Two ice cores, covering 1500 years of climatic information, from the summit (5670 meters) of the tropical Quelccaya ice cap, in the Andes of southern Peru, provide information on general environmental conditions including droughts, volcanic activity, moisture sources, temperature, and glacier net balance. The net balance record reconstructed from these cores reflects major precipitation trends for the southern Andes of Peru. These records indicate extended dry periods between 1720 and 1860, 1250 and 1310, and 570 and 610; wet conditions prevailed between 1500 and 1720. Establishing a tropical precipitation record may help explain climatic fluctuations since the tropical evaporation-precipitation cycle is a principal mechanism driving the atmospheric circulation.

AMANDA is a high-energy neutrino telescope presently under construction at the geographical South Pole. In the Antarctic summer 1995/96, an array of 80 optical modules (OMs) arranged on 4 strings (AMANDA-B4) was deployed at depths between 1.5 and 2 km. In this paper we describe the design and performance of the AMANDA-B4 prototype, based on data collected between February and November 1996. Monte Carlo simulations of the detector response to down-going atmospheric muon tracks show that the global behavior of the detector is understood. We describe the data analysis method and present first results on atmospheric muon reconstruction and separation of neutrino candidates. The AMANDA array was upgraded with 216 OMs on 6 new strings in 1996/97 (AMANDA-B10), and 122 additional OMs on 3 strings in 1997/98.

Neutrinos are elementary particles that carry no electric charge and have little mass. As they interact only weakly with other particles, they can penetrate enormous amounts of matter, and therefore have the potential to directly convey astrophysical information from the edge of the Universe and from deep inside the most cataclysmic high-energy regions. The neutrino's great penetrating power, however, also makes this particle difficult to detect. Underground detectors have observed low-energy neutrinos from the Sun and a nearby supernova, as well as neutrinos generated in the Earth's atmosphere. But the very low fluxes of high-energy neutrinos from cosmic sources can be observed only by much larger, expandable detectors in, for example, deep water or ice. Here we report the detection of upwardly propagating atmospheric neutrinos by the ice-based Antarctic muon and neutrino detector array (AMANDA). These results establish a technology with which to build a kilometre-scale neutrino observatory necessary for astrophysical observations.

Airborne radar has detected Ϸ100 lakes under the Antarctic ice cap, the largest of which is Lake Vostok. International planning is underway to search in Lake Vostok for microbial life that may have evolved in isolation from surface life for millions of years. It is thought, however, that the lakes may be hydraulically interconnected. If so, unsterile drilling would contaminate not just one but many of them. Here we report measurements of temperature vs. depth down to 2,345 m in ice at the South Pole, within 10 km from a subglacial lake seen by airborne radar profiling. We infer a temperature at the 2,810-m deep base of the South Pole ice and at the lake of ؊9°C, which is 7°C below the pressure-induced melting temperature of freshwater ice. To produce the strong radar signal, the frozen lake must consist of a mix of sediment and ice in a flat bed, formed before permanent Antarctic glaciation. It may, like Siberian and Antarctic permafrost, be rich in microbial life. Because of its hydraulic isolation, proximity to South Pole Station infrastructure, and analog to a Martian polar cap, it is an ideal place to test a sterile drill before risking contamination of Lake Vostok. From the semiempirical expression for strain rate vs. shear stress, we estimate shear vs. depth and show that the IceCube neutrino observatory will be able to map the three-dimensional ice-flow field within a larger volume (0.5 km 3 ) and at lower temperatures (؊20°C to ؊35°C) than has heretofore been possible. Measurement of Temperature ProfileT hrough a chain of observations, measurements at the AMANDA (Antarctic Muon and Neutrino Detector Array) neutrino observatory in deep ice at the South Pole (1) have provided an impetus for exploration for life in subglacial lakes. As essential steps in the analysis of high-energy neutrino data, Woschnagg et al. (2) measured optical absorption and scattering coefficients as a function of depth in the glacial ice, and Price et al. (3) determined dust concentration and age as a function of depth by using light sources and detectors installed in the ice. To measure temperature as a function of depth, from which the rate of shear of the AMANDA structure could be estimated, the collaboration installed thermistors at depths from 800 m to 2,345 m in boreholes produced with hot-water drilling. We will return to the question of deformation rate later.The temperatures were measured by Omega Engineering (Stamford, CT) 44031 thermistors. The thermistors were cast into plastic molds and attached to each of 20 AMANDA cables at various locations for a total of 59 measurement points. The cables were deployed at times ranging from the 1993-1994 to the 1999-2000 austral seasons. All thermistors were read out in July 2001 by a Hewlett-Packard-3478 multimeter, after dwell times adequately long (1.5-7.5 yr) for recovery of the refrozen ice to ambient temperature. The measurement uncertainty ranged from 0.24°C for the shallowest depths to 0.11°C for the deepest depths.The depths of the thermistors were determined by correlating...

An ice core in south Greenland covering the period 1869 to 1984 was analyzed for oxygen isotopes and chloride, nitrate, and sulfate concentrations. The data show that the "excess" (nonsea-salt) sulfate concentration has tripled since approximately 1900 to 1910 and the nitrate concentration has doubled since approximately 1955. The increases may be attributable to the deposition of these chemical specis from air masses carrying North American and Eurasian anthropogenic emissions.