brachiopods in what today is the Southern Alps.

Note from blog owner:

The research was published in a scholarly publication.

Title:

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

Authors:

Hana Jurikova, Marcus Gutjahr, Klaus Wallmann, Sascha Flögel, Volker Liebetrau, Renato Posenato, Lucia Angiolini, Claudio Garbelli, Uwe Brand, Michael Wiedenbeck & Anton Eisenhauer 

Published:

Nature Geoscience, 19 October 2020

https://www.nature.com/articles/s41561-020-00646-4

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 and nitrogen isotope turnover. We find that the initial ocean acidification was intimately linked to a large pulse of carbon degassing from the Siberian sill intrusions. We unravel the consequences of the greenhouse effect on the marine environment, and show how elevated sea surface temperatures, export production and nutrient input driven by increased rates of chemical weathering gave rise to widespread deoxygenation and sporadic sulfide poisoning of the oceans in the earliest Triassic. Our findings enable us to assemble a consistent biogeochemical reconstruction of the mechanisms that resulted in the largest Phanerozoic mass extinction.

New research shows that the early Earth, home to some of our planet’s first lifeforms, may have been a real-life “waterworld”– without a continent in sight

Title:
Early Earth may have been a sunken 'waterworld'

Published:
HeritageDaily, 2 March 2020

From the article:
"New research shows that the early Earth, home to some of our planet’s first lifeforms, may have been a real-life “waterworld”– without a continent in sight.

The study, which appears March 2 in Nature Geoscience, takes advantage of a quirk of hydrothermal chemistry to suggest that the surface of Earth was likely covered by a global ocean 3.2 billion years ago. It may even have looked a bit like the post-apocalyptic, and land-free, future imagined in Costner’s infamous film Waterworld."

To read this article:
https://www.heritagedaily.com/2020/03/early-earth-may-have-been-a-sunken-waterworld/126009

To read the scholarly article:
Johnson, B.W., Wing, B.A. (2020). Limited Archaean continental emergence reflected in an early Archaean 18O-enriched ocean. Nature Geoscience, 13, 243–248. https://doi.org/10.1038/s41561-020-0538-9