Heavy Noble Gas Isotopes as New Constraints on the Ventilation of the Deep Ocean

Seltzer, Alan M.; Pavia, F. J.; Ng, Jessica; Severinghaus, Jeffrey P.

doi:10.1029/2019gl084089

Cited by 9 publications

(29 citation statements)

References 37 publications

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“…To obtain them, we mathematically combine δXe/Ar, δKr/Ar, and δAr/N 2 . Ar itself is not used as a reference element because argon is preferentially excluded relative to N 2 , xenon, and krypton during bubble formation at the firn-ice transition (Severinghaus and Battle, 2006). The uncertainties calculated by error propagation of the analytical errors in the elemental ratios used in this calculation are 0.136 ‰ and 0.181 ‰ for δKr/N 2 and δXe/N 2 , respectively.…”

Section: Determination Of Noble Gas Elemental and Isotopic Ratios In Ice Coresmentioning

confidence: 99%

Snapshots of mean ocean temperature over the last 700 000 years using noble gases in the EPICA Dome C ice core

et al. 2021

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Abstract. Together with the latent heat stored in glacial ice sheets, the ocean heat uptake carries the lion's share of glacial–interglacial changes in the planetary heat content, but little direct information on the global mean ocean temperature (MOT) is available to constrain the ocean temperature response to glacial–interglacial climate perturbations. Using ratios of noble gases and molecular nitrogen trapped in the Antarctic EPICA Dome C ice core, we are able to reconstruct MOT for peak glacial and interglacial conditions during the last 700 000 years and explore the differences between these extrema. To this end, we have to correct the noble gas ratios for gas transport effects in the firn column and gas loss fractionation processes of the samples after ice core retrieval using the full elemental matrix of N2, Ar, Kr, and Xe in the ice and their individual isotopic ratios. The reconstructed MOT in peak glacials is consistently about 3.3 ± 0.4 ∘C cooler compared to the Holocene. Lukewarm interglacials before the Mid-Brunhes Event 450 kyr ago are characterized by 1.6 ± 0.4 ∘C lower MOT than the Holocene; thus, glacial–interglacial amplitudes were only about 50 % of those after the Mid-Brunhes Event, in line with the reduced radiative forcing by lower greenhouse gas concentrations and their Earth system feedbacks. Moreover, we find significantly increased MOTs at the onset of Marine Isotope Stage 5.5 and 9.3, which are coeval with CO2 and CH4 overshoots at that time. We link these CO2 and CH4 overshoots to a resumption of the Atlantic Meridional Overturning Circulation, which is also the starting point of the release of heat previously accumulated in the ocean during times of reduced overturning.

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Section: Determination Of Noble Gas Elemental and Isotopic Ratios In Ice Coresmentioning

confidence: 99%

Snapshots of mean ocean temperature over the last 700 000 years using noble gases in the EPICA Dome C ice core

et al. 2021

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“…Note that we assume ocean solubility effects on the isotopic ratios to be negligible (in contrast to the elemental ratios, where we use these effects to quantify MOT). This can be justified using a two-box model calculation with the recently determined solubility fractionation factors in seawater (Seltzer et al, 2019) and imposed ocean temperature differences, which yields glacial/interglacial changes in atmospheric noble gas isotope composition of less than 0.001‰ per unit mass difference. We can, thus, safely assume that for isotopic ratios δ * atm = 0 (where for Ar isotopes the atmospheric value has to be corrected for Ar outgassing as described in 2.2.1).…”

Section: Correcting Isotopic Ratios For Transport Processes In the Fimentioning

confidence: 99%

Snapshots of mean ocean temperature over the last 700,000 yr using noble gases in the EPICA Dome C ice core

Haeberli¹,

Baggenstos²,

Schmitt³

et al. 2020

Preprint

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Abstract. Together with the latent heat stored in glacial ice sheets the ocean heat uptake carries the lion’s share of glacial/interglacial changes in the planetary heat content but little direct information on the global mean ocean temperature (MOT) is available to constrain the ocean temperature response to glacial/interglacial climate perturbations. Using ratios of noble gases and molecular nitrogen trapped in the Antarctic EPICA Dome C ice core we are able to reconstruct MOT for peak glacial and interglacial conditions during the last 700,000 years and explore the differences between these extrema. To this end, we have to correct the noble gas ratios for gas transport effects in the firn column and gas loss fractionation processes of the samples after ice core retrieval using the full elemental matrix of N2, Ar, Kr and Xe in the ice and their individual isotopic ratios. The reconstructed MOT in peak glacials is consistently about 3.3 ± 0.4 °C cooler compared to the Holocene. Lukewarm interglacials before the Mid Brunhes event 450 kyr ago are characterized by 1.6 ± 0.4 °C lower temperatures in the ocean than the Holocene, thus, glacial/interglacial amplitudes were only about 50 % of those after the Mid Brunhes event, in line with the reduced radiative forcing by lower greenhouse gas concentrations and their Earth system feedbacks. Moreover, we find significantly increased MOTs at the onset of Marine Isotope Stage 5.5 and 9.3, which are coeval with CO2 and CH4 overshoots at that time. We link these CO2 and CH4 overshoots to a resumption of the Atlantic Meridional Overturning Circulation, which is also the starting point of the release of heat previously accumulated in the ocean during times of reduced overturning.

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“…High‐precision measurements of triple Ar isotopes used to quantify radiogenic 40 Ar content in groundwater additionally serve as a new tracer of groundwater age, rock composition, and rock weatherability 11 . In seawater, dissolved Kr and Xe isotopes offer promising new constraints on ventilation processes that contribute to observed deep ocean inert gas disequilibria 5,12 …”

Section: Introductionmentioning

confidence: 99%

“…11 In seawater, dissolved Kr and Xe isotopes offer promising new constraints on ventilation processes that contribute to observed deep ocean inert gas disequilibria. 5,12 Previous high-precision noble gas methods involved collecting water samples in 2-L glass flasks, quantitatively extracting dissolved gases via sparging with He as a carrier gas, and measuring isotopic and elemental ratios on a dynamic isotope ratio mass spectrometer (IRMS). 13 We refer to this technique here as the large-volume sparging (LVS) method.…”

mentioning

confidence: 99%

A new large‐volume equilibration method for high‐precision measurements of dissolved noble gas stable isotopes

Tyne

Seltzer

et al. 2023

Rapid Comm Mass Spectrometry

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Rationale: Noble gases are widely used as physically based climate proxies, notably in dissolved water samples as tracers of past recharge temperature in groundwater and air-sea gas exchange processes in seawater. Recent advances in measuring largevolume samples of dissolved noble gas isotopic ratios at high precision have expanded the range of climate parameters that can be interpreted. Methods:We build on prior methods for measuring noble gas stable isotopes at high precision with a new large-volume equilibration (LVE) method wherein sample gases are equilibrated in the sample flask between the dissolved phase and the headspace.The original dissolved gas composition is determined by measuring the headspace gases and correcting for the equilibrium dissolved gas content of the discarded water using known solubilities and fractionation factors. We evaluate the accuracy and precision of this method with air-equilibrated water standards of known noble gas composition.Results: Replicate air-equilibrated water standards and field measurements demonstrate that the LVE method achieves comparable precision to prior methods, with major advantages of measuring the Ne content as a constraint on excess air and allowing for long-term sample storage. Isotope ratios measured with the LVE method in replicate samples were consistent between two laboratories, and LVE elemental noble gas abundances agreed closely with replicate samples measured using established copper-tube methods and static noble gas mass spectrometry. Conclusions:The new LVE method enables reconstruction of past water table depths at ±1 m precision along with excess air, recharge temperature, and age and hydrogeochemical indicators. It has wide application to investigating climate signals and physical gas exchange processes in groundwater and seawater. | INTRODUCTIONNoble gases are valuable physical tracers of past climate and gas exchange processes due to their chemical and biological inertness, and their presence in various terrestrial, marine, and polar climate archives. In groundwater and ice cores, noble gases are a wellestablished tool to reconstruct paleotemperatures at the time of recharge or air-bubble closure in ice based on their temperaturedependent solubilities. [1][2][3] In seawater, noble gas measurements help distinguish physical processes of air-sea gas exchange from biogeochemical ones. 4,5 Dissolved noble gases in groundwater or seawater are typically sampled in 10-50-ml copper tubes for measurement of elemental abundances via static mass spectrometry (herein, the CT method). 6 Recently, high-precision measurements of dissolved argon (Ar), krypton (Kr), and xenon (Xe) stable isotope ratios-alongside their elemental concentrations-have allowed for reconstructions of additional paleoclimatic parameters beyond traditional

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Heavy Noble Gas Isotopes as New Constraints on the Ventilation of the Deep Ocean

Cited by 9 publications

References 37 publications

Snapshots of mean ocean temperature over the last 700 000 years using noble gases in the EPICA Dome C ice core

Snapshots of mean ocean temperature over the last 700 000 years using noble gases in the EPICA Dome C ice core

Snapshots of mean ocean temperature over the last 700,000 yr using noble gases in the EPICA Dome C ice core

A new large‐volume equilibration method for high‐precision measurements of dissolved noble gas stable isotopes

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