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Lead Isotopic Constraints on the Provenance of Antarctic Dust and Atmospheric Circulation Patterns Prior to the Mid-Brunhes Event (~430 kyr ago)

2022-07-01T00:00:00Z

Title: Lead Isotopic Constraints on the Provenance of Antarctic Dust and Atmospheric Circulation Patterns Prior to the Mid-Brunhes Event (~430 kyr ago) Authors: Han, Changhee; Burn, Laurie J.; Vallelonga, Paul; Hur, Soon Do; Boutron, Claude F.; Han, Yeongcheol; Lee, Sanghee; Lee, Ahhyung; Hong, Sungmin Abstract: A lead (Pb) isotopic record, covering the two oldest glacial-interglacial cycles (~572 to 801 kyr ago) characterized by lukewarm interglacials in the European Project for Ice Coring in Antarctica Dome C ice core, provides evidence for dust provenance in central East Antarctic ice prior to the Mid-Brunhes Event (MBE), ~430 kyr ago. Combined with published post-MBE data, distinct isotopic compositions, coupled with isotope mixing model results, suggest Patagonia/Tierra del Fuego (TdF) as the most important sources of dust during both pre-MBE and post-MBE cold and intermediate glacial periods. During interglacials, central-western Argentina emerges as a major contributor, resulting from reduced dust supply from Patagonia/TdF after the MBE, contrasting to the persistent dominance of dust from Patagonia/TdF before the MBE. The data also show a small fraction of volcanic Pb transferred from extra-Antarctic volcanoes during post-MBE interglacials, as opposed to abundant transfer prior to the MBE. These differences are most likely attributed to the enhanced wet removal efficiency with the hydrological cycle intensified over the Southern Ocean, associated with a poleward shift of the southern westerly winds (SWW) during warmer post-MBE interglacials, and vice versa during cooler pre-MBE ones. Our results highlight sensitive responses of the SWW and the associated atmospheric conditions to stepwise Antarctic warming.

Chronological characteristics for snow accumulation on Styx Glacier in northern Victoria Land, Antarctica

2020-12-01T00:00:00Z

Title: Chronological characteristics for snow accumulation on Styx Glacier in northern Victoria Land, Antarctica Authors: Nyamgerel, Yalalt; Han, Yeongcheol; Kim, Songyi; Hong, Sang-Bum; Lee, Jeonghoon; Hur, Soon Do Abstract: Under the potential to reconstruct the past climatic and atmospheric conditions from a deep ice core in the coastal Antarctic site (Styx Glacier), an 8.84m long firn core (73°50.975′ S, 163° 41.640′ E; 1623m a.s.l.) was initially studied to propose a reliable age scale for the local estimation of snow accumulation rate. The seasonal variations of δ18O, methanesulfonic acid (MSA) and non-sea-salt sulfate (nssSO4 2？) were used for the firn core dating and revealed 25 annual peaks (from 1990 to 2014) with volcanic sulfate signal. The observed declining trend in annual accumulation rate with a mean value of 146 ± 60 kgm？2 a？1 is likely to be linked to the changes of seaice extent in the Ross Sea region. Moreover, the temporal variation of the annual mean δ18O, an annual flux of MSA and nssSO42？ also likely to be under the influence of ice-covered and open water area. This study suggests a potential to recover past changes in an oceanic environment and will be useful for the interpretation of the long ice core drilled at the same site.

An improved ion chromatography system coupled with a melter for high resolution ionic species reconstruction in Antarctic firn cores

2020-12-01T00:00:00Z

Title: An improved ion chromatography system coupled with a melter for high resolution ionic species reconstruction in Antarctic firn cores Authors: Seokhyun, Ro; Hur, Soon Do; Hong, Sungmin; Chang, Chaewon; Moon, Jangil; Han, Yeongcheol; Jun, Seong Joon; Hwang, Heejin; Hong, Sang-Bum Abstract: We improved an on-line multi-ion chromatography (IC) system combined with a custom firn core melter (IC-melter). Five anions (F-, CH3SO3-, Cl-, NO3-, SO42-) and five cations (Na+, NH4+, K+, Mg2+, Ca2+) are simultaneously determined every 1.3 min; high-resolution ion data, with a depth interval of approximately 1.8 cm, can thus be obtained from Antarctic firn cores using the IC-melter. The IC-melter provides a processing speed of 1.1-1.7 h per similar to 0.7-0.8 m firn core. The depth resolution was designed to capture seasonal variations of ions based on the accumulation rate of Styx Glacier (Northern Victoria Land, Antarctica), where a firn core used herein was obtained, and variations of the firn core density. The analytical conditions (eluent concentration and flow rate, run time, peak separation, and sensitivity) of the multi-IC system were optimized to achieve the research goals. Cations and anions were separated through 4-min isocratic elution (CH3SO3H eluent) and 5-min isocratic elution (KOH eluent), respectively. The isocratic elution method for anion analysis was selected, rather than the gradient elution method, due to the exceptionally low ionic strength of the meltwater and easy operation of the multi-IC system. All ionic species showed calibration curves with determinant coefficients > 0.997, standard errors of estimated values < 0.015, and relative standard deviation values < 4.2% for anions and < 2.4% for cations at levels of 5-25 μg L-1. The method detection limits (MDLs) for assessed ions were comparable to detection limits (DLs) previously reported for on-line IC-melter systems, except the limit of SO42- (~3.0 μg L-1). In particular, the MDLs of fluoride ion (F-) and methanesulfonate ion (CH3SO3-) were 0.03 and 0.3 μg L-1, respectively; these species were successfully measured in an Antarctic firn core for the first time, using the improved on-line IC-melter. The relative errors for ions other than Na+ and Cl- were generally < 11.1% at a level of approximately 50 μg L-1. The expanded measurement uncertainties (k = 2 at the 95% confidence level) were ~0.13 μg L-1 and ~1.59 μg L-1 at levels of ~1.0 μg L-1 for F- and ~5.0 μg L-1 for CH3SO3-, respectively. The measured ions from parallel two firn core stick samples showed reproducibility values < 30%. Pearson’s r values between ions obtained from the IC-melter and conventional method were > 0.67. In this study, as an application of the IC-melter, high-resolution ion species data from the firn core (depth interval: ~20.11-22.85 m) are shortly presented.

Reliable Ultra Trace Analysis of Cd, U and Zn Concentrations in Greenland Snow and Ice by Using Ultraclean Methods for Contamination Control

2020-06-01T00:00:00Z

Title: Reliable Ultra Trace Analysis of Cd, U and Zn Concentrations in Greenland Snow and Ice by Using Ultraclean Methods for Contamination Control Authors: Han, Changhee; Hwang, Heejin; Kang, Jung-Ho; Hong, Sang-Bum; Han, Yeongcheol; Lee, Khanghyun; Hur, Soon Do; Hong, Sungmin Abstract: This study presents ultraclean procedures used in the challenging task of determining trace elements at or below the pg/g concentration level encountered in Greenland snow and ice. In order to validate these ultraclean procedures, recent snowfall and Holocene ice from northwest Greenland were analyzed for Cd, U, and Zn concentrations. The total procedural blanks brought through the entire measurement procedure proved to be negligible, compared to trace element concentrations, measured in snow and ice samples. This validates the overall practicality of the proposed ultraclean procedures, thereby ensuring the reliable measurements of ultra-trace analysis. A comparison between our study and published data shows that improper procedures employed throughout all stages, from field sampling to analysis to elevate the concentrations by several orders of magnitude, relative to the reliable concentration ranges. The risk of contamination exposure for selected trace elements appears to increase in the order of U < As Pb < Cd < Zn. Reliable measurements of Cd, U, and Zn concentrations in snow and ice allowed us to interpret the data in terms of seasonal variations in the inputs of crustal and anthropogenic sources to Greenland ice sheet.