Challenges associated with the climatic interpretation of water stable isotope records from a highly resolved firn core from Adélie Land, coastal Antarctica

Abstract. A new 21.3 m firn core was drilled in 2015 at a coastal Antarctic high-accumulation site in Adélie Land (66.78∘ S; 139.56∘ E, 602 m a.s.l.), named Terre Adélie 192A (TA192A). The mean isotopic values (-19.3‰±3.1 ‰ for δ18O and 5.4 ‰±2.2 ‰ for deuterium excess) are consistent with other coastal Antarctic values. No significant isotope–temperature relationship can be evidenced at any timescale. This rules out a simple interpretation in terms of local temperature. An observed asymmetry in the δ18O seasonal cycle may be explained by the precipitation of air masses coming from the eastern and western sectors in autumn and winter, recorded in the d-excess signal showing outstanding values in austral spring versus autumn. Significant positive trends are observed in the annual d-excess record and local sea ice extent (135–145∘ E) over the period 1998–2014. However, process studies focusing on resulting isotopic compositions and particularly the deuterium excess–δ18O relationship, evidenced as a potential fingerprint of moisture origins, as well as the collection of more isotopic measurements in Adélie Land are needed for an accurate interpretation of our signals.

Download Full-text

Challenges associated with the climatic interpretation of water stable isotope records from a highly resolved firn core from Adélie Land, coastal Antarctica

10.5194/tc-2018-121 ◽

2018 ◽

Author(s):

Sentia Goursaud ◽

Valérie Masson-Delmotte ◽

Vincent Favier ◽

Suzanne Preunkert ◽

Michel Legrand ◽

...

Keyword(s):

Stable Isotope ◽

Sea Ice ◽

General Circulation ◽

Circulation Model ◽

Austral Spring ◽

High Accumulation ◽

Sea Ice Concentration ◽

Water Stable Isotope ◽

The Mean ◽

Firn Core

Abstract. A new 21.3 m firn core was drilled in 2015 at a coastal Antarctic high accumulation site in Adélie Land (66.78 °S; 139.56 °E, 602 m a.s.l.). The core was dated by annual layers counting based on non-sea-salt sulfate and methanesulfonate summer peaks, refined by a comparison between the reconstructed surface mass balance (hereafter, SMB) and the closest available stake data. The mean reconstructed SMB of 75.2 ± 15.0 cm w.e. y−1 is consistent with local stake data, and remarkably high for coastal East Antarctica. The resulting inter-annual and sub-annual variations in isotopic records (δ18O and deuterium excess, hereafter d-excess) are explored for 1998–2014 and are systematically compared with a couple of climatic time series: an updated database of Antarctic surface snow isotopic composition, SMB stake data, meteorological observations from Dumont d'Urville station, sea-ice concentration based on passive microwave satellite data, precipitation outputs of atmospheric reanalyses, climate and water stable isotope outputs from the atmospheric general circulation model ECHAM5-wiso, as well as air mass origins diagnosed using 5-days back-trajectories. The mean isotopic values (−19.3 ± 3.1 ‰ for δ18O and 5.4 ± 2.2 ‰ for d-excess) are consistent with other coastal Antarctic values. No significant isotope-temperature relationship can be evidenced at any timescale, ruling out a simple interpretation of in terms of local temperature. An observed asymmetry in the δ18O seasonal cycle may be explained by the precipitation of air masses coming from Indian and Pacific/West Antarctic Ice Sheet sectors in autumn and winter times, recorded in the d-excess signal showing outstanding values in austral spring versus autumn. Significant positive trends are observed in the annual d-excess record and local sea-ice extent (135 °E–145 °E) over the period 1998–2014. However, processes studies focusing on resulting isotopic compositions and particularly the d-excess-δ18O relationship, evidenced as a potential fingerprint of moisture origins, as well as the collection of more isotopic measurements in Adélie Land are needed for an accurate interpretation of our signals.

Download Full-text

Stable-isotope time series and precipitation origin from firn-core and snow samples, Altai glaciers, Siberia

Journal of Glaciology ◽

10.3189/172756505781829034 ◽

2005 ◽

Vol 51 (175) ◽

pp. 637-654 ◽

Cited By ~ 33

Author(s):

Vladimir B. Aizen ◽

Elena Aizen ◽

Koji Fujita ◽

Stanislav A. Nikitin ◽

Karl J. Kreutz ◽

...

Keyword(s):

Stable Isotope ◽

Clustering Analysis ◽

Meteoric Water ◽

Drainage Basin ◽

The Arctic ◽

Deuterium Excess ◽

Closed Drainage ◽

Water Stable Isotope ◽

Firn Core ◽

Snow Samples

AbstractIn the summers of 2001 and 2002, glacio-climatological research was performed at 4110–4120 m a.s.l. on the Belukha snow/firn plateau, Siberian Altai. Hundreds of samples from snow pits and a 21 m snow/firn core were collected to establish the annual/seasonal/monthly depth–accumulation scale, based on stable-isotope records, stratigraphic analyses and meteorological and synoptic data. The fluctuations of water stable-isotope records show well-preserved seasonal variations. The δ18O and δD relationships in precipitation, snow pits and the snow/firn core have the same slope to the covariance as that of the global meteoric water line. The origins of precipitation nourishing the Belukha plateau were determined based on clustering analysis of δ18O and d-excess records and examination of synoptic atmospheric patterns. Calibration and validation of the developed clusters occurred at event and monthly timescales with about 15% uncertainty. Two distinct moisture sources were shown: oceanic sources with d-excess <12‰, and the Aral–Caspian closed drainage basin sources with d-excess >12‰. Two-thirds of the annual accumulation was from oceanic precipitation, of which more than half had isotopic ratios corresponding to moisture evaporated over the Atlantic Ocean. Precipitation from the Arctic/Pacific Ocean had the lowest deuterium excess, contributing one-tenth to annual accumulation.

Download Full-text

Sea ice-related halogen enrichment at Law Dome, coastal East Antarctica

10.5194/cp-2016-74 ◽

2016 ◽

Cited By ~ 1

Author(s):

Paul Vallelonga ◽

Niccolo Maffezzoli ◽

Andrew D. Moy ◽

Mark A. J. Curran ◽

Tessa R. Vance ◽

...

Keyword(s):

Sea Ice ◽

20Th Century ◽

East Antarctica ◽

Austral Spring ◽

High Accumulation ◽

Low Levels ◽

The Law ◽

Western Side ◽

The Antarctic ◽

Firn Core

Abstract. The Law Dome site is ideal for the evaluation of sea ice proxies due to its location near to the Antarctic coast, regular and high accumulation throughout the year, an absence of surface melting or remobilization, and minimal multiyear sea ice. We present records of bromine and iodine concentrations and their enrichment beyond seawater compositions, arguing that halogen enrichment is indicative of the local sea ice area, particularly the 90–110° E sector of the Wilkes coast. Our findings support the results of previous studies of sea ice variability from Law Dome, indicating that Wilkes coast sea ice area is currently at its lowest level since the start of the 20th century. From the Law Dome DSS1213 firn core, 26 years of monthly deposition data indicate that the period of peak bromine enrichment is during Austral spring-summer, from November to February. Results from a traverse along the lee (Western) side of Law Dome show low levels of sodium and bromine deposition, with the greatest fluxes in the vicinity of the Law Dome summit. Finally, iodine enrichment is well correlated to that of bromine, indicating a common, sea ice source for their enrichment.

Download Full-text

First glaciological investigations at Ridge B, central East Antarctica

Antarctic Science ◽

10.1017/s0954102021000171 ◽

2021 ◽

pp. 1-10

Author(s):

Alexey A. Ekaykin ◽

Alexey V. Bolshunov ◽

Vladimir Ya. Lipenkov ◽

Mirko Scheinert ◽

Lutz Eberlein ◽

...

Keyword(s):

East Antarctica ◽

Snow Density ◽

Deep Drilling ◽

Surface Mass ◽

Annual Variations ◽

First Results ◽

Vostok Station ◽

Water Stable Isotope ◽

Isotope Content ◽

Firn Core

Abstract The region of Ridge B in central East Antarctica is one of the last unexplored parts of the continent and, at the same time, ranks among the most promising places to search for Earth's oldest ice. In January 2020, we carried out the first scientific traverse from Russia's Vostok Station to the topographical dome of Ridge B (Dome B, 3807 m above sea level, 79.02°S, 93.69°E). The glaciological programme included continuous snow-radar profiling and geodetic positioning along the traverse's route, installation of snow stakes, measurements of snow density, collection of samples for stable water isotope and chemical analyses and drilling of a 20 m firn core. The first results of the traverse show that the surface mass balance at Dome B (2.28 g cm−2 year−1) is among the lowest in Antarctica. The firn temperature below the layer of annual variations is −58.1 ± 0.2°C. A very low value of heavy water stable isotope content (-58.2‰ for oxygen-18) was discovered at a distance of 170 km from Vostok Station. This work is the first step towards a comprehensive reconnaissance study of the Ridge B area aimed at locating the best site for future deep drilling for the oldest Antarctic ice.

Download Full-text

Conditions leading to the unprecedented low Antarctic sea ice extent during the 2016 austral spring season

Geophysical Research Letters ◽

10.1002/2017gl074691 ◽

2017 ◽

Vol 44 (17) ◽

pp. 9008-9019 ◽

Cited By ~ 57

Author(s):

Malte F. Stuecker ◽

Cecilia M. Bitz ◽

Kyle C. Armour

Keyword(s):

Sea Ice ◽

Spring Season ◽

Austral Spring ◽

Sea Ice Extent ◽

Antarctic Sea Ice

Download Full-text

Spatial gradients of temperature, accumulation and δ<sup>18</sup>O-ice in Greenland over a series of Dansgaard–Oeschger events

Climate of the Past ◽

10.5194/cp-9-1029-2013 ◽

2013 ◽

Vol 9 (3) ◽

pp. 1029-1051 ◽

Cited By ~ 48

Author(s):

M. Guillevic ◽

L. Bazin ◽

A. Landais ◽

P. Kindler ◽

A. Orsi ◽

...

Keyword(s):

Flow Model ◽

Ice Cores ◽

Ice Age ◽

Age Difference ◽

Sea Ice Extent ◽

Ice Flow ◽

Spatial Gradients ◽

Climate Simulations ◽

Precipitation Seasonality ◽

Water Stable Isotope

Abstract. Air and water stable isotope measurements from four Greenland deep ice cores (GRIP, GISP2, NGRIP and NEEM) are investigated over a series of Dansgaard–Oeschger events (DO 8, 9 and 10), which are representative of glacial millennial scale variability. Combined with firn modeling, air isotope data allow us to quantify abrupt temperature increases for each drill site (1σ = 0.6 °C for NEEM, GRIP and GISP2, 1.5 °C for NGRIP). Our data show that the magnitude of stadial–interstadial temperature increase is up to 2 °C larger in central and North Greenland than in northwest Greenland: i.e., for DO 8, a magnitude of +8.8 °C is inferred, which is significantly smaller than the +11.1 °C inferred at GISP2. The same spatial pattern is seen for accumulation increases. This pattern is coherent with climate simulations in response to reduced sea-ice extent in the Nordic seas. The temporal water isotope (δ18O)–temperature relationship varies between 0.3 and 0.6 (±0.08) ‰ °C−1 and is systematically larger at NEEM, possibly due to limited changes in precipitation seasonality compared to GISP2, GRIP or NGRIP. The gas age−ice age difference of warming events represented in water and air isotopes can only be modeled when assuming a 26% (NGRIP) to 40% (GRIP) lower accumulation than that derived from a Dansgaard–Johnsen ice flow model.

Download Full-text

Aerosol characterization at the Saharan AERONET site Tamanrasset

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-11753-2014 ◽

2014 ◽

Vol 14 (21) ◽

pp. 11753-11773 ◽

Cited By ~ 31

Author(s):

C. Guirado ◽

E. Cuevas ◽

V. E. Cachorro ◽

C. Toledano ◽

S. Alonso-Pérez ◽

...

Keyword(s):

Precipitable Water ◽

Saharan Dust ◽

Dust Particles ◽

Data Series ◽

Precipitable Water Vapour ◽

Convective Boundary ◽

Air Masses ◽

Fine Mode ◽

Autumn And Winter ◽

Sky Conditions

Abstract. More than 2 years of columnar atmospheric aerosol measurements (2006–2009) at the Tamanrasset site (22.79° N, 5.53° E, 1377 m a.s.l.), in the heart of the Sahara, are analysed. Aerosol Robotic Network (AERONET) level 2.0 data were used. The KCICLO (K is the name of a constant and ciclo means cycle in Spanish) method was applied to a part of the level 1.5 data series to improve the quality of the results. The annual variability of aerosol optical depth (AOD) and Ångström exponent (AE) has been found to be strongly linked to the convective boundary layer (CBL) thermodynamic features. The dry-cool season (autumn and winter) is characterized by a shallow CBL and very low mean turbidity (AOD ~ 0.09 at 440 nm, AE ~ 0.62). The wet-hot season (spring and summer) is dominated by high turbidity of coarse dust particles (AE ~ 0.28, AOD ~ 0.39 at 440 nm) and a deep CBL. The aerosol-type characterization shows desert mineral dust as the prevailing aerosol. Both pure Saharan dust and very clear sky conditions are observed depending on the season. However, several case studies indicate an anthropogenic fine mode contribution from the industrial areas in Libya and Algeria. The concentration weighted trajectory (CWT) source apportionment method was used to identify potential sources of air masses arriving at Tamanrasset at several heights for each season. Microphysical and optical properties and precipitable water vapour were also investigated.

Download Full-text

Extreme Anomalous Atmospheric Circulation in the West Antarctic Peninsula Region in Austral Spring and Summer 2001/02, and Its Profound Impact on Sea Ice and Biota*

Journal of Climate ◽

10.1175/jcli3805.1 ◽

2006 ◽

Vol 19 (15) ◽

pp. 3544-3571 ◽

Cited By ~ 88

Author(s):

Robert A. Massom ◽

Sharon E. Stammerjohn ◽

Raymond C. Smith ◽

Michael J. Pook ◽

Richard A. Iannuzzi ◽

...

Keyword(s):

Sea Ice ◽

Antarctic Peninsula ◽

Phytoplankton Bloom ◽

Wide Field ◽

The West ◽

Austral Spring ◽

Sea Ice Extent ◽

Ice Dynamics ◽

West Antarctic ◽

West Antarctic Peninsula

Abstract Exceptional sea ice conditions occurred in the West Antarctic Peninsula (WAP) region from September 2001 to February 2002, resulting from a strongly positive atmospheric pressure anomaly in the South Atlantic coupled with strong negative anomalies in the Bellingshausen–Amundsen and southwest Weddell Seas. This created a strong and persistent north-northwesterly flow of mild and moist air across the WAP. In situ, satellite, and NCEP–NCAR Reanalysis (NNR) data are used to examine the profound and complex impact on regional sea ice, oceanography, and biota. Extensive sea ice melt, leading to an ocean mixed layer freshening and widespread ice surface flooding, snow–ice formation, and phytoplankton growth, coincided with extreme ice deformation and dynamic thickening. Sea ice dynamics were crucial to the development of an unusually early and rapid (short) retreat season (negative ice extent anomaly). Strong winds with a dominant northerly component created an unusually compact marginal ice zone and a major increase in ice thickness by deformation and over-rafting. This led to the atypical persistence of highly compact coastal ice through summer. Ecological effects were both positive and negative, the latter including an impact on the growth rate of larval Antarctic krill and the largest recorded between-season breeding population decrease and lowest reproductive success in a 30-yr Adélie penguin demographic time series. The unusual sea ice and snow cover conditions also contributed to the formation of a major phytoplankton bloom. Unexpectedly, the initial bloom occurred within compact sea ice and could not be detected in Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) ocean color data. This analysis demonstrates that sea ice extent alone is an inadequate descriptor of the regional sea ice state/conditions, from both a climatic and ecological perspective; further information is required on thickness and dynamics/deformation.

Download Full-text

Sea-ice-related halogen enrichment at Law Dome, coastal East Antarctica

Climate of the Past ◽

10.5194/cp-13-171-2017 ◽

2017 ◽

Vol 13 (2) ◽

pp. 171-184 ◽

Cited By ~ 6

Author(s):

Paul Vallelonga ◽

Niccolo Maffezzoli ◽

Andrew D. Moy ◽

Mark A. J. Curran ◽

Tessa R. Vance ◽

...

Keyword(s):

Sea Ice ◽

First Year ◽

Common Source ◽

Interdecadal Pacific Oscillation ◽

Austral Spring ◽

High Accumulation ◽

Low Levels ◽

The Law ◽

Western Side ◽

The Antarctic

Abstract. The Law Dome site is ideal for the evaluation of sea ice proxies due to its location near to the Antarctic coast, regular and high accumulation throughout the year, an absence of surface melting or remobilization, and minimal multiyear sea ice. We present records of bromine and iodine concentrations and their enrichment beyond seawater compositions and compare these to satellite observations of first-year sea ice area in the 90–130° E sector of the Wilkes coast. Our findings support the results of previous studies of sea ice variability from Law Dome, indicating that Wilkes coast sea ice area is currently at its lowest level since the start of the 20th century. From the Law Dome DSS1213 firn core, 26 years of monthly deposition data indicate that the period of peak bromine enrichment is during austral spring–summer, from November to February. Results from a traverse along the lee (western) side of Law Dome show low levels of sodium and bromine deposition, with the greatest fluxes in the vicinity of the Law Dome summit. Finally, multidecadal variability in iodine enrichment appears well correlated to bromine enrichment, suggesting a common source of variability that may be related to the Interdecadal Pacific Oscillation (IPO).

Download Full-text

Atmospheric bromoform at Cape Point, South Africa: a first time series on the African continent

10.5194/acp-2017-244 ◽

2017 ◽

Author(s):

Brett Kuyper ◽

Carl J. Palmer ◽

Casper Labuschagne ◽

Chris J. C. Reason

Keyword(s):

South Africa ◽

Austral Spring ◽

Data Set ◽

Air Masses ◽

Mixing Ratios ◽

Front End ◽

Potential Source ◽

High Concentrations ◽

Marine Air ◽

First Time

Abstract. Bromoform mixing ratios in marine air were measured at Cape Point Global Atmospheric Watch Station, South Africa. This represents the first ever bromoform data set recorded at this unique location. Manual daily measurements were made during a month long field campaign (austral spring 2011) using a GC-ECD with a custom built front end thermal desorption trap. The measured concentrations ranged between 2.3 ± 0.4 and 84.7 ± 10.8 ppt with a mean of 24.7 ± 3.1 ppt. Our analysis shows the concentration of bromform varies significantly according to wind direction and the trajectory of the air mass sampled. Air masses which had come into contact with multiple potential source of bromoform showed the highest average mixing ratios. The measurements reported here represent some of the highest recorded coastal bromoform concentrations globally. These high concentrations may be explained by the multiple local sources of bromoform around Cape Point.

Download Full-text