Atmospheric composition 1 million years ago from blue ice in the Allan Hills, Antarctica

Higgins, John A.; Kurbatov, Andrei V.; Spaulding, Nicole; Brook, E.; Introne, D.; Chimiak, Laura; Yan, Yuzhen; Mayewski, Paul Andrew; Bender, Michael L.

doi:10.1073/pnas.1420232112

Cited by 147 publications

(135 citation statements)

References 29 publications

(36 reference statements)

Supporting

Mentioning

121

Contrasting

Unclassified

Order By: Relevance

“…Our analysis suggests that present-day glacial weathering causes net CO 2 release, but measurements from ice cores show no long-term change in mean atmospheric pCO 2 averaged over multiple glacial cycles during the past 1 My (52,53). Highly responsive global silicate weathering feedbacks could provide one mechanism explaining constant pCO 2 (54).…”

Section: Discussionmentioning

confidence: 78%

Glacial weathering, sulfide oxidation, and global carbon cycle feedbacks

Torres

Moosdorf

Hartmann

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

147

171

View full text Add to dashboard Cite

Connections between glaciation, chemical weathering, and the global carbon cycle could steer the evolution of global climate over geologic time, but even the directionality of feedbacks in this system remain to be resolved. Here, we assemble a compilation of hydrochemical data from glacierized catchments, use this data to evaluate the dominant chemical reactions associated with glacial weathering, and explore the implications for long-term geochemical cycles. Weathering yields from catchments in our compilation are higher than the global average, which results, in part, from higher runoff in glaciated catchments. Our analysis supports the theory that glacial weathering is characterized predominantly by weathering of trace sulfide and carbonate minerals. To evaluate the effects of glacial weathering on atmospheric pCO 2 , we use a solute mixing model to predict the ratio of alkalinity to dissolved inorganic carbon (DIC) generated by weathering reactions. Compared with nonglacial weathering, glacial weathering is more likely to yield alkalinity/DIC ratios less than 1, suggesting that enhanced sulfide oxidation as a result of glaciation may act as a source of CO 2 to the atmosphere. Back-of-the-envelope calculations indicate that oxidative fluxes could change ocean-atmosphere CO 2 equilibrium by 25 ppm or more over 10 ky. Over longer timescales, CO 2 release could act as a negative feedback, limiting progress of glaciation, dependent on lithology and the concentration of atmospheric O 2 . Future work on glaciation-weathering-carbon cycle feedbacks should consider weathering of trace sulfide minerals in addition to silicate minerals.weathering | carbon cycle | glaciation | oxidation | sulfide E pisodes of glaciation represent some of the most dramatic changes in the history of Earth's climate. Basic questions remain unanswered about why the planet has occasionally but not always supported glaciers, about why some glaciations have been more intense than others, and about how glaciers have shaped Earth's landscapes, chemical cycles, and climate. Before the Phanerozoic (i.e., before ∼540 Mya), several glaciations are thought to have approached complete or near-complete planetary ice cover ("Snowball Earth" events; ref. 1). In contrast, more recent glaciations, including the Quaternary glaciations of the last million years, have been characterized by oscillating climate with ice extent limited to high latitudes even during glacial maxima (2). The formation of ice cover has long been known to fundamentally alter Earth's environment, changing albedo (3), influencing atmospheric and ocean circulation (4), and reshaping landscapes (5). These diverse effects may contribute to planetary-scale feedbacks that influence the transition to and the evolution of glaciation.Chemical weathering influences the composition of the atmosphere by releasing ionic species from minerals that alter the alkalinity and redox condition of the ocean-atmosphere system. Weathering of silicate minerals produces alkalinity, removing carbon from the at...

show abstract

Section: Discussionmentioning

confidence: 78%

Glacial weathering, sulfide oxidation, and global carbon cycle feedbacks

Torres

Moosdorf

Hartmann

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

147

171

View full text Add to dashboard Cite

show abstract

“…In Antarctica, this includes sites at Scharffenbergbotnen (Sinisalo et al, 2007), Allan Hills (Spaulding et al, 2013), Mount Moulton (Custer, 2006;Korotkikh et al, 2011), Yamato Mountain (Moore et al, 2006), Taylor Glacier (Aciego et al, 2007), and Patriot Hills (Turney et al, 2013;Fogwill et al, 2017). Depending on the initial accumulation rate and the ice dynamics at a specific site, such records can span anywhere from a few thousand years at Yamato Mountain to 1 million years at Allan Hills (Higgins et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Atmospheric gas records from Taylor Glacier, Antarctica, reveal ancient ice with ages spanning the entire last glacial cycle

et al. 2017

View full text Add to dashboard Cite

Abstract.Old ice for paleo-environmental studies, traditionally accessed through deep core drilling on domes and ridges on the large ice sheets, can also be retrieved at the surface from ice sheet margins and blue ice areas. The practically unlimited amount of ice available at these sites satisfies a need in the community for studies of trace components requiring large sample volumes. For margin sites to be useful as ancient ice archives, the ice stratigraphy needs to be understood and age models need to be established. We present measurements of trapped gases in ice from Taylor Glacier, Antarctica, to date the ice and assess the completeness of the stratigraphic section. Using δ 18 O of O 2 and methane concentrations, we unambiguously identify ice from the last glacial cycle, covering every climate interval from the early Holocene to the penultimate interglacial. A high-resolution transect reveals the last deglaciation and the Last Glacial Maximum (LGM) in detail. We observe large-scale deformation in the form of folding, but individual stratigraphic layers do not appear to have undergone irregular thinning. Rather, it appears that the entire LGM-deglaciation sequence has been transported from the interior of the ice sheet to the surface of Taylor Glacier relatively undisturbed. We present an age model that builds the foundation for gas studies on Taylor Glacier. A comparison with the Taylor Dome ice core confirms that the section we studied on Taylor Glacier is better suited for paleo-climate reconstructions of the LGM due to higher accumulation rates.

show abstract

“…Re cently, Higgins et al . [11] reported on atmospher ic composition, including CO 2 , 1 million years ago from blue ice in the Allan Hills in Antarctica . The estimated 1 Ma ice, dated by the 40 Ar method with an uncertainty of about ±200 ka, was found in a stratigraphically disturbed section at the base of a 126 m ice core .…”

Section: Mpt and Atmospheric Comentioning

confidence: 99%

The Mid-Pleistocene Transition and the Vostok Oldest Ice Challenge

Lipenkov¹

2015

Lëd i sneg

View full text Add to dashboard Cite

Atmospheric composition 1 million years ago from blue ice in the Allan Hills, Antarctica

Cited by 147 publications

References 29 publications

Glacial weathering, sulfide oxidation, and global carbon cycle feedbacks

Glacial weathering, sulfide oxidation, and global carbon cycle feedbacks

Atmospheric gas records from Taylor Glacier, Antarctica, reveal ancient ice with ages spanning the entire last glacial cycle

The Mid-Pleistocene Transition and the Vostok Oldest Ice Challenge

Contact Info

Product

Resources

About