. | . |
Oceans were stressed preceding abrupt, prehistoric global warming by Staff Writers Chicago IL (SPX) Mar 09, 2021
Microscopic fossilized shells are helping geologists reconstruct Earth's climate during the Paleocene-Eocene Thermal Maximum (PETM), a period of abrupt global warming and ocean acidification that occurred 56 million years ago. Clues from these ancient shells can help scientists better predict future warming and ocean acidification driven by human-caused carbon dioxide emissions. Led by Northwestern University, the researchers analyzed shells from foraminifera, an ocean-dwelling unicellular organism with an external shell made of calcium carbonate. After analyzing the calcium isotope composition of the fossils, the researchers concluded that massive volcanic activity injected large amounts of carbon dioxide into the Earth system, causing global warming and ocean acidification. They also found that global warming and ocean acidification did not just passively affect foraminifera. The organisms also actively responded by reducing calcification rates when building their shells. As calcification slowed, the foraminifera consumed less alkalinity from seawater, which helped buffer increasing ocean acidity. "The formation and dissolution of calcium carbonate help regulate the acidity and alkalinity of seawater," said Northwestern's Andrew Jacobson, a senior author of the study. "Our calcium isotope data indicate that reduced foraminiferal calcification worked to dampen ocean acidification before and across the PETM." "This is a pretty new concept in the field," added Gabriella Kitch, the study's first author. "Previously, people thought that only the dissolution of carbonates at the sea floor could increase alkalinity of the ocean and buffer the effects of ocean acidification. But we are adding to existing studies that show decreased carbonate production has the same buffering effect." The research was published online last week (March 4) in the journal Geology. This is the first study to examine the calcium isotope composition of foraminifera to reconstruct conditions before and across the PETM and the third recent Northwestern study to find that ocean acidification - due to volcanic carbon dioxide emissions - preceded major prehistoric environmental catastrophes, such as mass extinctions, oceanic anoxic events and periods of intense global warming. Jacobson is a professor of Earth and planetary sciences at Northwestern's Weinberg College of Arts and Sciences. Kitch is a Ph.D. candidate and National Science Foundation Graduate Research Fellow in Jacobson's laboratory. Northwestern Earth science professors Bradley Sageman and Matthew Hurtgen, as well as collaborators from the University of California-Santa Cruz (UCSC) and the University of Kansas, coauthored the paper with Jacobson and Kitch.
Sorting microscopic shells Because each fossilized shell is about the size of a single grain of sand, UCSC researchers physically collected the tiny specimens by first identifying them under a microscope. After sorting the shells from bulk sediments, the Northwestern team dissolved the samples and analyzed their calcium isotope composition using a thermal ionization mass spectrometer. "The work is very challenging," Jacobson said. "To manipulate these tiny materials, you have to pick them up, one by one, with a wet paintbrush tip under a microscope."
Stress prior to PETM "We are looking at one group of organisms that built their shells in one part of the ocean, recording the seawater chemistry surrounding them," Kitch said. "We think the calcium isotope data reveal potential stress prior to the well-known boundary." Other archives indicate that the atmosphere-ocean system experienced a massive carbon dioxide release immediately before the PETM. When atmospheric carbon dioxide dissolves in seawater, it forms a weak acid that can inhibit calcium carbonate formation. Although it is still undetermined, Earth scientists believe the carbon release most likely came from volcanic activity or cascading effects, such as a release of methane hydrates from the seafloor as a result of ocean warming. "My suspicion is that it's both of these factors or some sort of combination," Sageman said. "Most big events in Earth's history represent a confluence of many actors coming together at the same time."
Consistent pattern emerges In all three studies, Jacobson's team used sophisticated tools in his laboratory to analyze the calcium isotope composition of calcium carbonate fossils and sediment. Jacobson said a clear pattern is emerging. Influxes of carbon dioxide led to global warming and ocean acidification and, ultimately, to massive environmental changes. "In all of our studies, we consistently see an increase in calcium isotope ratios before the onset of major events or extinction horizons," Jacobson said. "This seems to point to similar drivers and common responses." "Perhaps the calcium isotope system has a sensitivity to the earliest phases of these events," Sageman added.
Predictor for future ocean stress Frighteningly, terrestrial and ocean stress, including a major decrease in foraminiferal calcification, accompanied the PETM. "The PETM is a model for what happens during major large carbon cycle perturbations," Jacobson said. "A lot of predictions for Earth's future climate rely on understanding what happened during the PETM."
Research Report: "Calcium isotope composition of Morozovella over the Late Paleocene-early Eocene"
Pyrite isn't a reliable proxy for Earth's oxygenation, study says Washington DC (UPI) Feb 26, 2021 When did Earth first acquire large amounts of oxygen? What did the planet's earliest microbial communities look like? Many of the secrets of primordial Earth - its climate conditions and biochemical composition - are hidden in layers of marine sediments. To reconstruct Earth's past, scientists rely on certain chemical signatures preserved in the grains of sedimentary rocks. Now, new research suggests at least one of those signatures, a mineral called pyrite, is unreliable as a proxy fo ... read more
|
|
The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us. |