Carbon cycle – Page 2

July 1, 2021July 1, 2021

Buried treasure in the oceans: chemistry of small deep-sea crystals hints at past carbon cycling

Featured image: Crystals of the mineral barite from the deep ocean (Adapted from Kastner (1999)). These crystals precipitated in ocean sediments and are about 9 million years old, similar in age to some of the barite samples from the study discussed here.

Paper: A 35-million-year record of seawater stable Sr isotopes reveals a fluctuating global carbon cycle

Authors: Adina Paytan, Elizabeth M. Griffith, Anton Eisenhauer, Mathis P. Hain, Klaus Wallmann, Andrew Ridgwell

What do ancient ocean sediments and the walls around x-ray machines have in common? One possible answer? Sometimes the mineral barite is an important part of both! Barite (or barium sulfate) is able to block gamma and x-ray emissions, and therefore is sometimes used in high-density concrete in hospitals and laboratories. In the deep ocean, tiny crystals of barite naturally accumulate on the seafloor over time, particularly in regions ideal for this mineral formation where many decaying remains of organisms sink to the seafloor. The chemistry of this barite can give scientists clues into Earth’s past, which is what Adina Paytan and her colleagues did in this study.

June 24, 2021June 24, 2021

Microbes, tectonics, and the global carbon cycle

Featured image: Steam rising from a pool in the Aguas Termales area near the base of Rincón de la Vieja volcano in Costa Rica. Courtesy of the Global Volcanism Program, Smithsonian Institution; photo by Paul Kimberly.

Paper: Effect of tectonic processes on biosphere-geosphere feedbacks across a convergent margin
Authors: K. M. Fullerton, M. O. Schrenk, M. Yucel, E. Manini, M. Basili, T. J. Rogers, D. Fattorini, M. Di Carlo, G. d’Errico, F. Regoli, M. Nakagawa, C. Vetriani, F. Smedile, C. Ramirez, H. Miller, S. M. Morrison, J. Buongiorno, G. L. Jessen, A. D. Steen, M. Martinez, J. M. de Moor, P. H. Barry, D. Giovannelli, and K. G. Lloyd

Plate tectonics describes the workings of our planet on the gigantic scale of continents and oceans, moving graduallly over hundreds of millions of years. But the tectonic processes that slowly shape and reshape the whole surface of the Earth also directly influence the lives of some of our planet’s tiniest residents: microbes. And those microbes, in turn, may have a larger effect on Earth’s carbon cycle than previously estimated.

June 10, 2021June 14, 2021

The future cost of mercury exposure

Featured image: Rice paddy fields in Indonesia by Steve Douglas on Unsplash

Paper: Zhang, Y., Song, Z., Huang, S. et al. Global health effects of future atmospheric mercury emissions. Nat Commun 12, 3035 (2021). https://doi.org/10.1038/s41467-021-23391-7

Methylmercury, the organic form of the element mercury, is everywhere. A common global pollutant, this form of mercury is most commonly consumed by humans in food, and subsequent impacts include heart failure and loss of IQ. Environmental mercury is nothing short of a public health crisis, and while global interventions are rolling out to protect humans from this toxic pollutant, new research published in Nature Communications is showing us that the damage isn’t just in human lives, it’s also in dollars and cents.

February 9, 2021February 9, 2021

Tiny organisms’ race to the bottom of the ocean

Paper: Microbial dynamics of elevated carbon flux in the open ocean’s abyss

Authors: Kirsten Poff, Andy Leu, John Eppley, David Karl and Edward DeLong

Cells from blooms of phytoplankton, or tiny plants, can enhance carbon flux all the way down to the deepest parts of the ocean. The authors of this recent study measured the amount of carbon in sinking particles deep in the ocean at a station near Hawaii. Over the course of three years, scientists identified three time periods of unusually high carbon flux, or transport, at this depth, and found that the organisms that made up the sinking particles were significantly different between high flux events and the rest of the time period. The data showed higher abundances of surface-dwelling microorganisms, including phytoplankton, contributing to these particles during high-flux events.

February 4, 2021February 4, 2021

Cohesive trends in carbon cycling over the last 66 million years

Paper: Reconciling atmospheric CO₂, weathering, and calcite compensation depth across the Cenozoic

Featured image: Figure 1 from a related study: Boudreau et al., 2018 – a schematic which illustrates the carbonate/calcite compensation depth (CCD). Just as snow accumulates on mountains above the snowline and melts at lower elevations, white calcium carbonate shells and minerals (the sinking green discs in this image) accumulate on the seafloor above the CCD and dissolve below this depth.

Authors: Nemanja Komar and Richard E. Zeebe

For multiple decades, we have known that temperatures have largely cooled over the last 66 million years (during the Cenozoic, our current geological era). This insight comes from measuring oxygen isotopes in microfossil shells from ocean sediment cores that extend hundreds of meters into the deep ocean seafloor. Slight increases in the heavier oxygen isotope (which contains ten neutrons) relative to the lighter isotope (which contains eight neutrons) in these shells over time indicates cooling. However, it has been significantly more difficult to understand how the long-term geological carbon cycle has been intertwined with this temperature change. Since carbon and climate are inherently connected under modern and projected future climate change, it is crucial to understand these linkages. A new study by Komar and Zeebe expands a multi-faceted geological carbon and climate model to show how geological and geochemical evidence from ocean sediments that initially appears to be incompatible actually tells a cohesive story of carbon cycling and changes over the Cenozoic.

January 14, 2021January 14, 2021

It’s complicated; deciphering mixed signals of the carbon-climate relationship in Earth’s past

Paper: High-latitude biomes and rock weathering mediate climate-carbon cycle feedbacks on eccentricity timescales.

Authors: David De Vleeschower, Anna Joy Drury, Maximilian Vahlenkamp, Fiona Rochholz, Diederik Liebrand & Heiko Pälike

Featured image: Benthic foraminifera collected from the North Sea in 2011. Image courtesy of Hans Hillewaert, licensed under CC BY-SA 4.0

Faced with a rapidly warming world, we all have the same questions on our collective minds: how will climate change restructure Earth and what can we do to adapt to those changes? One thing we do know is that the climate is intimately connected to the carbon cycle. When large amounts of carbon get moved between reservoirs (on land and in the ocean and atmosphere), changes in climate ensue. Currently, carbon stored on land is being moved to the atmosphere through anthropogenic CO₂ emissions, causing global warming and its various cascading effects. What’s more, looking back in Earth’s history, researchers have established that moving carbon from the atmosphere to the ocean, or back onto land, has had a cooling effect. Just this past year, researchers from the University of Southampton investigated several factors affecting past carbon-climate connections, offering new understandings that could help address climate action moving forward.

January 12, 2021January 13, 2021

Muddy waters lead to decreased oxygen in Chesapeake Bay

Featured Image: Plumes of muddy, sediment-laden water at the Chesapeake Bay Bridge near Annapolis, MD. Photo courtesy of Jane Thomas/ IAN, UMCES.

Paper: Seabed Resuspension in the Chesapeake Bay: Implications for Biogeochemical Cycling and Hypoxia
Authors: Julia Moriarty, Marjorie Friedrichs, Courtney Harris

A memorable feature of the Chesapeake Bay, the largest estuary in the USA, is that the water is very murky and looks like chocolate milk. Former Senator Bernie Fowler has conducted public “wade-ins” over the past 50 years in one of the Bay’s tributaries, seeing how deep the water is before he can no longer see his white tennis shoes, and let’s just say it is never very deep. This is because of the high concentrations of sediment, or small particles of sand and organic material, in the water. Besides making it harder for seagrasses to grow and serving as food for the economically-important oyster, sediment impacts the biological processes that determine how much oxygen and nutrients are available in the water for algae and fish.

December 8, 2020December 9, 2020

The role of carbon in a changing Arctic

Paper: Freshening of the western Arctic negates anthropogenic carbon uptake potential

Authors: R.J. Woosley and F.J. Millero

Journal: Limnology and Oceanography

As human generated emissions of carbon dioxide continue to increase, scientists seek to understand the potential for ‘sinks’, or places that the excess CO₂ can move in the global carbon cycle, to take up and store some of the increased emissions. Understanding how these carbon sinks may react to increasing global emissions helps to better predict both the rate of atmospheric increase in the future and the potential response of global ecosystems, including major sinks in forests and oceans.

October 22, 2020October 26, 2020

Isotopes Begin to Unlock the Mystery of Methane Source in the Scheldt Estuary

Scheldt Estuary with tidal flats and water shown

Featured Image: Eastern Scheldt Estuary near Zeeland, Netherlands. Photo courtesy Wikimedia Commons/ Luka Peternel, CC BY-SA 4.0 license.

Paper: Carbon and Hydrogen Isotope Signatures of Dissolved Methane in the Scheldt Estuary

Authors: Caroline Jacques, Thanos Gkritzalis, Jean-Louis Tison, Thomas Hartley, Carina van der Veen, Thomas Röckmann, Jack J. Middelburg, André Cattrijsse, Matthias Egger, Frank Dehairs & Célia J. Sapart

Estuaries are dynamic coastal environments where freshwater and saltwater collide and mix. Across the world, estuaries regularly have higher methane concentrations in the water than would be expected from equilibrium with the atmosphere. If the water was in equilibrium, or at a happy balance, with the atmosphere, then there would be no net transfer of methane to the atmosphere. Because there is more methane than expected in the water, estuaries are a source of this potent greenhouse gas, methane (CH₄), to the atmosphere. The problem is that the processes leading to the excess methane in the estuary’s surface water are not well known in many European estuaries.

September 18, 2020September 18, 2020

New 23 million year record of atmospheric carbon dioxide highlights current human influence on the atmosphere

Paper: A 23 m.y. record of low atmospheric CO2

Featured image: Modern vascular land plants (Raphanus sativus), growing in a carbon dioxide experiment (Figure 1A from Jahren et al., 2008)

Authors: Ying Cui, Brian A. Schubert, A. Hope Jahren

Carbon dioxide is a greenhouse gas, trapping warmth within the Earth’s atmosphere. Sixty years of measurements on Hawaii’s Mauna Loa summit have shown rising amounts of carbon dioxide in our atmosphere. In addition, the carbon dioxide levels in our modern atmosphere are significantly higher than those we have seen on Earth over the last 800,000 years, according to measurements on bubbles of ancient air trapped in Antarctic ice. When combined with measurements of global temperatures, these direct measurements are irrefutable evidence for rapid modern climate change. However, understanding our current position relative to Earth’s climate farther back in time is trickier, since scientists have to estimate atmospheric composition indirectly (through a “proxy”). A new study tackles this problem with a new method of estimating past carbon dioxide, showing that modern carbon dioxide levels have been unprecedented since at least 7 million years ago.