Climatic and insolation control on the high-resolution total air content in the NGRIP ice core

Eicher, O.; Baumgartner, M.; Schilt, A.; Schmitt, Jochen; Schwander, Jakob; Stocker, Thomas F.; Fischer, Hubertus

doi:10.5194/cpd-11-5509-2015

Cited by 6 publications

(7 citation statements)

References 42 publications

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“…This correlation indicates that the bubble air was squeezed out before close-off, resulting in smaller air contents when overloading pressure was higher, eventually inducing higher pressure in the bubbles and thus enhanced δAr/N 2 depletions. This observation is also consistent with recent findings that abrupt increases of accumulation rate at abrupt warming during the last glacial period induced reductions in air contents (Eicher et al, 2015). In addition, artificial sintering of snow with higher pressure has been shown to contain much smaller air content than ice cores, owing to the lack of time to develop spherical cavities by vapor transport (B. Stauffer, personal communication, 2015).…”

Section: Total Air In Bubblessupporting

confidence: 80%

Post-bubble close-off fractionation of gases in polar firn and ice cores: effects of accumulation rate on permeation through overloading pressure

et al. 2015

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Abstract. Gases in ice cores are invaluable archives of past environmental changes (e.g., the past atmosphere). However, gas fractionation processes after bubble closure in the firn are poorly understood, although increasing evidence indicates preferential leakages of smaller molecules (e.g., neon, oxygen, and argon) from the closed bubbles through the ice matrix. These fractionation processes are believed to be responsible for the observed millennial δO 2

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Section: Total Air In Bubblessupporting

confidence: 80%

Post-bubble close-off fractionation of gases in polar firn and ice cores: effects of accumulation rate on permeation through overloading pressure

et al. 2015

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“…Reversing the approach, one can calculate atmospheric pressure during gas trapping from temperature (δ 18 O ice ), the empirical relationship between close-off volume and temperature, and the ideal gas law. In addition, Raynaud et al (7) and others (26,27) identified a link between total air content and local summertime insolation. Accounting for this link, NEEM et al (6) quantified the effect of insolation and estimated that, during the Eemian, elevation at NEEM was within a few hundred meters of the present elevation.…”

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confidence: 98%

Reconstructing the last interglacial at Summit, Greenland: Insights from GISP2

Yau

Bender

Robinson

et al. 2016

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

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The Eemian (last interglacial, 130-115 ka) was likely the warmest of all interglacials of the last 800 ka, with summer Arctic temperatures 3-5°C above present. Here, we present improved Eemian climate records from central Greenland, reconstructed from the base of the Greenland Ice Sheet Project 2 (GISP2) ice core. Our record comes from clean, stratigraphically disturbed, and isotopically warm ice from 2,750 to 3,040 m depth. N of N 2 , and total air content for samples dating discontinuously from 128 to 115 ka indicate a warming of ∼6°C between 127-121 ka, and a similar elevation history between GISP2 and NEEM. The reconstructed climate and elevation histories are compared with an ensemble of coupled climate-ice-sheet model simulations of the Greenland ice sheet. Those most consistent with the reconstructed temperatures indicate that the Greenland ice sheet contributed 5.1 m (4.1-6.2 m, 95% credible interval) to global eustatic sea level toward the end of the Eemian. Greenland likely did not contribute to anomalously high sea levels at ∼127 ka, or to a rapid jump in sea level at ∼120 ka. However, several unexplained discrepancies remain between the inferred and simulated histories of temperature and accumulation rate at GISP2 and NEEM, as well as between the climatic reconstructions themselves.Greenland ice sheet | last interglacial | ice cores | sea level rise D uring the last interglacial (Eemian, 130-115 ka), Arctic summer temperatures were 3-5°C warmer than today (1), and peak global eustatic sea level was likely 6-9 m higher than the present (2). In the next century, due to anthropogenic emissions of greenhouse gases, we face a similar temperature scenario with 2-6°C of northern hemispheric polar warming (3), and a likely initial sea level rise (by 2100) of 0.3-1.0 m (4), with higher, but uncertain, levels beyond. Certainly there are important differences between the warming and sea level change observed during the last climatic warm period and future projections, notably the rate at which warming is expected to occur and its spatial pattern. Nevertheless, the Eemian history of the Greenland ice sheet (GrIS) serves as an essential test bed for understanding changes in ice sheets and sea level rise in response to rising global temperatures.Ice sheet modeling studies have estimated a wide range of GrIS contributions to sea level during the Eemian, with simulations producing 0.4-5.5 m of equivalent sea level rise above the present datum (5).

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“…Freitag, personal communication, 2016) but also by daily weather events. Hutterli et al (2009) state that the total temperature gradient metamorphism (tTGM) influences the physical properties of the snowpack. tTGM is not necessarily synchronous with insolation, leading to a lag between the orbital parameters and the proxies depending on snow structure.…”

Section: Introductionmentioning

confidence: 99%

Climatic and insolation control on the high-resolution total air content in the NGRIP ice core

et al. 2016

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Abstract. Because the total air content (TAC) of polar ice is directly affected by the atmospheric pressure and temperature, its record in polar ice cores was initially considered as a proxy for past ice sheet elevation changes. However, the Antarctic ice core TAC record is known to also contain an insolation signature, although the underlying physical mechanisms are still a matter of debate. Here we present a highresolution TAC record over the whole North Greenland Ice Core Project ice core, covering the last 120 000 years, which independently supports an insolation signature in Greenland. Wavelet analysis reveals a clear precession and obliquity signal similar to previous findings on Antarctic TAC, with a different insolation history. In our high-resolution record we also find a decrease of 4-6 % (4-5 mL kg −1 ) in TAC as a response to Dansgaard-Oeschger events (DO events). TAC starts to decrease in parallel to increasing Greenland surface temperature and slightly before CH 4 reacts to the warming but also shows a two-step decline that lasts for several centuries into the warm interstadial. The TAC response is larger than expected considering only changes in air density by local temperature and atmospheric pressure as a driver, pointing to a transient firnification response caused by the accumulation-induced increase in the load on the firn at bubble close-off, while temperature changes deeper in the firn are still small.

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Climatic and insolation control on the high-resolution total air content in the NGRIP ice core

Cited by 6 publications

References 42 publications

Post-bubble close-off fractionation of gases in polar firn and ice cores: effects of accumulation rate on permeation through overloading pressure

Post-bubble close-off fractionation of gases in polar firn and ice cores: effects of accumulation rate on permeation through overloading pressure

Reconstructing the last interglacial at Summit, Greenland: Insights from GISP2

Climatic and insolation control on the high-resolution total air content in the NGRIP ice core

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