The Impact of Nonequilibrium and Equilibrium Fractionation on Two Different Deuterium Excess Definitions

Dütsch, Marina; Sodemann, Harald

doi:10.1002/2017jd027085

Cited by 39 publications

(52 citation statements)

References 60 publications

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“…This conservation property is not generally valid (Petit et al ., ; Masson‐Delmotte et al ., ). Additional factors such as cloud microphysical processes as well as the d definition problem (Dütsch et al ., ; Markle et al ., ) can potentially alter the above‐described moisture source isotope–climate relationship at low absolute humidity levels in polar regions. But this property is used and justified in this study, because of the close distance of Reykjavik to its marine moisture source and moderate rain out states of the air parcels leading to precipitation at this location.…”

Section: Introductionmentioning

confidence: 99%

On the link between the North Atlantic storm track and precipitation deuterium excess in Reykjavik

Aemisegger

2018

Atmospheric Science Letters

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This study establishes a robust process-based dynamical link between the variability of the deuterium excess (d) in monthly winter precipitation in Reykjavik and the frequency of strong large-scale ocean evaporation (SLOE) events in the subpolar North Atlantic. SLOE events are induced by cold advection in the rear of extratropical cyclones. The link between SLOE and d emerges from the fact that a substantial fraction of moisture that precipitates in Reykjavik in winter originates from SLOE events. It is shown that positive anomalies of monthly d co-occur with positive anomalies in the frequency of SLOE events at the moisture source of Reykjavik precipitation. An intensification and a northeastwards shift of the North Atlantic storm track acts as a driver for the enhanced SLOE frequency in months with positive anomalies in d. This link also implies that in the subpolar North Atlantic, variations of d in monthly (or seasonal) precipitation reveal information about the storm track dynamics in the vicinity of Iceland. Potential implications of this finding for the interpretation of d as a proxy for the location and intensity of storm tracks are discussed. K E Y W O R D Satmospheric water cycle, extratropical cyclones, precipitation moisture sources, stable water isotopes, storm track dynamics, strong ocean evaporation

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Section: Introductionmentioning

confidence: 99%

On the link between the North Atlantic storm track and precipitation deuterium excess in Reykjavik

Aemisegger

2018

Atmospheric Science Letters

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“…Alternative definitions of d-excess using a logarithm formulation have thus been proposed to circumvent this site temperature signal (e.g. Uemura et al, 2012;Markle et al, 2016;Dütsch et al, 2017). However, the ln(D+1) vs ln( 18 O+1) slope is not as constant as the  18 O vs D slope for large  18 O -D ranges, hence leading to variable slope as a function of  18 O values when defining the excess with a logarithm definition.…”

Section: -Introductionmentioning

confidence: 99%

Unveiling the anatomy of Termination 3 using water and air isotopes in the Dome C ice core, East Antarctica

Bréant

Landais

Orsi

et al. 2019

Quaternary Science Reviews

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Each glacial-interglacial transition of the Quaternary occurs in a different orbital context leading to various timing for the deglaciation and sequence of high vs low latitudes events. Termination 3, 250 kiloyears before present (ka), is an unusual deglaciation in the context of the last 9 deglaciations recorded in the old EPICA Dome C (EDC) Antarctic ice core: it exhibits a three-phase sequence, two warming phases separated by a small cooling, the last phase suggesting a particularly rapid temperature increase. We present here new high resolution  15 N and deuterium excess (d-excess) data from the EDC ice core to provide a detailed temperature change estimate during this termination. Then, we combined the D and  18 O to discuss the relationship between high and low latitude changes through the d-excess. We also provide the high vs low latitude sequence of events over this deglaciation without chronological uncertainty using low latitude ice core proxies. In agreement with previous studies based on speleothem analyses, we show that the first phase of Termination 3 (256 to 249 ka) is associated with small Heinrich like events linked to changes in ITCZ position, monsoon activity and teleconnections with Antarctica. In a context of minimum Northern Hemisphere insolation, 2 this leads to a rather strong Antarctic warming, as observed in the  15 N record in contrast to the relatively small D increase. The second warming phase occurs during the rise of the Northern hemisphere insolation, with a large Heinrich like event leading to the characteristic Antarctic warming observed in the  15 N and D increase as for the more recent terminations.

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“…The increase of d v with height (e.g., Bony et al, 2008;Sodemann et al, 2017) and non-equilibrium effects during precipitation formation in mixed-phase clouds, both increase d p,eq (and ∆d). This increase is however counteracted by a decrease of d p,eq during the vapour-solid transition and by a decrease due to the non-linearity of the δ-scale (Dütsch et al, 2017). The preferential loss of light isotopes and non-equilibrium effects during evaporation of rain will increase δ 2 H p,eq (and ∆δ) 20 and decrease d p,eq (and ∆d).…”

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confidence: 95%

“…In equilibrium, there is no net exchange of molecules between the phases, i.e., the exchange in both directions is equal for all isotopic species. Temperature-dependent isotopic fractionation between light and heavy isotopes 25 however gives rise to different isotopic compositions of the liquid and vapour phases in equilibrium:…”

Section: Equilibrium Vapour From Precipitationmentioning

confidence: 99%

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A new interpretative framework for below-cloud effects on stable water isotopes in vapour and rain

Graf¹,

Wernli²,

Sodemann³

2018

Preprint

Self Cite

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Abstract. Raindrops interact with water vapour in ambient air while sedimenting from the cloud base to the ground. They constantly exchange water molecules with the environment and, in sub-saturated air, they evaporate partially or entirely. The latter of these below-cloud processes is important for predicting the resulting surface rainfall amount and it influences the boundary layer profiles of temperature and moisture through to evaporative latent cooling and humidity changes. However, despite its importance, it is very difficult to quantify this process from observations. Stable water isotopes provide such infor-5 mation, as they are influenced by both rain evaporation and equilibration. This study elucidates this option by introducing a novel interpretation framework for stable water isotope measurements performed simultaneously at high temporal resolution in both near-surface vapour and rain. We refer to this viewing device as the ∆δ∆d-diagram, which shows the isotopic composition (δ 2 H, d-excess) of equilibrium vapour from precipitation samples relative to the ambient vapour. It is shown that this diagram facilitates the diagnosis of below-cloud processes and their effects on the isotopic composition of vapour and rain 10 since equilibration and evaporation lead to different pathways in the two-dimensional phase space of the ∆δ∆d-diagram. For a specific cold front in Central Europe, the analysis shows that below-cloud processes lead to distinct and temporally variable imprints on the isotope signal in surface rain. The influence of evaporation on this signal is particularly strong during periods with a weak precipitation rate. After the frontal passage, the near-surface atmospheric layer is characterised by higher relative humidity and a lower melting layer, leading to weaker below-cloud evaporation and equilibration. Measurements from four 15 cold frontal events reveal a surprisingly similar slope of ∆d ∆δ = −0.30 in the phase space, indicating a potentially characteristic signature of below-cloud processes for this type of rain events.

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The Impact of Nonequilibrium and Equilibrium Fractionation on Two Different Deuterium Excess Definitions

Cited by 39 publications

References 60 publications

On the link between the North Atlantic storm track and precipitation deuterium excess in Reykjavik

On the link between the North Atlantic storm track and precipitation deuterium excess in Reykjavik

Unveiling the anatomy of Termination 3 using water and air isotopes in the Dome C ice core, East Antarctica

A new interpretative framework for below-cloud effects on stable water isotopes in vapour and rain

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