C44A-01 INVITED 16:00h
WCRP's Climate and Cryosphere (CliC) Project: Climate Change and Middle and Low Latitude Glaciers
The newest World Climate Research Programme (WCRP) Core Project, the Climate and Cryosphere (CliC) Project, is concerned with all aspects of the interactions between the cryosphere and climate. The cryosphere, defined as those portions of the Earth's surface where water exists in solid form, is an integral part of the climate system, both responding to, and influencing climate change. The cryosphere also provides many of the best indicators of climate variability and change. In addition to a range of direct physical indicators (e.g., snow/sea ice/glacier extent and thickness, river and lake freeze-up/break-up dates, etc.), ice cores from glaciers, ice caps and ice sheets have been shown to contain a wealth of information about past climate and environmental conditions. Ice cores are of particular value, since they often come from areas that are remote and poorly observed, yet have a major effect on the climate of the rest of the globe. General Circulation Models (GCMs) usually predict that the Earth's polar regions will warm fastest with the increasing levels of atmospheric greenhouse gases. However, models also indicate that continental interiors should warm more quickly than marine areas at non-polar latitudes. In fact, while some areas in the Arctic and Antarctic have warmed rapidly over the last few decades, it has generally been in the middle and low latitudes that the greatest effects of climate change have been observed. Particularly obvious has been the widespread retreat of glaciers. This retreat, and the warming which it implies, will have not only important scientific consequences but also socio-economic consequences in areas where glacier melt-water is an important component of the water supply. Glaciers preserve records of climate and the environment through both the isotopic composition of the water molecules, and through the chemicals 'trapped' in the snow, firn and ice layers. In polythermal (i.e., cold) glaciers where only limited melt occurs, the isotopic and chemical signals remain largely undisturbed, and ice cores can provide excellent high resolution records of past conditions. In temperate glaciers, where the ice is at its pressure melting point throughout, diffusion processes are much more rapid, and summer melt and run-off can drastically alter the chemical composition. Much of the climatic and environmental information is destroyed. This presentation will discuss the very serious concern that so many middle and low latitude glaciers are retreating and warming. The CliC Project recognizes an urgent need to recover ice cores from all non-polar glaciated regions before warming affects the glaciers and removes the information they contain. Without such information our ability to understand the climate changes that have occurred in the world's mountainous regions will be restricted, and our ability to model and predict future climate will be severely impaired.
C44A-02 INVITED 16:15h
Low-latitude mountain glacier evidence for abrupt climate changes
Clear evidence that a widespread warming of Earth's climate system is now underway comes from low latitude mountain glaciers. Proxy temperature histories reconstructed from ice cores, and the rapidly accelerating loss of both the total ice area and ice volume on a near global scale suggest that these glaciers responding to increasing rates of melting. In situ observations reveal the startling rates at which many tropical glaciers are disappearing. For example, the retreat of the terminus of the Qori Kalis Glacier in Peru is roughly 200 meters per year, 40 times faster than its retreat rate in 1978. Similarly, in 1912 the ice on Mount Kilimanjaro covered 12.1 km$^{2}$, but today it covers only 2.6 km$^{2}$. If the current rate of retreat continues, the perennial ice fields may disappear within the next few decades, making this the first time in the past 11,700 years that Kilimanjaro will be devoid of the ice that shrouds its summit. Tropical glaciers may be considered ``the canaries in the coal mine'' for the global climate system as they integrate and respond to key climatological variables, such as temperature, precipitation, cloudiness, humidity, and incident solar radiation. A composite of the decadally-averaged oxygen isotopic records from three Andean and three Tibetan ice cores extending back over the last two millennia shows an isotopic enrichment in the 20th century that suggests a large-scale warming is underway at lower latitudes. Multiple lines of evidence from Africa, the Middle East, Europe and South America indicate an abrupt mid-Holocene climate event in the low latitudes. If such an event were to occur now with a global human population of 6.3 billion people, the consequences could be severe. Clearly, we need to understand the nature and cause of abrupt climate events.
C44A-03 INVITED 16:30h
The timing and style of Late Quaternary glaciation throughout the high mountains of Central Asia defined by geomorphic, sedimentological, geochronologic and ice core studies
Tibet and the bordering mountains are the most extensively glaciated tract outside the polar regions, exerting an important influence on regional and global environmental change. The glacial system provides water for many hundreds of millions of people in central Asia, and variations in the glacial and associated hydrological systems have profound socio-economic and political consequences. Yet despite the regional and global importance of glaciation in High Asia, the dynamics, extent and timing of Quaternary glaciation in this region are poorly understood and defined. This is partially because of the inaccessibility and vastness of the region, and hence lack of field studies. During recent years, however, numerous ice core and glacial geologic studies have begun to examine some of the more accessible mountain ranges in High Asia to help quantify the nature of Late Quaternary paleoclimatic change in the region. While the new ice core records provide high resolution data defining the magnitude and frequency of climatic oscillations, mainly for the Late Pleistocene and Holocene, the glacial geologic data is enabling reconstructions of the extents of former glaciers to be determined for the last several glacial cycles. Taken together, these data suggest that regional patterns and timing of glaciation throughout the region reflect temporal and spatial variability in the south Asian monsoon and, in particular, regional precipitation gradients, as well as cooling cycles that are broadly associated with Heinrich event. Understanding these patterns of glaciation and the forcing factors are essential for helping to develop and test climatic models that are critical for predicting the likely consequences of global warming on the glaciological and hydrological systems of Central Asia.
C44A-04 INVITED 16:45h
Paleo Environmental Records from Mid-Latitude Ice Cores
Ice core records from mid-latitude glaciers give insight into the atmospheric composition history. One example is the reconstruction of air pollution levels in Europe from Alpine ice cores, showing dramatic increases of anthropogenic emissions starting with the onset of industrialisation in the middle of the 19th century and the reduction in emissions of certain pollutants since regulatory measures were put into effect in the 1970ies. Anthropogenic emissions had a strong impact particularly on the concentrations of various aerosol-related species such as sulphate, nitrate, ammonium, copper, lead, and zinc as well as of carbonaceous particles and radionuclides. Thus, ice core records from mid-latitude glaciers contribute to our understanding of anthropogenic perturbations upon the composition of the atmosphere. This is particularly important in context of aerosol particles with significant climate-forcing potential e.g. sulphate, mineral dust, and carbonaceous particles (including black carbon and organic matter). Because aerosol lifetimes are typically only several days, the global distribution is very inhomogeneous, thus requiring data from many locations to assess the effect on climate.
C44A-05 17:00h
A High Resolution Ice Core Record from the Puruogangri Ice Field, Tibetan Plateau
Three ice cores (215 m, 154 m, and 118 m in length) have been recovered from the Puruogangri Ice Field ($\sim$33\deg$44' $-$ $34\deg$03'N; $\sim$89\deg$00' $-$ $89\deg$20'E; 422.6 km$^{2}$; 5970 masl) on the western end of the Tanggula Mountain Range. The ice bedrock temperature is -$6.2\deg$C. These cores have been continuously analyzed for stable oxygen isotopic ratios, concentrations of major ions and insoluble dust, and total Beta radioactivity. Annual layer thicknesses for the last 41 years reveal an average net annual accumulation 370 mm of water equivalent. The isotopic records from this very remote site indicate that the most significant isotopic enrichment (interpreted as atmospheric warming) in the ice field's history has occurred in the last 50 years. Puruogangri is surrounded by sand dunes that lap onto its margins and as the sand moves in the spring, it produces a distinct annual dust layer that allows precise dating of the cores. Moreover, Puruogangri's vertical relief facilitates the transportation of fragments of the sparse vegetation in the area to the top of the ice field. AMS 14C dating of several plant fragments from near the bottom of the core indicates that the Puruogangri Ice Field formed in the mid-Holocene. The possible reasons will be discussed as to why this high, cold and remote ice field is so young (mid-Holocene).
C44A-06 17:15h
Central Asian Water Cycle Variability over the past Century from Ice-core Isotope Records (Altai, Tien Shan)
The Altai and Tien Shan ice cores records are expanding our understanding of the inter-Hemispheric water cycle and climate dynamics: the moisture advection from Atlantic and Pacific Oceans, and from Aral-Caspian closed drainage basin to the Arctic Ocean defining the interaction over time between the westerly jet stream, and the Asian monsoon, Siberian and Tibetan Highs and deciphering local verses regional change over the temperate and high latitudes. The multi-parameter high-resolution (i.e., sub-seasonal) glacio-climatic and environmental records from the upper fifty meter of the 175 m surface to bottom ice core recovered in 2003 from the Belukha snow-firn plateau at 4115 m (Altai Mts.) and the upper 20 m of the 160 m deep ice-core recovered in 2000 from the head of Inylchek Glacier at 5200 m (Tien Shan Mts.) were developed and evaluated. The long-term meteorological, synoptic, dust storm and forest fire records and physical stratigraphy data were the basis for calibration, validation and interpretation. The mean annual snow accumulation on the Inylchek glacier for the period from 1992 to 1998 was found to be 116 g cm$^{-2}$/yr. Validation of the Altai ice core records through the marker horizon of volcanic eruptions showed monthly accordance in the dating century accumulation ice core records with the mean accumulation rate of 650 g cm$^{-2}$/yr. The $\delta$$^{18}$O, $\delta$D and d excess records showed well-preserved seasonal variation, which is significantly controlled by air temperature, by share of cold/or warm season precipitation amount and origin, transport and recycling of moisture. The $\delta$$^{18}$O-$\delta$D relationship in the upper 50 m of the Altai ice core records has the same slope to the co-variance as that of the global meteoric water line (i.e., 8), while the Tien Shan ice-core records has lower slope (i.e., 7). The snow accumulation of central Asian glaciers was formed from oceanic precipitation and the moisture originated over Aral-Caspian sources. The Northern Atlantic contributed 15% of moisture, while Black and Eastern Mediterranean Seas 32% to the 20 m Inylchek accumulation. The rest precipitation on the Tien Shan glacier has inter-continental origin. The d-excess show means maximum in winter and minimum in summer in both ice-cores records. About 70% of the Altai snow firn core d-excess records vary within 6% and 15% with maximum of more than 40% within the range from 8% to 13% with the shift to higher values in the upper part of ice core pointing on increased share of moisture recycled over intercontinental Asia. More than half of accumulation on the Altai records had Atlantic Ocean origin. Precipitation from the Arctic and Pacific Oceans had the smallest deuterium excess and their share in total accumulation is increasing. Ice core analysis of the composition of $\delta$$^{18}$O reflected different synoptic situations, which will be reconstructed along with air temperature for about the century of ice core records.
http://www.uidaho.edu/~aizen
C44A-07 17:30h
Variation of Biological Activity on a Himalayan Glacier Recovered from a Shallow Ice Core
There is a diverse biological community on the snow and ice surface of glaciers. Recent change of glaciers reported in many parts in the world may affect the biological community on the glaciers. Temporal variation of biological activity on a Himalayan glacier was recovered from a 15 m deep ice core drilled in 1998. The dating showed that the core covers 37 years (1962-98) including the two hiatuses of annual layer. Microscopy revealed that the core contained filamentous cyanobacteria growing on the glacial surface. They discontinuously appeared in mid 1960s, mid 1970s, and 1990s. In particular, the biomass in 1990s is significantly larger than before, indicating their significant bloom in the period. The annual variation of biomass was compared with the variations of dust flux, mass balance, stable isotope, and chemical composition. The comparison suggests that the bloom of the cyanobacteria may be attributed to the combination of climate warming and eutrophication on the glacial surface in 1990s.
C44A-08 17:45h
Testing Environmental Records From Ice Cores of a Temperate Alpine Glacier
Low-latitude temperate alpine glaciers are largely overlooked but potentially useful archives of paleoenvironmental data; although smaller and shorter-lived than polar glaciers, their position adjacent to areas of dense population makes these glaciers attractive research targets. The Palisade Glacier is the largest glacier in the Sierra Nevada, and thus most likely to contain a reasonably unaltered physical and chemical record for the region. We collected two ice cores, ~4-m and 6-m long, from the uppermost bench on the glacier in August, 2003. Subsamples of the ice cores were analyzed for stable isotopes (d18O and dD), trace elemental abundance, and mass-accumulation stratigraphy. In addition, we sampled snow pits near the coring site in early July and early August 2003, and late June 2004 to constrain physical and isotopic changes in the snowpack through the summer meltseason. A SNOTEL site in the same drainage basin provides local records of daily precipitation and temperature, approximately 2000 feet below Palisade Glacier Our results suggest that despite recent thinning, the Palisade glacier preserves both isotopic and elemental stratigraphy. Annual layers are most apparent in the trace element concentrations, which indicate the cores preserve 4-5 years of accumulation, probably from the mid-to late1990's. A heavy concentration of the dust at the surface, combined with snow accumulation records from nearby SNOTEL sites, indicate that all snow from the previous 6 years (since winter of 1997/98, the last above-average snow year in the basin) was lost to ablation. Significantly lower visible dust concentrations in the underlying layers indicate that the core site had net accumulation during the preceding 4 years, in agreement with the SNOTEL record. Stable isotopes co-vary in the cores, coincident with the dust stratigraphy. In addition, the dD/d18O ratios closely resemble the trend of the global meteoric water line, suggesting that post-depositional melting and fractionation have been minimal. These results lend further support to previous studies (e.g., Naftz et al., 1993; Steig et al., 1998) that indicate that small temperate glaciers can preserve valuable, if complex, records of past environmental change. Further coring is needed to confirm our results, and to test viability of deeper ice in this or other glaciers.