Shallow Ice Core Research Articles

Dating of the Dome Fuji shallow ice core based on a record of volcanic eruptions from AD 1260 to AD 2001

We measured the concentration of non-sea-salt sulfate ( nssSO 4 2 − ) in the Dome Fuji shallow ice core (Antarctica) from the surface to 40 m depth with the aim of dating the core with reference to the record of volcanic eruptions. Three huge spikes related to large-scale volcanic eruptions were detected at depths of 12.5, 29.9, and 38.8 m, correlated to the eruptions of Tambora (AD 1815), Kuwae (AD 1452) and an unknown event (AD 1259), respectively. We identified another nine nssSO 4 2 − spikes related to accurately dated eruption events. The shallow ice core was dated from AD 1260 to AD 2001 based on these 12 eruption events and the assumption of constant annual snow accumulation in the periods between eruption events. The results yield a maximum correction of ∼20 years compared with the dating proposed in a previous study. The annual accumulation varied within ±∼15% of the average water equivalent value over the study period (25.5 mm).

Microscopic analyses of insoluble particles in an ice core of Ürümqi Glacier No. 1: Quantification of mineral and organic particles

Insoluble particle concentration in ice cores is commonly analyzed as a proxy for variations in atmospheric mineral dust (aerosol concentration). However, recent studies have revealed that the mineral dust is not only a constituent of the particles but that biogenic organic particles are also contained. We microscopically analyzed insoluble particles in a shallow ice core drilled on a mountain glacier, the Urumqi Glacier No. 1, in eastern Tienshan, China. We distinguished different morphological particles in the ice core and quantified them separately. Results showed that the insoluble particles in this ice core consisted mainly of mineral particles, amorphous organic particles, pollen, and microorganisms. Mineral particles were the most dominant, accounting for approximately 67% of total particles, and amorphous organic particles were the second most dominant, accounting for approximately 33% of the total. The annual variation in the particles for the last 11 years differed between mineral and amorphous organic particles. The results suggest that the total insoluble particle concentration in the ice core reflects not only the atmospheric mineral dust but also the organic particles blown from ground soil or produced by microbes on the glacial surface.

Reconstruction of Antarctic climate change using ice core proxy records from the coastal Dronning Maud Land, East Antarctica

Antarctic ice core records have provided unprecedented information on past climatic changes and forcing factors on decadal to millennial timescales. The glaciochemical and stable isotope records of a shallow ice core from the coastal Dronning Maud Land (East Antarctica) were used here to reconstruct the coastal Antarctic environmental variability during the past ∼470 years. Sea salt ion data indicate a significant additional contribution of chloride ions compared to sea water values, possibly through atmospheric scavenging. The nitrate (NO3−) profile exhibit significant temporal shifts than that of the sulphate (SO42−), with a major shift around 1750 AD. The changes in NO3− record are synchronous with the proxy record of solar activity (10Be profile from a South Pole ice core), suggesting enhanced NO3− values during periods of reduced solar activity like the Dalton Minimum (∼1790–1830 AD) and Maunder Minimum (∼1640–1710 AD). The δ18O records reveal that the more negative δ18O values were coeval with several events of increased NO3− concentrations, suggesting enhanced preservation of NO3− during periods of reduced air temperatures. The δ18O and δD records of the core also suggest significant short-term and long-tem variability with more negative values indicating relatively lower air temperatures prior to 1715 AD. The δ18O records also revealed a significant warming of 2.7°C for the past 470 years, with a warming of ∼0.6°C per century.

Influence of the Tungurahua eruption on the ice core records of Chimborazo, Ecuador

Abstract. The comparison of two shallow ice cores recovered in 1999 and 2000 from the same place on the Chimborazo summit glacier revealed the influence of the coincident Tungurahua volcanic eruption on their stable isotope and chemical records. The surface snow melting and water percolation induced from the ash deposition caused a preferential elution and re-localization of certain ionic species, while the stable isotope records were not affected. Additionally, the comparison of the ionic amount and some selected ion ratios preserved along the ice core column reports under which processes the chemical species are introduced in the snow pack, as snow flake condensation nuclei, by atmospheric scavenging or by dry deposition. This preliminary study is essential for the interpretation of the deep Chimborazo ice core, or for other sites where surrounding volcanic activity influences the glaciochemical records.

Sr and Nd isotopic composition of dust in Dunde ice core, Northern China: Implications for source tracing and use as an analogue of long-range transported Asian dust

This study presents the Sr and Nd isotopic composition of dust from a shallow Dunde ice core (38°06′N, 96°24′E, 5325 m a.s.l.), Northern China, in order to trace its source regions and the provenance of long-range transported (LRT) Asian dust. Dunde dust samples show similar Sr ( 87Sr/ 86Sr averages 0.719982 and varies between 0.715220 and 0.721874) and Nd (ε Nd(0) averages − 10.6 and ranges from − 11.1 to − 9.9) isotopic composition to desert sand from Taklimakan and Qaidam, revealing that the Tarim and Qaidam Basins are the most possible source areas for Dunde dust, while the contribution from Badain Jaran and Tengger seems very small or unlikely. Our results indicate that materials from Taklimakan can be entrained from the Tarim Basin and transported to Qilian Shan by Westerlies under the present climate. The Sr–Nd isotopic composition of Dunde dust, which is a good analogue for the long-range transported Asian dust, resembles that of North Pacific and Greenland dust, indicating that the important provenance of end members of the Asian dust seems to be Taklimakan on a regional scale.

Nitrate records of a shallow ice core from East Antarctica: Atmospheric processes, preservation and climatic implications

High-resolution records of nitrate (NO3−), oxygen isotope (δ 18O) and non-sea salt sulphate (nssSO42− ) were studied using an ice core collected from central Dronning Maud Land in East Antarctica to identify the influence of environmental variability on accumulation of NO3− over the past 450 years. The results confirmed that multiple processes were responsible for the production and preservation of NO3− in Antarctic ice. Correlation between NO3− and nssSO42− peaks revealed that sulphate aerosols released during major volcanic eruptions might have activated the production of nitric acid, which was scavenged by ion-induced nucleation in polar ice sheets. The correlation between the nitrate and δ18 O records further suggest that enhanced NO3− preservation in the ice occurred during periods of lower atmospheric temperature. Major shifts in the NO3− record of the ice core presently studied and its comparison with 10Be record from a core collected from South Pole suggest that a reduction in solar activity influenced the NO3− accumulation in Antarctica through enhanced production of odd nitrogen species.

Post-coring entrapment of modern air in some shallow ice cores collected near the firn-ice transition: evidence from CFC-12 measurements in Antarctic firn air and ice cores

Abstract. In this study, we report measurements of CFC-12 (CCl2F2) in firn air and in air extracted from shallow ice cores from three Antarctic sites. The firn air data are consistent with the known atmospheric history of CFC-12. In contrast, some of the ice core samples collected near the firn-ice transition exhibit anomalously high CFC-12 levels. Together, the ice core and firn air data provide evidence for the presence of modern air entrapped in the shallow ice core samples that likely contained open pores at the time of collection. We propose that this is due to closure of the open pores after drilling, entrapping modern air and resulting in elevated CFC-12 mixing ratios. Our results reveal that open porosity can exist below the maximum depth at which firn air samples can be collected, particularly at sites with lower accumulation rates. CFC-12 measurements demonstrate that post-drilling closure of open pores can lead to a change in the composition of bubble air in shallow ice cores through purely physical processes. The results have implications for investigations involving trace gas composition of bubbles in shallow ice cores collected near the firn-ice transition.

Major ions composition records from a shallow ice core on Mt. Tanggula in the central Qinghai-Tibetan Plateau

A 32.4 m shallow ice core was recovered from a site at 5743 m above sea level on the Mt. Tanggula in the central Qinghai-Tibetan Plateau in August 2005. A total of 630 samples were analyzed for major ions (Na +, NH 4 +, K +, Mg 2+, Ca 2+, Cl −, SO 4 2 − and NO 3 −) and stable oxygen isotope ratios ( δ 18O). The ion chemistry of the upper 14.5 m, covering the last 55 years, is characterized by mineral dust (HCO 3 −, Ca 2+, SO 4 2 −, Na +, Cl − and K +), anthropogenic species (SO 4 2 −, NH 4 + and NO 3 −) and soil and biogenic emissions (NO 3 − and NH 4 +). Ca 2+ is the dominant cation in the core with a medium value of 33.5 μeq L − 1, accounting for 64.5% of the total cations, and HCO 3 − is the predominant anion, accounting for 80.2% of the total anions. Compared with ice core records from Altai and Himalayas, at the northern and southern margin of the Qinghai-Tibetan Plateau, respectively, major ion concentrations (except SO 4 2 −, NH 4 + and NO 3 −) in Tanggula ice core are much higher due to pronounced regional crustal aerosol inputs. Increasing SO 4 2 − concentrations in the most recent 50 years are attributed to anthropogenic contributions; but mineral dust is still the major sources for SO 4 2 − in the central Qinghai-Tibetan Plateau. The notable relationship between increasing Northern Hemisphere temperature and NO 3 − and NH 4 + concentrations suggests that recent temperature increase in Qinghai-Tibetan Plateau may be enhancing biological activity and associated NO 3 − and NH 4 + emissions from the regional terrestrial ecosystems.

Mapping changing temperature patterns over a glacial moraine using oblique thermal imagery and lidar

Due to access difficulties in active alpine moraine environments, it can be challenging to accurately map and quantify debris cover and ice-core extent. To aid in identifying the presence and extent of ice-cored moraine, a non-invasive method of mapping spatial and temporal moraine temperature patterns using a light detection and ranging (lidar) digital elevation model (DEM) and sequences of oblique thermal imagery was evaluated. A procedure of lidar DEM-based orthorectification of thermal images collected through time from different locations enabled maps of temperature change to be generated and thermal signatures plotted. Although no exposed ice was visible on the moraine slope studied, the presence of shallow ice core beneath the debris-covered surface was inferred in areas of cooler temperatures during daylight solar heating and rapid thermal decay after sunset. It is presumed that this apparent increased heat loss in some areas of the moraine is being used to drive internal melt processes. It is believed that such temporal thermal imaging at high repetition frequency will aid in remotely mapping the presence of buried ice and, with the combination of energy balance data and further field validation, could enable the estimation of debris cover depth.

Dust concentration and flux in ice cores from the Tibetan Plateau over the past few decades

In this paper, we provide the concentrations and fluxes of dust particles (1–30μm diameter), quantitatively calculated, in several shallow ice cores recovered from the northern (Dunde), western (Muztagata), central (Tanggula) and southern (Dasuopu and Everest) parts of the Tibetan Plateau over the past few decades. Dust concentrations from the northern and western Tibetan Plateau are 2–10 times higher, and from the central Tibetan Plateau is five times higher, respectively, than in the southern part. Dust flux in ice cores is highly dependent on mass concentration, but does not necessarily correlate with accumulation. Dust flux in Dunde (about 798μg cm−2 a−1) is 10 times higher, and that in Muztagata (342μg cm−2 a−1) is four times higher, respectively, than the dust flux in the central Himalayas (77–103μg cm−2 a−1). The quantitative assessment of dust flux in ice cores accords with the aerosol optical depth, and both suggest that the general dust transport route is from northwest to southeast over the Tibetan Plateau. Our results reveal the basic properties of upper level tropospheric dust over the Tibetan Plateau, which is useful for the study of the climatic effects of this dust.

The pH value and electrical conductivity of atmospheric environment from ice cores in the Tianshan Mountains

Electrical Conductivity Measurement (ECM) from ice core is a representative index for atmospheric environmental change. The pH value and ECM from three shallow ice cores (each 3.85 m, 231 ice samples total) on Glacier No.1 at the headwater of Urumqi River, Glacier No.48 in Kuitun area, and Miaoergou Glacier in Hami area in the eastern Tianshan Mountains, western China, were measured and analyzed for atmospheric environment records research. Ice core record shows that the changing trend of pH and ECM in three sites in recent years is different: ECM in Kuitun increases with the ice depth change, but ECM in Hami and Urumqi Glacier No.1 ice cores show a decreasing trend. Average ECM value in Hami is much larger than other two sites, just as the dust concentration and ions concentration are also very high in this site. ECM records in all three sites are mainly affected by aerosol mineral dust of Central Asia, and correlative coefficients of ECM and mineral ions such as Ca2+, Mg2+, Na+ are all significantly high. The pH value and ECM are also significantly high correlative coefficients in the eastern Tianshan Mountains. Comparison between the eastern Tianshan Mountains and other sites in western China, and Polar Regions, shows that the difference of ECM can very well reflect the spatial difference of worldwide atmospheric environment.

Mass balance of the Prince of Wales Icefield, Ellesmere Island, Nunavut, Canada

This paper estimates the mass balance of the Prince of Wales Icefield, Ellesmere Island, Canada, averaged over four decades, from measurements of surface mass balance (SMB) and iceberg calving. Shallow ice core net accumulation measurements and annual mass balance stake measurements are used in conjunction with a digital elevation model and knowledge of the location of the dominant moisture source for precipitation over the ice cap to interpolate and extrapolate spatial patterns of SMB across the Prince of Wales Icefield. The contribution of iceberg calving to the mass balance is calculated from estimates of (1) the annual volume of ice discharged at the major tidewater glacier termini and (2) the annual volume loss or gain due to terminus fluctuations. Two different approaches to determining the SMB conclude that the SMB of the ice field is approximately in balance (average equals −0.1 ± 0.4 km3 w.e. a−1, where w.e. means water equivalent) largely because of its proximity to the main year‐round moisture source that is the Smith Sound portion of the North Open Water polynya. Iceberg calving is a highly significant component of mass loss (−1.9 ± 0.2 km3 w.e. a−1) and is sufficient to make the overall mass balance of the ice field averaged over the period 1963–2003 clearly negative (−2 ± 0.45 km3 w.e. a−1, equivalent to a mean‐specific mass balance across the ice field of −0.1 m w.e. a−1). The Prince of Wales Icefield contributes ∼0.005 mm a−1 to global eustatic sea level rise.

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.

Element composition of dust from a shallow Dunde ice core, Northern China

The Dunde ice cap (38°06'N, 96°24'E, with a summit of 5325 m) is situated at the centre of the northern Chinese deserts and receives dust from these regions. Here, we present the trace and rare earth element (REE) compositions of dust extracted from a shallow ice core from the Dunde ice cap, which provide a framework to trace the source of Dunde dust. Trace and REE parameters of Dunde dust show characteristics of a typical eolian deposit, with an average La/Th ratio of 2.6, a Th/U ratio of 3.7, and a strong negative Eu anomaly (0.61). The dirty layers in the ice core section have the same element characteristics as in the clear layers, indicating that the dust in Dunde is well-mixed and has a stable composition. Trace element and REE ratio plots show that Dunde dust has a similar composition to the finer fraction materials in the Taklimakan desert, suggesting that the Tarim Basin might be an important source for Dunde dust under the present circulation, but not favoring a material contribution from Badain Jaran. Our results reveal distinct differences in composition between Dunde dust and Chinese loess materials, which suggests that they have different sources.

Preliminary results of the close-off depth and the stable isotopic records along a 109.91 m ice core from Dome A, Antarctica

A 109.91 m ice core was recovered from Dome A (or Dome Argus), the highest ice feature in Antarctica, during the 2004/05 austral summer by the 21st Chinese National Antarctic Research Expedition (CHINARE-21). Both methane profile along the core and firn densification model calculation suggest that the close-off depth is at about 102.0 m with an ice age about 4200 a. Stable isotopes (δ18O and δD) of the chips samples produced during each run of ice core drilling at Dome A, together with those of the other cores recovered from the eastern inland Antarctica, suggest a relative stable climate with a temperature fluctuation amplitude about ±0.6°C at the eastern inland Antarctica during the late Holocene. The average d-excess (or d =δ D-8δ18O) of 17.1‰ along the Dome A core is probably the highest among the Antarctic inland ice cores, which may be resulted from the kinetic fractionation during the snow formation under an oversaturation condition. Moreover, the increasing trend of d-excess during the late Holocene reflects mainly the migration of the water source area for precipitation at Dome A towards low latitudes. This paper presents the first results of a shallow ice core recovered from the unexplored highest area of the Antarctic ice sheet, providing a background for the proposing deep ice core drilling at Dome A.

GPR reflection profiles of Clark and Commonwealth Glaciers, Dry Valleys, Antarctica

AbstractEnglacial horizons deeper than 100m are absent within 100MHz ground-penetrating radar (GPR) surface profiles we recorded on Clark and Commonwealth Glaciers in the Antarctic Dry Valleys region. Both glaciers show continuous bottom horizons to 280 m, with bottom signal-to-noise ratios near 30 dB. Density horizons should fade below 50 m depth because impermeable ice occurred by 36 m. Folding within Commonwealth Glacier could preclude radar strata beneath about 80 m depth, but there is no significant folding within Clark Glacier. Strong sulfate concentrations and contrasts exist in our shallow ice core. However, it appears that high background concentration levels, and possible decreased concentration contrasts with depth placed their corresponding reflection coefficients at the limit of, or below, our system sensitivity by about 77m depth. Further verification of this conclusion awaits processing of our deep-core chemistry profiles.

Black carbon record based on a shallow Himalayan ice core and its climatic implications

Abstract. A continuous measurement for black carbon (hereafter "BC") in a 40 m shallow ice core retrieved from the East Rongbuk Glacier (hereafter "ERG") in the northeast saddle of Mt. Qomolangma (Everest) provided the first historical record of BC deposition during the past ~50 yrs in the high Himalyas. Apparent increasing trend (smooth average) of BC concentrations was revealed since the mid-1990s. Seasonal variability of BC concentrations in the ice core indicated higher concentrations in monsoon seasons than those in non-monsoon seasons. Backward air trajectory analysis by the HYSPLIT model indicated that South Asia's BC emissions had significant impacts on the BC deposition in the Mt. Qomolangma (Everest) region. The estimated average atmospheric BC concentration in the region was about 80 ng m−3 during 1951–2001. And it was suggested BC emitted from South Asia could penetrate into the Tibetan Plateau by climbing over the elevated Himalayas. A significant increasing trend of the radiative forcing simulated by the SNICAR model appeared since 1990, which even exceeded 4.5 W m−2 in the summer of 2001. It was suggested that this amplitudes of BC concentrations in the atmosphere over the Himalayas and consequently in the ice in the glaciers could not be neglected when assessing the dual warming effects on glacier melting in the Himalayas.

Dating annual layers of a shallow Antarctic ice core with an optical scanner

AbstractThis study tests novel methods for automatically identifying annual layers in a shallow Antarctic ice core (WDC05Q) using images that were collected with an optical scanner at the US National Ice Core Laboratory. A new method of optimized variance maximization (OVM) modeled the density-related changes in annual layer thickness directly from image variance. This was done by using multi-objective complex (MOCOM) parameter optimization to drive a low-pass filtering scheme. The OVM-derived changes in annual layer thickness corresponded well with the results of an independent glaciochemical interpretation of the core. Individual annual cycles in image brightness were then identified by using OVM results to apply a depth-varying low-pass filter and fitting a second-order polynomial to a locally detrended neighborhood. The resulting map of annual cycles agreed to within 1% of the overall annual count of the glaciochemical interpretation. Agreement on the presence of specific annual layer features was 96%. It was also shown that the MOCOM parameter optimization could calibrate the image-based results to match directly the date of a specific volcanic marker.

Viral dynamics in cryoconite holes on a high Arctic glacier (Svalbard)

Viruses are an abundant and dynamic constituent of microbial communities in aquatic ecosystems. In this study we characterized the abundance of viruses associated first with the bottom sediment and overlying water of cryoconite holes and second with shallow ice cores of two different glaciers in Svalbard. Viral abundances were ca. 10–100 times lower than the average for marine and freshwater ecosystems in temperate regions. Virus to bacterium ratios (VBR) (average > 10, range between 0.7 and 74 in the water and ice samples) and a strong positive correlation between viral and bacterial abundance (r = 0.93, p < 0.01, N = 57) indicate that viruses most probably play an important role in controlling bacterial mortality and hence biogeochemical cycling on glaciers. Samples taken along a transect from the glacier ablation area to proglacial ponds in its forefield showed that viral abundance increased in response to a higher host availability, which in turn probably resulted from an increase in temperature and higher mineral levels in the ponds. In a transplantation experiment, viruses from cryoconite holes were incubated with a bacterial community from a proglacial lake. Results from the transplantation experiment showed that viruses from cryoconite holes were able to infect bacteria from proglacial lakes and thus influence biogeochemical cycles across different glacial ecosystems. Our data therefore suggest that viruses in cryoconite holes may be able to infect a broad range of bacterial species.

Dust storm activity over the Tibetan Plateau recorded by a shallow ice core from the north slope of Mt. Qomolangma (Everest), Tibet‐Himal region

Based on a 39.8 m ice core drilled at the East Rongbuk Glacier (27°59′N, 86°55′E 6518 m a.s.l,), north slope of Mt. Qomolangma (Everest), central Himalaya, the changes of dust storm over the Tibetan Plateau (TP) recorded by insoluble particle and its possible connection with the winter (JFM) North Atlantic Oscillation (NAO) are investigated. The results show that the level of dust storm activity exhibits a significant decreasing trend during the past ∼50 years. This may be attributed, at least partly, to a decrease in wind speed over the TP and its surrounding regions. The normalized time series of the winter NAO index shows a significant inverse correlation with the mass concentration of insoluble particle implying a possible connection between the winter NAO and the dust storm activity over the TP.