scholarly journals A Review of Antarctic Surface Snow Isotopic Composition: Observations, Atmospheric Circulation, and Isotopic Modeling*

2008 ◽  
Vol 21 (13) ◽  
pp. 3359-3387 ◽  
Author(s):  
V. Masson-Delmotte ◽  
S. Hou ◽  
A. Ekaykin ◽  
J. Jouzel ◽  
A. Aristarain ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
General Circulation ◽  
Deuterium Excess ◽  
Atmospheric Models ◽  
Moisture Advection ◽  
Spatial Coverage ◽  
Antarctic Snow ◽  
Local Variability ◽  
Geographical Characteristics

Abstract A database of surface Antarctic snow isotopic composition is constructed using available measurements, with an estimate of data quality and local variability. Although more than 1000 locations are documented, the spatial coverage remains uneven with a majority of sites located in specific areas of East Antarctica. The database is used to analyze the spatial variations in snow isotopic composition with respect to geographical characteristics (elevation, distance to the coast) and climatic features (temperature, accumulation) and with a focus on deuterium excess. The capacity of theoretical isotopic, regional, and general circulation atmospheric models (including “isotopic” models) to reproduce the observed features and assess the role of moisture advection in spatial deuterium excess fluctuations is analyzed.

scholarly journals The Isotopic Composition of Present-Day Antarctic Snow in a Lagrangian Atmospheric Simulation*

2007 ◽  
Vol 20 (4) ◽  
pp. 739-756 ◽  
Author(s):  
M. M. Helsen ◽  
R. S. W. Van de Wal ◽  
M. R. Van den Broeke
Keyword(s):  
Isotopic Composition ◽  
General Circulation ◽  
Isotopic Fractionation ◽  
General Circulation Models ◽  
Deuterium Excess ◽  
West Antarctica ◽  
Temperature Relation ◽  
Weather Forecasts ◽  
Spatial Differences ◽  
Antarctic Snow

Abstract The isotopic composition of present-day Antarctic snow is simulated for the period September 1980–August 2002 using a Rayleigh-type isotope distillation model in combination with backward trajectory calculations with 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) data as meteorological input. Observed spatial isotopic gradients are correctly reproduced, especially in West Antarctica and in the coastal areas. However, isotopic depletion of snow on the East Antarctic plateau is underestimated, a problem that is also observed in general circulation models equipped with isotope tracers. The spatial isotope–temperature relation varies strongly, which indicates that this widely used relation is not applicable to all sites and temporal scales. Spatial differences in the seasonal amplitude are identified, with maximum values in the Antarctic interior and hardly any seasonal isotope signature in Marie Byrd Land, West Antarctica. The modeled signature of deuterium excess remains largely preserved during the last phase of transport, though the simulated relation of deuterium excess with δ18O suggests that parameterizations of kinetic isotopic fractionation can be improved.

scholarly journals Three-year monitoring of stable isotopes of precipitation at Concordia Station, East Antarctica

2016 ◽  
Author(s):  
Barbara Stenni ◽  
Claudio Scarchilli ◽  
Valerie Masson-Delmotte ◽  
Elisabeth Schlosser ◽  
Virginia Ciardini ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Isotopic Composition ◽  
Air Temperature ◽  
General Circulation ◽  
Daily Precipitation ◽  
Circulation Model ◽  
Ice Cores ◽  
Condensation Temperature ◽  
Deuterium Excess ◽  
Medium Range Weather Forecast

Abstract. Past temperature reconstructions from Antarctic ice cores require a good quantification and understanding of the relationship between snow isotopic composition and 2&thninsp;m air or inversion (condensation) temperature. Here, we focus on the French-Italian Concordia Station, central East Antarctic plateau, where the European Project for Ice Coring in Antarctica (EPICA) Dome C ice cores were drilled. We provide a multi-year record of daily precipitation types identified from crystal morphologies, daily precipitation amounts, and isotopic composition. Our sampling period (2008–2010) encompasses a warmer year (2009, +1.6 °C with respect to 2&thninsp;m air temperature period average), with larger total precipitation and snowfall amounts (14 %, 76 % above average, respectively), and a colder and drier year (2010, −1.4 °C, 4 % below average, respectively) with larger diamond dust amounts (49 % above average). Relationships between local meteorological data and precipitation isotopic composition are investigated at daily, monthly and inter-annual scale, and for the different types of precipitation. Water stable isotopes are more closely related to 2 m air temperature than to inversion temperature at all time scales (e.g. R2 = 0.63 and 0.44, respectively for daily values). The slope of the temporal relationship between daily d18O and 2 m air temperature is approximately two times smaller (0.49 ‰/°C) than the average Antarctic spatial (0.8 ‰/°C) relationship initially used for the interpretation of EPICA Dome C records. In accordance to results from precipitation monitoring at Vostok and Dome F, deuterium excess is anti-correlated with δ18O at daily and monthly scales, reaching maximum values in winter. Hoar frost precipitation samples have a specific fingerprint with more depleted d18O (about 5 ‰ below average) and higher deuterium excess (about 8 ‰ above average) values than other precipitation types. These datasets provide a basis for comparison with shallow ice core records, to investigate post-deposition effects. A preliminary comparison between observations and precipitation from the European Centre for Medium-Range Weather Forecast (ECMWF) re-analysis and the simulated water stable isotopes from the Laboratoire de Météorologie Dynamique Zoom atmospheric general circulation model (LMDZiso), shows that models do correctly capture the amount of precipitation as well as more than 50 % of the variance of the observed δ18O, driven by large scale weather patterns. Despite a warm bias and an underestimation of the variance in water stable isotopes, LMDZiso correctly captures these relationships between δ18O, 2 m air temperature and deuterium excess. Our dataset is therefore available for further in depth model evaluation at the synoptic scale.

scholarly journals The isotopic composition of water vapour and precipitation in Ivittuut, Southern Greenland

2013 ◽  
Vol 13 (11) ◽  
pp. 30521-30574 ◽  
Author(s):  
J.-L. Bonne ◽  
V. Masson-Delmotte ◽  
O. Cattani ◽  
M. Delmotte ◽  
C. Risi ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Isotopic Composition ◽  
Water Vapour ◽  
Seasonal Variations ◽  
General Circulation ◽  
Deuterium Excess ◽  
Local Surface ◽  
Long Distance ◽  
Atlantic Sector ◽  
Moisture Sources

Abstract. Since September 2011, a Wavelength-Scanned Cavity Ringdown Spectroscopy analyzer has been remotely operated in Ivittuut, southern Greenland, providing the first continuous record of surface water vapour isotopic composition (δ18O, δD) in South Greenland and the first record including the winter season in Greenland. This record depicts small summer diurnal variations. Measurements of precipitation isotopic composition suggest equilibrium between surface vapour and precipitation. The vapour data show large synoptic and seasonal variations corresponding to shifts in moisture sources estimated using a quantitative moisture source diagnostic. The arrival of low pressure systems towards south Greenland leads to δ18O enrichment (+5‰) and deuterium excess depletion (−15‰), coupled with moisture sources shifts. Monthly δ18O is minimum in November–December and maximum in June–July, with a seasonal amplitude of ~10‰. The strong correlation between δ18O and the logarithm of local surface humidity is consistent with Rayleigh distillation processes. The relationship with local surface air temperature is associated with a slope of ~0.4‰ °C−1. During the summer 2012 heat waves, the observations display a divergence between δ18O and local climate variables, probably due to the isotopic depletion associated with long distance transport from subtropical moisture sources. Monthly deuterium excess is minimum in May–June and maximum in November, with a seasonal amplitude of 20‰. It is anti-correlated with δ18O, and correlated with local surface relative humidity (at the station) as well as surface relative humidity in a North Atlantic sector, south of Greenland and Iceland. While synoptic and seasonal variations are well represented by the Atmospheric General Circulation Model LMDZiso for Ivittuut δ18O, the model does not capture the magnitude of these variations for deuterium excess.

scholarly journals Microbiota entrapped in recently-formed ice: Paradana Ice Cave, Slovenia

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Janez Mulec ◽  
Andreea Oarga-Mulec ◽  
Ladislav Holko ◽  
Lejla Pašić ◽  
Andreja Nataša Kopitar ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Meteoric Water ◽  
Total Cell ◽  
Monthly Precipitation ◽  
Depth Gradient ◽  
Deuterium Excess ◽  
Ice Volume ◽  
The Core ◽  
Low Concentrations

AbstractParadana is one of the biggest ice caves in Slovenia, with an estimated ice volume of 8,000 m3. Reflecting climatological conditions, the cave ice undergoes repeated freeze-thaw cycles and regular yearly deposition of fresh ice. Three distinct ice block samples, collected from the frozen lake in May 2016, were analysed to obtain data on ice physicochemical properties and the composition of associated microbiota. Isotopic composition of the ice samples (18O, 2H) and a local meteoric water line (LMWL) constructed for monthly precipitation at Postojna were used to estimate the isotopic composition of the water that formed the ice, which had high values of deuterium excess and low concentrations of chloride, sulphate and nitrate. The values of total organic carbon (1.93–3.95 mg/l) within the ice blocks fall within the range of those measured in karst streams. Total cell count in the ice was high and the proportion of cell viability increased along the depth gradient and ranged from 4.67 × 104 to 1.52 × 105 cells/ml and from 51.0 to 85.4%, respectively. Proteobacteria represented the core of the cave-ice microbiome (55.9–79.1%), and probably play an essential role in this ecosystem. Actinobacteria was the second most abundant phylum (12.0–31.4%), followed in abundance by Bacteroidetes (2.8–4.3%). Ice phylotypes recorded amounted to 442 genera, but only 43 genera had abundances greater than 0.5%. Most abundant were Pseudomonas, a well-known ice dweller, and Lysobacter, which previously was not reported in this context. Finally, two xanthophytes, Chloridella glacialis and Ellipsoidion perminimum, known from polar environments, were cultured from the ice. This indicates that the abundance and ecological role of phototrophs in such environments might be greater than previously deduced.

scholarly journals Moisture Asymmetry and MJO Eastward Propagation in an Aquaplanet General Circulation Model*

2014 ◽  
Vol 27 (23) ◽  
pp. 8747-8760 ◽  
Author(s):  
Pang-Chi Hsu ◽  
Tim Li ◽  
Hiroyuki Murakami
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Circulation Model ◽  
Specific Humidity ◽  
Sensitivity Experiment ◽  
Moisture Advection ◽  
Dominant Period ◽  
Numerical Model Experiments ◽  
Humidity Field

Abstract The role of zonal moisture asymmetry in the eastward propagation of the Madden–Julian oscillation (MJO) is investigated through a set of aquaplanet atmospheric general circulation model (AGCM) experiments with a zonally symmetric sea surface temperature distribution. In the control experiment, the model produces eastward-propagating MJO-like perturbations with a dominant period of 30–90 days. The model MJO exhibits a clear zonal asymmetry in the lower-tropospheric specific humidity field, with a positive (negative) anomaly appearing to the east (west) of the MJO convection. A diagnosis of the lower-tropospheric moisture budget indicates that the asymmetry primarily arises from vertical moisture advection associated with boundary layer convergence, while horizontal moisture advection has the opposite effect. In a sensitivity experiment, the lower-tropospheric specific humidity field is relaxed toward a zonal-mean basic state derived from the control simulation. In this case, the model’s mean state remains the same, but its intraseasonal mode becomes quasi-stationary. The numerical model experiments clearly demonstrate the importance of the zonal moisture asymmetry in MJO eastward propagation.

scholarly journals Three-year monitoring of stable isotopes of precipitation at Concordia Station, East Antarctica

2016 ◽  
Vol 10 (5) ◽  
pp. 2415-2428 ◽  
Author(s):  
Barbara Stenni ◽  
Claudio Scarchilli ◽  
Valerie Masson-Delmotte ◽  
Elisabeth Schlosser ◽  
Virginia Ciardini ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Isotopic Composition ◽  
Air Temperature ◽  
General Circulation ◽  
Daily Precipitation ◽  
Ice Cores ◽  
Sampling Period ◽  
Condensation Temperature ◽  
Deuterium Excess

Abstract. Past temperature reconstructions from Antarctic ice cores require a good quantification and understanding of the relationship between snow isotopic composition and 2 m air or inversion (condensation) temperature. Here, we focus on the French–Italian Concordia Station, central East Antarctic plateau, where the European Project for Ice Coring in Antarctica (EPICA) Dome C ice cores were drilled. We provide a multi-year record of daily precipitation types identified from crystal morphologies, daily precipitation amounts and isotopic composition. Our sampling period (2008–2010) encompasses a warmer year (2009, +1.2 °C with respect to 2 m air temperature long-term average 1996–2010), with larger total precipitation and snowfall amounts (14 and 76 % above sampling period average, respectively), and a colder and drier year (2010, −1.8 °C, 4 % below long-term and sampling period averages, respectively) with larger diamond dust amounts (49 % above sampling period average). Relationships between local meteorological data and precipitation isotopic composition are investigated at daily, monthly and inter-annual scale, and for the different types of precipitation. Water stable isotopes are more closely related to 2 m air temperature than to inversion temperature at all timescales (e.g. R2 = 0.63 and 0.44, respectively for daily values). The slope of the temporal relationship between daily δ18O and 2 m air temperature is approximately 2 times smaller (0.49 ‰ °C−1) than the average Antarctic spatial (0.8 ‰ °C−1) relationship initially used for the interpretation of EPICA Dome C records. In accordance with results from precipitation monitoring at Vostok and Dome F, deuterium excess is anti-correlated with δ18O at daily and monthly scales, reaching maximum values in winter. Hoar frost precipitation samples have a specific fingerprint with more depleted δ18O (about 5 ‰ below average) and higher deuterium excess (about 8 ‰ above average) values than other precipitation types. These datasets provide a basis for comparison with shallow ice core records, to investigate post-deposition effects. A preliminary comparison between observations and precipitation from the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis and the simulated water stable isotopes from the Laboratoire de Météorologie Dynamique Zoom atmospheric general circulation model (LMDZiso) shows that models do correctly capture the amount of precipitation as well as more than 50 % of the variance of the observed δ18O, driven by large-scale weather patterns. Despite a warm bias and an underestimation of the variance in water stable isotopes, LMDZiso correctly captures these relationships between δ18O, 2 m air temperature and deuterium excess. Our dataset is therefore available for further in-depth model evaluation at the synoptic scale.

scholarly journals The isotopic composition of water vapour and precipitation in Ivittuut, southern Greenland

2014 ◽  
Vol 14 (9) ◽  
pp. 4419-4439 ◽  
Author(s):  
J.-L. Bonne ◽  
V. Masson-Delmotte ◽  
O. Cattani ◽  
M. Delmotte ◽  
C. Risi ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Isotopic Composition ◽  
Water Vapour ◽  
General Circulation ◽  
Winter Season ◽  
First Record ◽  
Back Trajectory ◽  
Deuterium Excess ◽  
Local Surface ◽  
Moisture Source

Abstract. Since September 2011, a wavelength-scanned cavity ring-down spectroscopy analyser has been remotely operated in Ivittuut, southern Greenland, providing the first record of surface water vapour isotopic composition based on continuous measurements in South Greenland and the first record including the winter season in Greenland. The comparison of vapour data with measurements of precipitation isotopic composition suggest an equilibrium between surface vapour and precipitation. δ18O and deuterium excess are generally anti-correlated and show important seasonal variations, with respective amplitudes of ~10 and ~20‰, as well as large synoptic variations. The data depict small summer diurnal variations. At the seasonal scale, δ18O has a minimum in November–December and a maximum in June–July, while deuterium excess has a minimum in May–June and a maximum in November. The approach of low-pressure systems towards South Greenland leads to δ18O increase (typically +5‰) and deuterium excess decrease (typically −15‰). Seasonal and synoptic variations coincide with shifts in the moisture sources, estimated using a quantitative moisture source diagnostic based on a Lagrangian back-trajectory model. The atmospheric general circulation model LMDZiso correctly captures the seasonal and synoptic variability of δ18O, but does not capture the observed magnitude of deuterium excess variability. Covariations of water vapour isotopic composition with local and moisture source meteorological parameters have been evaluated. δ18O is strongly correlated with the logarithm of local surface humidity, consistent with Rayleigh distillation processes, and with local surface air temperature, associated with a slope of ~0.4‰ °C−1. Deuterium excess correlates with local surface relative humidity as well as surface relative humidity from the dominant moisture source area located in the North Atlantic, south of Greenland and Iceland.

ON EVALUATION OF THE ROLE OF THERMAL AND WIND FACTORS FOR A PHYSICAL MODEL OF THE WORLD OCEAN GENERAL CIRCULATION SYSTEM

2019 ◽  
Vol 47 (3) ◽  
pp. 80-91
Author(s):  
V. G. Neiman
Keyword(s):  
Physical Model ◽  
Ocean Circulation ◽  
General Circulation ◽  
World Ocean ◽  
Circulation System ◽  
The Public ◽  
The World ◽  
Almost All ◽  
Conceptual Foundations

The main content of the work consists of certain systematization and addition of longexisting, but eventually deformed and partly lost qualitative ideas about the role of thermal and wind factors that determine the physical mechanism of the World Ocean’s General Circulation System (OGCS). It is noted that the conceptual foundations of the theory of the OGCS in one form or another are contained in the works of many well-known hydrophysicists of the last century, but the aggregate, logically coherent description of the key factors determining the physical model of the OGCS in the public literature is not so easy to find. An attempt is made to clarify and concretize some general ideas about the two key blocks that form the basis of an adequate physical model of the system of oceanic water masses motion in a climatic scale. Attention is drawn to the fact that when analyzing the OGCS it is necessary to take into account not only immediate but also indirect effects of thermal and wind factors on the ocean surface. In conclusion, it is noted that, in the end, by the uneven flow of heat to the surface of the ocean can be explained the nature of both external and almost all internal factors, in one way or another contributing to the excitation of the general, or climatic, ocean circulation.

Seasonal trends in the stable isotopic composition of snow and meltwater runoff in a subarctic catchment at Okstindan, Norway

2004 ◽  
Vol 35 (2) ◽  
pp. 119-137 ◽  
Author(s):  
S.D. Gurney ◽  
D.S.L. Lawrence
Keyword(s):  
Isotopic Composition ◽  
Mean Value ◽  
Mean Values ◽  
Stable Isotopic Composition ◽  
Meltwater Runoff ◽  
Stable Isotopic ◽  
The Mean ◽  
The Difference ◽  
Δ18o And Δd

Seasonal variations in the stable isotopic composition of snow and meltwater were investigated in a sub-arctic, mountainous, but non-glacial, catchment at Okstindan in northern Norway based on analyses of δ18O and δD. Samples were collected during four field periods (August 1998; April 1999; June 1999 and August 1999) at three sites lying on an altitudinal transect (740–970 m a.s.l.). Snowpack data display an increase in the mean values of δ18O (increasing from a mean value of −13.51 to −11.49‰ between April and August), as well as a decrease in variability through the melt period. Comparison with a regional meteoric water line indicates that the slope of the δ18O–δD line for the snowpacks decreases over the same period, dropping from 7.49 to approximately 6.2.This change points to the role of evaporation in snowpack ablation and is confirmed by the vertical profile of deuterium excess. Snowpack seepage data, although limited, also suggest reduced values of δD, as might be associated with local evaporation during meltwater generation. In general, meltwaters were depleted in δ18O relative to the source snowpack at the peak of the melt (June), but later in the year (August) the difference between the two was not statistically significant. The diurnal pattern of isotopic composition indicates that the most depleted meltwaters coincide with the peak in temperature and, hence, meltwater production.

scholarly journals Role of the Indo-Pacific Interbasin Coupling in Predicting Asymmetric ENSO Transition and Duration

2012 ◽  
Vol 25 (9) ◽  
pp. 3321-3335 ◽  
Author(s):  
Masamichi Ohba ◽  
Masahiro Watanabe
Keyword(s):  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Southern Oscillation ◽  
La Niña ◽  
La Nina ◽  
The Pacific ◽  
Enso Asymmetry ◽  
Sst Anomalies

Warm and cold phases of El Niño–Southern Oscillation (ENSO) exhibit a significant asymmetry in their transition/duration such that El Niño tends to shift rapidly to La Niña after the mature phase, whereas La Niña tends to persist for up to 2 yr. The possible role of sea surface temperature (SST) anomalies in the Indian Ocean (IO) in this ENSO asymmetry is investigated using a coupled general circulation model (CGCM). Decoupled-IO experiments are conducted to assess asymmetric IO feedbacks to the ongoing ENSO evolution in the Pacific. Identical-twin forecast experiments show that a coupling of the IO extends the skillful prediction of the ENSO warm phase by about one year, which was about 8 months in the absence of the IO coupling, in which a significant drop of the prediction skill around the boreal spring (known as the spring prediction barrier) is found. The effect of IO coupling on the predictability of the Pacific SST is significantly weaker in the decay phase of La Niña. Warm IO SST anomalies associated with El Niño enhance surface easterlies over the equatorial western Pacific and hence facilitate the El Niño decay. However, this mechanism cannot be applied to cold IO SST anomalies during La Niña. The result of these CGCM experiments estimates that approximately one-half of the ENSO asymmetry arises from the phase-dependent nature of the Indo-Pacific interbasin coupling.

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