Glaciochemical Record Research Articles

Two decades ammonium records from ice core in Qiangyong glacier in the Northern Himalayas

The increase in anthropogenic emissions and associated climate change have become a growing critical environmental concern, with significant implications for human health and ecological security. The rapid economic growth in South Asia has contributed additional stress on the atmospheric environment in the surrounding regions. Earlier ice core chemical studies revealed a strong atmospheric transport to the Himalayan region from South Asia through the Indian summer monsoon. Continuous observation of atmosphere chemistry is not yet available, while ice core chemical record from high mountain regions can serve as an alternative proxy. So far, the influence of these transports on the southern Tibetan Plateau has not been adequately evaluated as only a few glaciochemical records are rebuilt. Here, we present a chemical record from a shallow ice core (with depth of 21.4 m), which was retrieved from the Qiangyong Glacier in the rain-shadow area of the Himalayas drilled in 2009and dated back to the past 23 years of 1987–2009. The primary objective was to retrieve glaciochemical record and establish possible sources of soluble components, in particular those of NH4+. Empirical orthogonal function (EOF) analysis on the eight major ions series (Ca2+, Na+, Mg2+, NH4+, K+, Cl−, NO3−, SO42−) from this core reveals that NH4+ is loaded primarily separately on EOF3, likely suggesting a specific source out of the other ion signals. Both a back-trajectory model and the correlation analysis between NH4+ and SO42− indicate the anthropogenic origin from South Asia. Although earlier ice core records showed a curbed increasing trend in NH4+, our new data reveals that the increasing trend continued after 1980 and experienced a rapid increase after 2000. This trend is in accordance with the increasing population and agriculture activities in South Asia, corresponding with increasing anthropogenic emission. Spatial comparison of the Qiangyong ice core record with existing NH4+ records from other ice cores in the Tibetan Plateau show that concentrations of NH4+ are regionally increasing. However, the relatively small rise in Qiangyong record is probably in association with the effective transportation barrier of the Himalayas. This study advances the knowledge of atmospheric environmental change in the northern Himalayas and the air mass transport of anthropogenic pollutants from South Asia to the southern Tibetan Plateau via the summer Indian monsoon.

Glaciochemical records for the past century from the Qiangtang Glacier No.1 ice core on the central Tibetan Plateau: Likely proxies for climate and atmospheric circulations

Previous studies of glaciochemical records retrieved from the southern and northern sectors of the Tibetan Plateau (TP) have revealed that there are diverse patterns of climate change within this region. However, uncertainty remains regarding changes in the atmospheric environment over the central TP where the Indian monsoonal circulation and westerly winds meet. This study presents a glaciochemical record of the past 112 years from the upper part of the ice core drilled into the Qiangtang Glacier No.1 (QT-1) located in the central TP. The purpose of this study is to understand the glaciochemical controls, if any, and how these controls have been affected by both local climate parameters and atmospheric circulation patterns. An empirical orthogonal function (EOF) analysis was performed to determine the significance of any chemical components. The results show that the major soluble ions (Na+, K+, Mg2+, Ca2+, Cl−, NO3−, NH4+ and SO42−) are predominantly controlled by crustal aerosols and have high loadings on EOF1. Correlation analysis between EOF1 and the annual dust-event frequency recorded by local/regional meteorological stations suggests that the ice core chemical record provides a reasonable proxy for local/regional atmospheric dust loading. Analysis of EOF1 also demonstrates changes that are consistent with regional meteorological parameters and large-scale circulations, revealing a strong link with the glaciochemical record. The windy, cold-dry climate and/or enhanced northwesterly/westerly winds appear to be responsible for the higher atmospheric dust aerosols, leading to higher concentrations of ions. Our analysis also isolated a significant positive correlation between EOF1 and the Pacific Decadal Oscillation (PDO) index, suggesting that, as an underlying mechanism, the PDO likely influences the regional climate conditions and atmospheric circulation patterns and thereby the QT-1 ion records. Our findings may, therefore, enhance the understanding of the relationship between chemical records and climatological variations that are preserved in ice cores, improve our knowledge of changes in the composition of the atmosphere and atmospheric circulation over the central TP, and potentially facilitate reconstruction of the paleo-PDO.

Trace-element and physical response to melt percolation in Summit (Greenland) snow

AbstractSurface melt on a glacier can perturb the glaciochemical record beyond the natural variability. While the centre of the Greenland ice sheet is usually devoid of surface melt, many high-Arctic and alpine ice cores document frequent summertime melt events. Current hypotheses interpreting melt-affected ice-core chemistry rely on preferential elution of certain major ions. However, the precise nature of chemistry alteration is unknown because it is difficult to distinguish natural variability from melt effects in a perennially melt-affected site. We use eight trace-element snow chemistry records recovered from Summit, Greenland, to study spatial variability and melt effects on insoluble trace chemistry and physical stratigraphy due to artificially introduced meltwater. Differences between non-melt and melt-affected chemistry were significantly greater than the spatial variability in chemistry represented by nearest-neighbour pairs. Melt-perturbed trace elements, particularly rare earth elements, retained their seasonal stratigraphies, suggesting that trace elements may serve as robust chemical indicators for annual layers even in melt-affected study areas. Results suggest trace-element transport via meltwater percolation will deposit eluted material down-pit in refrozen areas below the nearest-surface chemistry peak. In our experiments, snow chemistry analyses are more sensitive to melt perturbations than density changes or unprocessed near-infrared digital imagery.

Little Ice Age climate and oceanic conditions of the Ross Sea, Antarctica from a coastal ice core record

Abstract. Increasing paleoclimatic evidence suggests that the Little Ice Age (LIA) was a global climate change event. Understanding the forcings and associated climate system feedbacks of the LIA is made difficult by the scarcity of Southern Hemisphere paleoclimate records. We use a new glaciochemical record of a coastal ice core from Mt. Erebus Saddle, Antarctica, to reconstruct atmospheric and oceanic conditions in the Ross Sea sector of Antarctica over the past five centuries. The LIA is identified in stable isotope (δD) and lithophile element records, which respectively demonstrate that the region experienced 1.6 ± 1.4 °C cooler average temperatures prior to 1850 AD than during the last 150 yr and strong (>57 m s−1) prevailing katabatic winds between 1500 and 1800 AD. Al and Ti concentration increases of an order of magnitude (>120 ppb Al) are linked to enhanced aeolian transport of complex silicate minerals and represent the strongest katabatic wind events of the LIA. These events are associated with three 12–30 yr intervals of cooler temperatures at ca. 1690 AD, 1770 AD and 1840 AD. Furthermore, ice core concentrations of the biogenic sulphur species MS− suggest that biological productivity in the Ross Sea polynya was ~80% higher prior to 1875 AD than at any subsequent time. We propose that cooler Antarctic temperatures promoted stronger katabatic winds across the Ross Ice Shelf, resulting in an enlarged Ross Sea polynya during the LIA.

Anthropogenic sulfate and nitrate signals in snow from Bogda Glacier, eastern Tianshan

A 1.2 m snow pit was recovered on July 29th, 2009 from the Bogda Glacier, eastern Tianshan (天山). The sample site temperature of −9.6 °C indicates that the unique glaciochemical record was well preserved and suitable for the reconstruction of air pollution levels in this previously unexplored region. Samples were analyzed for major ions (Na+, K+, Ca2+, Mg2+, NH4+, Cl−, SO42−, NO3−, HCOO−, and CH3COO−). NO3− and SO42− were characterized by significant high levels of pollution concentration. Most air masses backward trajectories ending in December 2008 have passed the Urumqi City center, while some even traveled across the primary nuclear weapons testing venue of the former Soviet Union (STS). The mean pH value of snow samples is coincident with the average value of Urumqi’s aerosol, and the ratio of [NO3−]/[SO42−] in the snow pit generally agrees with the value of the Urumqi winter aerosols. In addition, the [HCOO−]/[CH3COO−] ratio of snow samples is only 0.7, lower than unity. These analyses indicate that SO42− and NO3− in the Bogda Glacier are the result of anthropogenic pollutions.

The last interglacial as represented in the glaciochemical record from Mount Moulton Blue Ice Area, West Antarctica

Understanding climate during the last interglacial is critical for understanding how modern climate change differs from purely naturally forced climate change. Here we present the first high-resolution ice core record of the last interglacial and transition to the subsequent glacial period from Antarctica and the first glaciochemical record for this period from West Antarctica. Samples were collected from a horizontal ice trench in the Mt. Moulton Blue Ice Area (BIA) in West Antarctica and analyzed for their soluble major anions (Cl −, NO 3 −, SO 4 2-), major and trace elements (Na, Mg, Ca, Sr, Cd, Cs, Ba, La, Ce, Pr, Pb, Bi, U, As, Al, S, Ti, V, Cr, Mn, Fe, Co, Cu, Zn) and water hydrogen isotopes (δD). The last interglacial is characterized by warmer temperatures (δD), weakened atmospheric circulation (dust elements, seasalts aerosols), decreased sea ice extent (Na, nssSO 4 2-) and decreased oceanic productivity (nssSO 4 2-). A combined examination of Mt. Moulton seasalts, dust, nssSO 4 2- and δD records indicates that the last interglacial was extremely stable compared to glacial age climate events and it ended through a long period of gradual cooling unlike that projected for future Holocene climate.

Glaciochemical evidence in an East Antarctica ice core of a recent (AD 1450–1850) neoglacial episode

Chemical analysis of a shallow (82.5 m) ice core from a location (DT263) in the essentially unexplored area of Princess Elizabeth Land, East Antarctica, has been used to construct a continuous, high‐resolution 780‐year (AD 1207–1996) glaciochemical record. During the twentieth century, snow accumulation rates and concentrations of chemical species in snow appear to be stable with short‐term variations, indicating relatively stable and warm climatic conditions. The period of AD 1450–1850 in this record is characterized by sharply reduced snow accumulation rates and decreased concentrations of several chemical species that suffer postdepositional losses linked to very low accumulation rates. These characteristics are consistent with colder climatic conditions and suggest that this is likely a neoglacial episode. The timing of this episode coincides with the Little Ice Age (LIA), a relatively cold period in the Northern Hemisphere between the beginning of the fifteenth century and the end of the nineteenth century. Evidence in ice core and sedimentary records also indicates neoglacial conditions in some Southern Hemisphere locations during the general time frame of LIA. The DT263 record, along with a few published ice core records, points to the existence of an LIA‐type climatic episode in Antarctica between the fifteenth century and the twentieth century. However, other Antarctic ice core records show no such evidence. Together, these records highlight the regional differences in Holocene climate variations in Antarctica. The DT263 record suggests that colder and drier conditions prevailed during the LIA time period at the eastern Indian Ocean sector of East Antarctica.

Recent high-resolution glaciochemical record from a Dasuopu firn core of middle Himalayas

A 16.8 m firn core of middle Himalayas was recovered on the col of Dasuopu glacier in August 2006, being 7000 m above sea level. A total of 317 samples were measured for stable oxygen isotope ratios (δ18O) and major ion concentrations (Na+, NH4+, K+, Mg2+, Ca2+, Cl−, SO42−, and NO3−). The firn core dating and seasonal partitioning were carried out based on the marked seasonal variations along the stable oxygen isotopes and crustal species (Ca2+, Mg2+) profiles. The multi-parameters and high-resolution glaciochemical data set of Dasuopu firn core recorded the detailed chemical characteristics of precipitation in high-elevation region, middle Himalayas, since 1991 A.D., which mainly originated from the crustal and anthropogenic sources, while the sea-salt contribution was minor. The seasonal variability of major ion concentrations was dominated by the seasonal alternation of the prevalent air mass, atmospheric circulation situation and precipitation regime. Linear regression analysis indicated that most of the variance in annual ionic fluxes can be explained by a linear dependence on snow accumulation rate.

Sea level pressure variability over the southern Indian Ocean inferred from a glaciochemical record in Princess Elizabeth Land, east Antarctica

A 250‐year, high‐resolution, multivariate ice core record from LGB65 (70°50′07″S, 77°04′29″E; 1850 m asl), Princess Elizabeth Land (PEL), is used to investigate sea level pressure (SLP) variability over the southern Indian Ocean (SIO). Empirical orthogonal function (EOF) analysis reveals that the first EOF (EOF1) of the glaciochemical record from LGB65 represents most of the variability in sea salt throughout the 250‐year record. EOF1 is negatively correlated (95% confidence level and higher) to instrumental mean sea level pressure (MSLP) at Kerguelen and New Amsterdam islands, SIO. On the basis of comparison with NCEP/NCAR reanalysis, strong correlations were found between sea‐salt variations and a quasi‐stationary low that lies to the north of Prydz Bay, SIO. Comparison with a 250‐year‐long summer transpolar index (STPI) inferred from sub‐Antarctic tree ring records reveals strong coherency. Decadal‐scale SLP variability over SIO suggests shifting of the polar vortex. Prominent decadal‐scale deepening of the southern Indian Ocean low (SIOL) exists circa 1790, 1810, 1835, 1860, 1880, 1900, and 1940 A.D., continuously after the 1970s, and prominent weakening circa 1750, 1795, 1825, 1850, 1870, 1890, 1910, and 1955 A.D. The LGB65 sea‐salt record is characterized by significant decadal‐scale variability with a strong ∼21‐year periodic structure (99.9% confidence level). The relationship between LGB65 sea salt and solar irradiance changes shows that this periodicity is possibly the solar Hale cycle (22 years).

Glaciochemical investigation of an ice core from Belukha glacier, Siberian Altai

During summer 2001, a 140 m long ice core was recovered from the Belukha glacier (49°48′26″N, 86°34′43″E, 4062 m a.s.l.) in the Siberian Altai. The englacial temperature of −17°C indicates that this unique glaciochemical record is well preserved and suitable for the reconstruction of air pollution levels in this previously unexplored region. The upper 86 m were dated by 210Pb and cover the period 1862–2001. A lack of strong winter minima was observed in the δ18O record and attributed to the small amount of precipitation during that season and to wind erosion. The ion concentrations are comparable to those observed in Swiss glaciers, except for ammonium and formate, where enhanced concentrations indicate biogenic emissions from Siberian forests. Sulfate, ammonium and nitrate records all show anthropogenic impacts despite the remoteness of this site.

A 100‐year record of North Pacific volcanism in an ice core from Eclipse Icefield, Yukon Territory, Canada

A record of regionally significant volcanic eruptions in the North Pacific over the last century has been developed using a glaciochemical record from Eclipse Icefield, Yukon Territory, Canada. Tephrochronology of the Eclipse ice core provides positive identification of the 1907 Ksudach, Kamchatka, the 1912 Katmai, Alaska, the 1947 Hekla, Iceland, and the 1989 Redoubt, Alaska, eruptions. Non‐sea‐salt SO42− residuals above a robust spline and empirical orthogonal function (EOF) analysis were used to identify volcanic SO42− signatures. Volcanic sulfate values are more conservatively identified by the EOF analysis as sulfate deposition from other sources is more robustly accounted for. Some eruptions are also recorded as peaks in non‐sea‐salt chloride. The volcanic signals in the Eclipse ice core are mostly attributable to Alaskan, Aleutian, or Kamchatkan eruptions. Conversely, the Eclipse ice core provides a poor record of globally significant tropical eruptions. These results are promising for the development of longer ice core based records of paleovolcanism in the North Pacific rim.

Sea level pressure variability in the Amundsen Sea region inferred from a West Antarctic glaciochemical record

Using European Center for Medium‐Range Weather Forecasts (ECMWF) numerical operational analyses, sea ice extent records, and station pressure data, we investigate the influence of sea level pressure variability in the Amundsen Sea region on a West Antarctic (Siple Dome) glaciochemical record. Empirical orthogonal function analysis of the high‐resolution Siple Dome multivariate ice core chemical time series record (SDEOF1) documents lower tropospheric transport of sea‐salt aerosols to the site. During 1985–1994 the SDEOF1 record of high (low) aerosol transport corresponds to anomalously low (high) sea level pressure (SLP) in the Amundsen Sea region. Spatial correlation patterns between ECMWF monthly SLP fields and the annual SDEOF1 record suggest that a majority of sea‐salt aerosol is transported to Siple Dome during spring (September, October, and November). Analysis of zonal and meridional wind fields supports the SLP/SDEOF1 correlation and suggests the SDEOF1 record is sensitive to changes in regional circulation strength. No relationship is found between sea ice extent and the SDEOF1 record for the period 1973–1994. To investigate the SDEOF1 record prior to ECMWF coverage, a spring transpolar index (STPI) is created, using normalized SLP records from the New Zealand and South America/Antarctic Peninsula sectors, and is significantly correlated (at least 95% c.l.) with the SDEOF1 record on an annual (r = 0.32, p < 0.001) and interannual (3 years; r = 0.51, p < 0.001) basis. Dominant periodicities (3.3 and 7.1 years) in the annual SDEOF1 record (1890–1994 A.D.) suggest that a portion of the recorded interannual variability may be related tropical/extratropical ENSO teleconnections. Changes in the periodic structure of the full (850–1994 A.D.) Siple Dome record suggests a shift in SLP forcing during the Little Ice Age (∼1400–1900 A.D.) interval.

Environmental change profiled in Greenland Ice Core Record

The longest continuous high‐resolution record of climate response available in the Northern Hemisphere, covering approximately 250,000 years, is the focus of Union sessions U31D, U32C, and U41B, “Climate from Central Greenland Core Records I, II, and III.” This climate record has been provided by the Greenland Ice Sheet Project 2 (GISP2), which successfully reached bedrock on July 1, and its European‐led counterpart, the Greenland Ice Project (GRIP). Presentations will focus on information obtained from analyses of the over 3,000‐m‐deep ice core samples retrieved by both projects. These analyses cast light on atmospheric and environmental conditions during selected periods and on correlations between selected environmental or atmospheric components and changes in climate in Greenland.P. A. Mayewski and his group will present examples of how important signals extracted from the glaciochemical record provided by the ice core have been developed into paleoenvironmental interpretations of abrupt changes in atmospheric circulation, sea ice distribution, and other environmental boundary conditions during major periods of climate change.