Ice Cores

Changes in solar activity modulate the galactic cosmic ray flux, and in turn, the production rate of 10Be in the earth's atmosphere. The best archives of past changes in 10Be production rate are the polar ice cores. Key challenges in interpreting these archives ...

Multiple sulfur (δ 34 S sulfate , Δ 33 S sulfate , & Δ 36 S sulfate), nitrogen and oxygen (δ 15 N nitrate & δ 18 O nitrate) and strontium (87 Sr/ 86 Sr) isotope compositions of precipitation collected from Seoul, South Korea were analyzed to study the sources, transportation and deposition of air pollutants in East Asia. The δ 34 S sulfate values (from 1.9 to 14.6‰ with a median of 4.7‰) and the δ 15 N nitrate values (from-2.0 to 13.3‰ with a median of 1.0‰) suggest that fossil fuel use (emission from coal combustion and vehicle exhaust) is a predominant source for sulfur and nitrogen, but other natural sources including biogenic contributions of DMS also add to their total budget. The seasonal variations are observed in δ 34 S sulfate and δ 15 N nitrate values (both higher in winter season), which is likely to result from the increase of coal use for domestic heating in China. The δ 18 O nitrate values also varied seasonally depending on the NO x oxidation pathway, being about 20‰ higher in winter than in summer season. The Δ 33 S sulfate and Δ 36 S sulfate values are not anomalous, showing the absence of MIF signals in precipitation of Seoul. The 87 Sr/ 86 Sr ratio of the precipitation samples range from 0.70988 to 0.71487 with a median of 0.71073, indicating the influence of at least three end-member (silicate dust, carbonate dust and anthropogenic emission). Ionic ratios such as (K + +NH 4 +)/(Ca 2+ +Mg 2+) and Cl-/Na + suggest the overwhelming effect of anthropogenic input rather than carbonate dust on the end-member with lower 87 Sr/ 86 Sr ratios.

We have generated a new high‐resolution record of variations in planktonic foraminiferal oxygen isotopes (δ18O) and Mg/Ca from a sediment core (IMAGES 97‐2141) in the Sulu Sea located in the Philippine archipelago of western tropical Pacific. This record reveals distinct, suborbital‐scale δ18O changes, most notably during Marine Isotope Stage 3 (MIS3) (∼30,000 to 60,000 years B.P.). The amplitudes of these δ18O fluctuations (0.4 to 0.7‰) exceed that which can be attributed to sea level changes and must be due to changes in sea surface conditions. In the same interval, variations in planktonic foraminifera Mg/Ca suggest that suborbital surface ocean temperature variations of 1 to 1.5°C in the Sulu Sea were not in phase with δ18O. Combined, this evidence indicates that the MIS3 millennial δ18O events in the Sulu Sea were primarily the result of changes in surface water salinity, which today is directly related to the East Asian Monsoon (EAM) and its influence on the balance between su...

The Greenland ice core from NorthGRIP (NGRIP) contains a proxy climate record across the Pleistocene–Holocene boundary of unprecedented clarity and resolution. Analysis of an array of physical and chemical parameters within the ice enables the base of the Holocene, as reflected in the first signs of climatic warming at the end of the Younger Dryas/Greenland Stadial 1 cold phase, to be located with a high degree of precision. This climatic event is most clearly reflected in an abrupt shift in deuterium excess values, accompanied by more gradual changes in δ18O, dust concentration, a range of chemical species, and annual layer thickness. A timescale based on multi‐parameter annual layer counting provides an age of 11 700 calendar yr b2 k (before AD 2000) for the base of the Holocene, with a maximum counting error of 99 yr. A proposal that an archived core from this unique sequence should constitute the Global Stratotype Section and Point (GSSP) for the base of the Holocene Series/Epoc...

Speleothem samples such as flowstone, stalagmite and stalactites are one of the important finds at Çatalhöyük, which they have been carried hundreds of kilometers from its source. The "Çatalhöyük Speleothem Project" have been initiated with the aim of investigating Çatalhöyük's speleothems and identifying their provenance. In order to achieve this, speleothem samples at Çatalhöyük have been recognized and documented, and caves around Çatalhöyük have been investigated. Later, both selected Çatalhöyük speleothem and cave samples of flowstone, stalagmite and stalactites have been analysed by ICP-MS to recognize similar trace elements. In addition, the ages of samples have been obtained by U-Th method to find similarities between the Çatalhöyük samples and speleothem deposits from surrounding caves. The comparative results have been used to identify the sources of Çatalhöyük's speleothems.

The "mainstream" climatology (MSC)-i.e. which includes the Intergovernmental Panel on Climate Change (IPCC) community-considers the present day massive release of greenhouse gases into the atmosphere as the main cause of the current global warming trend. The main inference from this stance is that the increase in temperature must occur after the release of greenhouse gases originating from the anthropic activities. However, no scientific evidence has been provided for this basic notion. Earth paleoclimatic records document the antecedence of temperature over CO 2 levels. For the past 65 Ma, the temperature parameter has controlled the subsequent increase in CO 2. This includes the three rapid aberrant shifts and extreme climate transients at 55 Ma, 34 Ma, and 23 Ma [1]. The simple fact of their existence points to the potential for highly nonlinear responses in climate forcing. Whatever these shifts and transients are, CO 2 remains a second order parameter in their evolution through time. Confronted with the past, a suitable response must therefore be given to the unresolved question of whether the CO 2 trends precede the temperature trends in the current period, or not. The assertion that the current global warming is anthropogenic in origin implicitly presupposes a change of paradigm, with the consequence (the increase in CO 2 levels) that occurred in Earth's past being positioned as the cause of the warming for its present day climatic evolution. The compulsory assumption regarding the antecedence of CO 2 levels over the temperature trends is associated with the haziness of the methodological framework-i.e. the paradigm-and tightens the research fields on the likely origins of global warming. The possible involvement of an "aberrant" natural event, hidden behind the massive release of greenhouse gases, has not been considered by the MSC.

Proxies from Greenland ice cores and North Atlantic marine sediment cores document repeated extreme climate swings of a few decades to millennia during the last glacial cycle, including periods of intense ice rafting called Heinrich events (HEs). We have found similar oxygen isotope variations recorded in mixed-layer–and thermocline-dwelling planktonic foraminifera during HEs 0, 1, and 4, suggesting that three foraminiferal taxa calcified their shells at similar temperatures in a homogenized upperwater column. This implies that the surface mixed layer was deeper during HEs. Similar deepening occurred on the northern margin of the ice-rafted–debris belt, implying that these deep mixed layers during HEs were widespread in the region. We suggest that an increase in storminess during HEs intensified the vertical mixing of meltwater from ice rafting in the upper ocean.

Rapid, or abrupt, climate change is regarded as a change in the climate system to a new state following the crossing of a threshold. It generally occurs at a rate exceeding that of the change in the underlying cause. Episodes of rapid climate change abound in the recent geological past (defined here as the interval between the last glacial maximum, dated to approximately 20,000 years ago, and the present). Rapid climate changes are known to have occurred over time periods equal to or even less than a human lifespan: moreover, their effects on the global system are sufficiently large to have had significant societal impacts. The potential for similar events to occur in the future provides an important impetus for investigating the nature and causes of rapid climate change. This paper provides a brief overview of rapid climate change and an introduction to this special issue, which presents results generated by the palaeoclimatic component of the UK Natural Environment Research Council's rapid climate change programme, called RAPID. The papers in the special issue employ palaeoclimatic proxy data-sets obtained from marine, ice core and terrestrial archives to reconstruct rapid climate change during the last glacial cycle, its subsequent termination and the ensuing Holocene interglacial; some papers also report new attempts to match the palaeoclimate data to hypothesised causes through numerical modelling. The results confirm the importance of freshwater forcing in triggering changes in Atlantic meridional overturning circulation (MOC) and the close links between MOC and rapid climate change. While advancing our understanding of these linkages, the RAPID research has highlighted the need for further research in order to elucidate more specific details of the mechanisms involved.

Soil formation is classically regarded as a 'topdown' process whereby soil thickness, horizonation and vertical anisotropy increase steadily (not necessarily linearly) over time. However, where incremental additions to the land surface are common (e .g. loess, tephra, alluvium or colluvium), the process of soil upbuilding becomes important. The degree of soil expression is governed by the relative rates of pedogenesis and aggradation, which are unlikely to remain constant over time (Almond and Tonkin 1999). The interplay between these processes was examined by Johnson and Watson-Stegner (1987) and others. Soils on aggrading landscapes undergo 'developmental upbuilding ' (progressive pedogenesis) if rates of addition allow assimilation of the deposits and profile deepening, or 'retardant upbuilding' (regressive pedogenesis) if rates are so rapid that horizonation is prevented. In upbuilding soils, each increment of soil below the A horizon has experienced proc...

1 University of Gent, Department of Biology, Research group Marine Biology, Campus Sterre, Krijgslaan 281/S8, 9000 Ghent, Belgium E-mail: gabriella_pan@hotmail.it 2 Department of Biology, Faculty of Sciences and Bio-engineering Sciences, Vrije Universiteit Brussel – VUB, Pleinlaan 2, 1050 Brussels, Belgium 3 Ghent University, Department of Biology, Marine Biology Research Group, Campus Sterre S8, Krijgslaan 281, 9000 Gent, Belgium

In this paper that I intend to add to my Sixth Edition of my book The Making, the Rise, and the Future of the Speakingman as its post-scriptum, I attempt to enhance the accuracy of my fundamental hypothesis on which is based this book. The paper contains new arguments and documentation, which intend to provide a more coherent support to the mentioned hypothesis.
I added to this initial two-pages summary another more detailed and updated summary that is seven pages.

The failure to detect C3 in absorption in diffuse clouds (24), however, appears to rule out this attribution. Note added in proof: We recently received a manuscript by R. J. Glinski and J. A. Nuth (27) in which a vibrational band assignment of the 5800 A Red Rectangle emis- sion features to C3 is presented. Combining this assignment with the results described here leads to the conclusion that C3 is the carrier of the X=5797, X=5850, and nearby related diffuse interstellar absorption bands.

Horizontal variation of landfast sea-ice properties was studied in the Gulf of Bothnia, Baltic Sea, during March 2004. In order to estimate their variability among and within different spatial levels, 72 ice cores were sampled on five spatial scales (with spacings of 10 cm, 2.5 m, 25 m, 250m and 2.5 km) using a hierarchical sampling design. Entire cores were melted, and bulk-ice salinity, concentrations of chlorophylla(Chla), phaeophytin (Phaeo), dissolved nitrate plus nitrite (DIN) as well as dissolved organic carbon (DOC) and nitrogen (DON) were determined. All sampling sites were covered by a 5.5–23 cm thick layer of snow. Ice thicknesses of cores varied from 26 to 58 cm, with bulk-ice salinities ranging between 0.2 and 0.7 as is typical for Baltic Sea ice. Observed values for Chla(range: 0.8–6.0 mg ChlaL–1; median: 2.9 mg ChlaL–1) and DOC (range: 37–397 μM; median: 95 μM) were comparable to values reported by previous sea-ice studies from the Baltic Sea. Analysis of variance amo...

The 15 N/ 14 N and 18 O/ 16 O ratios of nitrate in the Greenland Ice Sheet Project 2 (GISP2) (Summit, Greenland) ice core are much higher in ice from the last glacial period than in the pre-industrial Holocene, despite the lack of a significant glacial/interglacial change in nitrate concentration. While both the 15 N/ 14 N and 18 O/ 16 O records are anticorrelated with snow accumulation rate, neither is satisfactorily explained by accumulation changes or post-depositional processes. The similarity in the glacial/ interglacial change in 15 N/ 14 N from several different Greenland ice cores and the large amplitude of this change relative to observed seasonal variation raise the possibility that the isotopes of nitrate in ice cores indicate a large-scale glacial/interglacial change in the isotopic composition of atmospheric NO x . The glacial/interglacial change in 18 O/ 16 O is best explained by a greater contribution of HNO 3 production from hydrolysis of N 2 O 5 , which has implications for reconstruction of past atmospheric oxidant levels. Although isotope effects associated with NO x photochemistry and nitrate scavenging have not been fully characterized, the 15 N/ 14 N data may indicate glacial/interglacial changes in the relative contributions from different natural sources of NO x on a hemispheric or global scale.

Moraine dam failure and Glacial Lake Outburst Flood (GLOF) are phenomena closely related to climate change. These events may cause floods of great magnitudes in the downstream river reaches. More than 61% of GLOFs were initiated by displacement waves from ice avalanches that collapsed into the lakes from hanging or calving glaciers and rock avalanches. However, in-depth knowledge of the mechanism of the dam failures by waves overtopping and measured data are still lacking. Extensive laboratory experiments are carried out to study such type of failure mechanism by varying size of ice/rock avalanche, shape of the dam, dam material and lake water level. The outflow hydrographs produced by waves overtopping and erosion consist multiple peaks. For the same falling block and lake water level, the initial peaks are similar for both triangular and trapezoidal dams. However, magnitude and timing of subsequent peaks are different according to dam shapes and dam materials.

The degree to which Southern Hemisphere climatic changes during the end of the last glacial period and early Holocene (30-8 ka) were influenced or initiated by events occurring in the high latitudes of the Northern Hemisphere is a complex issue. There is conflicting evidence for the degree of hemispheric 'teleconnection' and an unresolved debate as to the principle forcing mechanism(s). The available hypotheses are difficult to test robustly, however, because the few detailed palaeoclimatic records in the Southern Hemisphere are widely dispersed and lack duplication. Here we present climatic and environmental reconstructions from across Australia, a key region of the Southern Hemisphere because of the range of environments it covers and the potentially important role regional atmospheric and oceanic controls play in global climate change. We identify a general scheme of events for the end of the last glacial period and early Holocene but a detailed reconstruction proved problematic. Significant progress in climate quantification and geochronological control is now urgently required to robustly investigate change through this period.

When structures such as oil drilling rigs are constructed on or through the ice plate in coastal and offshore regions, the shear strength of sea ice must be estimated to determine the loading on these structures. Testing methods for shear strength must be established so that shear strength of sea ice in various conditions can be determined.The authors have been conducting, for five years, direct shear strength experiments using sea ice samples from the Okhotsk Sea coast. Physical characteristics of sea ice, including shear strength, depend to a great extent on such properties as salinity, porosity, grain size, etc; thus, there is variation in the test results of five years experimentation since the samples obtained varied from year to year.The following conclusions were drawn from this experiment: i)Under certain conditions the relation between shear strength and vertical stress can be represented by Coulomb’s equation of soil; ie, where Ts: shear strength, C* : apparent cohesion (s...

Coupled measurements of the oxygen isotope and salinity of surface waters at every degree latitude along a transect from India to Antarctica during summer 2010 were carried out to gain insight into the surface hydrological processes active in the Indian and Southern Oceans. It is possible to identify discrete water masses from the Indian and Southern Oceans based on oxygen isotope and salinity. We determine the relationship between oxygen isotope and sea surface salinity (δ 18 O-SSS) pertaining to those distinct water masses by combining our data with those available at the NASA-GISS data center. These relationships are predominantly governed by evaporation/ precipitation except in the Antarctic Zone (beyond Polar Front) where sea ice melting/freezing plays a dominant role. We obtain more representative, long-term mean values of the slopes and intercepts of the salinity-oxygen isotope relation that will help to determine paleosalinity from carbonate fossils from sediments more accurately. The Subtropical and Polar Fronts were identified at 44°S and 54°S, respectively. These new data will also be useful to fill the gap in the existing global gridded δ 18 O data sets obtained by interpolating the observed values.

We describe a first attempt of dendroclimatic field reconstruction, based upon five ringwidth chronologies from living trees, in Japan and Korea. Mean March-May temperature derived from a gridded land air temperature dataset (CRUTEM3) between 35-40 • E and 125-140 • N was reconstructed for the period of 1784-1990 AD. The reconstruction accounted for 19.4 % of the temperature variance in the calibration period. This reconstruction showed remarkably similar fluctuations to regional dendroclimatic reconstructions in Japan and Korea, indicating the past spatial coherency of spring temperatures in the region. The reconstruction was validated against other climate proxies. A fairly good agreement was found with cold periods as estimated from documentary records in China and Japan. The west-Japan temperature series recovered also showed a reasonable agreement with the reconstruction. These comparisons revealed that climatic field reconstruction using tree-ring chronologies in this area offers a good potential for reconstructing long-term and large-scale past temperature patterns for East Asia.

Historical records, recent observations, and geomorphological evidence indicate that rates of retreat and downwasting of the tidewater Stephenson Glacier, and concurrent expansion of ice-marginal melt-lakes, has increased by an order of magnitude since 1987. Melt-lake expansion is partly the product of greatly accelerated ablation of older, ice-cored twentieth-century moraines. The timing of these changes broadly coincides with reported increases in atmospheric and sea-surface temperatures around other sub-Antarctic islands, but correlates less well with changes along the northern Antarctic Peninsula, where warming has been more rapid. These recent changes in landscape character and geomorphological processes have implications for geodiversity, biodiversity, and cultural heritage values in this World Heritage Area. If the causal climatic warming is anthropogenic, it reinforces the fact that even the most remote and littlevisited nature conservation reserves may be compromised by off...

A low-resolution strontium isotopic ratio ( 87 Sr/ 86 Sr) record coupled with a high-resolution Sr concentration profile covering the last deglacial period were obtained for a stalagmite, SJ3, collected from Songjia Cave, northeast Sichuan province, Central China. Both Sr and 87 Sr/ 86 Sr display significant variations during the period between 20 and 10 ka, which correlate well with oxygen isotope records from Greenland ice cores and speleothems in the East Asian summer monsoon regime, with higher Sr and more radiogenic 87 Sr/ 86 Sr values occurring during cold-dry climatic phases and vice versa. The Sr in SJ3 shows a negative linear relationship between 87 Sr/ 86 Sr and 1/Sr, suggesting the binary mixing of two end-members, the host rock of Late Permian limestone with a relatively lower 87 Sr/ 86 Sr ratio (∼ 0.7071) and an exotic Sr source with a relatively radiogenic 87 Sr/ 86 Sr ratio (∼ 0.7109 deduced from the 87 Sr/ 86 Sr-1/Sr correlation). Atmospheric dust activity was suggested to be the most probable factor influencing the two indices. Because the carbonate fraction in wind-blown dust is enriched in Sr and has a more radiogenic 87 Sr/ 86 Sr ratio, enhanced atmospheric dust activity under stronger Asian winter monsoon which is associated with cold-dry climate would lead to higher Sr concentrations and more radiogenic 87 Sr/ 86 Sr ratios in SJ3 and vice versa. This interpretation is supported by the general parallelism of the two Sr indices to winter monsoon proxy from East Asia such as the dust flux and quartz median diameter in Luochuan loess profile during the same period. This study suggests that the speleothem 87 Sr/ 86 Sr ratio and Sr concentration, especially the former in northeastern Sichuan Province can be used to investigate the atmospheric dust activity and Asian winter monsoon.

Climatic factors play an essential role in the growth of tree ring width. In this study, we aimed to evaluate the correlation between climatic variables and tree-ring growth characteristics of Pinus sibirica in Altai mountains, northwestern China. This study being is first of its kind on climate growth analysis of Pinus sibirica in northwestern China. The study showed great potential to understand the species growing under the specific climatic conditions. Total of 70 tree cores collected from three sites in the sampling area, out of which 63 tree cores considered for this study. The effect of climatic variables which was studied include precipitation, temperature and PDSI. Our results showed that Tree Ring Width chronology has a significantly positive correlation with the late winter (March) temperature and significant negative correlation with the July temperatures. A significant correlation was observed with the late summer precipitation whereas no significant relation found with...

High-resolution marine ice core and marine sediment records contain climate proxy data (e.g., sediment lithology, stable isotopes preserverd in foraminifera tests). Studying global climate involves collecting ice and sediment cores from key sites and comparing the response and timing of climate change among sensitive regions. Students will be able to: • Explain the scientific value of long, continuous ice core and marine sediment records from key regions. • Discuss what makes a region climatically sensitive. • Discuss millennial oscillations in global climate and what may cause them.

Oscillations in ice sheet extent during early and middle Miocene are intermittently preserved in the sedimentary record from the Antarctic continental shelf, with widespread erosion occurring during major ice sheet advances, and open marine deposition during times of ice sheet retreat. Data from seismic reflection surveys and drill sites from Deep Sea Drilling Project Leg 28 and International Ocean Discovery Program Expedition 374, located across the present-day middle continental shelf of the central Ross Sea (Antarctica), indicate the presence of expanded early to middle Miocene sedimentary sections. These include the Miocene climate optimum (MCO ca. 17–14.6 Ma) and the middle Miocene climate transition (MMCT ca. 14.6–13.9 Ma). Here, we correlate drill core records, wireline logs and reflection seismic data to elucidate the depositional architecture of the continental shelf and reconstruct the evolution and variability of dynamic ice sheets in the Ross Sea during the Miocene. Dril...

Advances in AMS physics and organic geochemistry have revolutionized our ability to establish absolute chronologies on vertebrate fossils. Highly purified collagen, which provides extremely accurate 14C ages, can be extracted from single bones and teeth as small as 50 mg. Combined with measurement precisions of ±15 to 25 years for ages of < 20,000 yr, the direct AMS 14C technique enables fossil deposits to be chronologically dissected at the level of single animals. Analysis of data from a variety of sites in the United States indicates that most excavation levels (analysis units) as small as 10 cm can be time averaged by several thousand years at a minimum, even with the greatest care in excavation and processing of sediments. Time averaging of this magnitude has important implications for fine-scale paleoecological analysis of faunas, especially when compared to high-resolution climate records like those derived from speleothems, ice cores, or marine cores. To this end, we prop...

Rock glaciers are abundant in the Lahul and Garhwal Himalayas of northern India and the Karakoram Mountains of northern Pakistan. They exhibit morainic and protalus forms and are restricted altitudinally and climatically to sites above approximately 4000 m asl. and regions where annual precipitation is less than 1000 mm. In these areas, morainic rock glaciers are large, usually ) 1 km long, ) 100 m wide and ) 15 m thick. They are advancing over recent fluvial terraces and modern floodplains. The morainic rock glaciers record the advance of ice-cored moraines following retreat of glaciers, likely since the Little Ice Age. These rock glaciers form a major component of the landscape and are important conveyors of debris down valley under the influence of gravity.

Sublimation and melt disturb the environmental information obtained from ice core records in the Andes. In two case studies we demonstrate to what extent these post-depositional processes may remove major parts of the accumulated snow cover. Dark ash layers from the Tungurahua eruption changed the albedo of surface snow on Chimborazo glacier (6268 m, 1 • 30 S, 78 • 36 W, Ecuador) between two ice core drilling campaigns and forced substantial melt. Redistribution and washout of the chemical constituents shifted the concentration profiles obtained in December1999 as compared to an equivalent core drilled in December 2000. The stable isotope records showed that approximately the water equivalent (weq) of an annual layer had melted, and that the percolating melt water penetrated within the firn layer to a depth of at least 16.5 m without refreezing. In the second example, from a site on the dry axis between the tropical and extra-tropical precipitation belts, significant loss of accumulated snow layers occurred by sublimation. A surface experiment at Cerro Tapado glacier (5536 m, 30 • 08 S, 69 • 55 W, Chile) revealed that losses of ≈2 mm weq (≈5 mm snow) per day occurred during the dry period following the 1997/98 El Niño. This loss generally included the entire surface layer enriched in stable isotopes, and thus caused minimal disturbance of the isotopic signature (and hence climatic information) of the net accumulation, yet chemical constituents again experienced considerable changes in concentration. From annual layer counting and direct dating it is obvious that the major part of the accumulated ice on both glaciers is younger than 100 years; however, isotopic and chemical variations at least in the basal ice from Cerro Tapado clearly point to climate conditions different from the recent centuries. This evidence is supported by mass balance considerations derived from a glacier-climate model. The possibility of a third type of disturbance aside from sublimation and melting -in this case a significant hiatus in the environmental chronology -also deserves consideration for other ice core records from this region. Potential disruptions or discontinuities need to be carefully evaluated given the profound changes in climatic and glaciological conditions since the Last Glacial Maximum throughout Holocene times.

An unexpectedly low annual net accumulation (20 cm w.e.a−1) has been inferred from analyses of a firn core extracted from Glaciar Monte San Valentín, Northern Patagonia Icefield (46°35′ S, 73°19′ W; 3747 m a.s.l.). We test a hypothesis linking the low accumulation to a frequent lack of cloud cover over the mountain range at this altitude. The cloudiness over Monte San Valentín and surrounding regions is examined using ∼3000 daily MODIS satellite images from 2000 to 2008. The visual evaluation of the synoptic situation leads to the definition of a daily cloudiness index (EI) for the San Valentín summit and for the regions to the southwest (SW) and northeast (NE). We check its robustness by applying different tests and comparisons. Three levels are assigned for the EI: ‘clear’ (EI = 0), ‘cloudy’ (EI = 1) and ‘mixed’ (EI = 0.5). The results show that the SV cloud cover is similar to the regional cloudiness for more than half the year (54%) and that the case in which the San Valentín su...

Sublimation dominates the ablation process on cold, high‐altitude glaciers in the tropical Andes. Transport of water vapor through the firn and exchange with ambient moisture alter the stable isotope composition of the surface layers. A sublimation experiment carried out during an ice core drilling campaign on Cerro Tapado (5536 m above sea level, 30°08′S, 69°55′W) revealed a strong enrichment in the 2H and 18O content in the surface layer. Concerning the deuterium excess, a decrease occurred at daytime, while during the night, the values remained comparatively constant. At daytime the sublimation is enhanced due to the higher moisture deficit of the ambient air accompanied by relatively high firn surface temperatures. Low surface temperatures at night cause condensation of water vapor in the firn pores near the surface and thus inhibit penetration of the isotopically enriched surface front into deeper firn layers. Measuring an isotope profile obtained through detailed sampling betw...

A new ice core record from the Nevado Illimani (16 ‡S), Bolivia, covers approximately the last 18 000 years BP. A comparison with two published ice records, from Sajama (18 ‡S), Bolivia [Thompson et al., Science 282 (1998) 18581 864] and Huascara ¤n (9 ‡S), Peru [Thompson et al., Science 269 (1996) 46^50], documents a regionally coherent transition from glacial to modern climate conditions in South America north of 20 ‡S. The strong resemblance between the Illimani and Huascara ¤n water isotope records and their differences from the Sajama record, in particular during the period from 9000 years BP to 14 000 years BP, suggest that local water recycling or local circulation changes played a major role for Sajama. We interpret the common Illimani/Huascara ¤n water isotope history in terms of a common change from wetter/cooler conditions during glacial times to drier/warmer conditions in the Early Holocene.

Ice cores and snow pits of the cryosphere contain particles that detail the history of past atmospheric air compositions. Some of these particles result from combustion processes and have undergone long-range transport to arrive in the Arctic. Recent research has focused on the separation of particulate matter from ice and snow, as well as the subsequent analysis of the separated particles for14C with accelerator mass spectrometry (AMS) and for individual particle compositions with laser microprobe mass analysis (LAMMA). The very low particulate concentrations in Arctic samples make these measurements a challenge. The first task is to separate the particles from the ice core. Two major options exist to accomplish this separation. One option is to melt the ice and then filter the meltwater. A second option is to sublimate the ice core directly, depositing the particles onto a surface. This work demonstrates that greater control is obtained through sublimation. A suite of analytical m...

We measured HONO concentrations during a winter field campaign in a suburban site. We compared calculations with measurements and found missing source of HONO. Much higher HONO missing source is found when snow was present at ground. This evidences the existence of a large HONO formation in presence of snow. These findings may significantly affect the photochemistry in urban winter atmosphere.

We propose a noise-assisted tumor-immune system based on the Wiener process. Stochastic sensitivity and chaos both are studied with the variations of noise strengths. The sensitivity analysis is done by confidence ellipsoid fit technique. It indicates that the sensitivity is enhanced with the increase of noise strengths. On finding chaos, the existence of multiperiodicity is investigated by counting periods under the variation of the same noise strengths. Further, noise-induced chaos is quantified by measuring the asymptotic growth of the phase space trajectories. With the same analysis, chaotic and non-chaotic regimes are classified. Moreover, deterministic and its noiseinduced chaotic dynamics are compared using wavelet leader-based multifractal analysis. Numerical results assure that the noise-assisted tumor-immune system illustrates the rich as well as fine structure compared to its non-noisy dynamics.

Two snow and ice cores from the Rennick Glacier area, Antarctica (study area center point lat 71°15ˈS, long 162°30ˈE) were analyzed for the chemical species: chloride, sodium, reactive silicate, sulfate and nitrate. Core E10 (6.35 m) was taken from Evans Névé, a large accumulation basin at the head of Rennick Glacier. Core M1 (4.35 m) was extracted from the accumulation zone on the central plateau of the Morozumi Range, a small mountain massif bordering Rennick Glacier. Cores E10 and M1 span the time periods from 1929 to 1981 and from 1971 to 1981, respectively, as dated using seasonal variations in chloride (E10) and sulfate (M1) concentrations. An estimated net balance of 50 kg m−2 a−1 was derived for site E10 and of 182 kg m−2 a−1 for site M1. The difference in net mass balance may be explained by elevational differences (M1 1400 m a.s.1., E10 2305 m a.s.1.). Recent (1973 to 1980) increases in sodium, silicate and sulfate at site E10 may be linked to decreases in Antarctic pack-i...

We present glaciochemical data from a pilot study of two snow-pits from Quelccaya ice cap, Peruvian Andes. These are the first samples to be analyzed from Quelccaya for nitrate and sulfate by ion chromatography (IC), for nitrate-plus-nitrite, reactive silicate and reactive iron by colorimetry, and for sodium by atomic absorption spectrophotometry. The 3 m pits used in this study represent a one year record of mass accumulation and the 29 samples collected provide the first glaciochemical data from this area which can be compared with glaciochemical studies from other locations. Reactive iron, reactive silicate and sodium, and the profiles of >0.63μm microparticles from Thompson and others (1984) are coincident, suggesting that transport and deposition into this area of each species are controlled by similar processes. The common source is probably local, resulting from crustal weathering. In general, the reactive silicate values are lower than those observed in other alpine glaci...

Results from the first chemistry-transport model study of the impact of the 1783-1784 Laki fissure eruption (Iceland: 64 • N, 17 • W) upon atmospheric composition are presented. The eruption released an estimated 122 Tg(SO 2 ) into the troposphere and lower stratosphere. The model has a high resolution tropopause region, and detailed sulphur chemistry. The simulated SO 2 plume spreads over much of the Northern Hemisphere, polewards of ∼40 • N. About 70% of the SO 2 gas is directly deposited to the surface before it can be oxidised to sulphuric acid aerosol. The main SO 2 oxidants, OH and H 2 O 2 , are depleted by up to 40% zonally, and the lifetime of SO 2 consequently increases. Zonally averaged tropospheric SO 2 concentrations over the first three months of the eruption exceed 20 ppbv, and sulphuric acid aerosol reaches ∼2 ppbv. A total aerosol yield of 51-66 Tg(H 2 SO 4 ) is produced. The mean aerosol lifetime is only 6-9 days, and the peak aerosol loading of the atmosphere is only ∼7 Tg(H 2 SO 4 .2H 2 O). Due to the relatively short atmospheric residence times of both the SO 2 and sulphate, the aerosol loading approximately mirrors the temporal evolution of emissions associated with the eruption. The model produces a reasonable simulation of the acid deposition found in Greenland ice cores. These results appear to be relatively insensitive to the vertical profile of emissions assumed, although if more of the emissions reached higher levels (>12 km), this would give longer lifetimes and larger aerosol yields. This study suggests that most previous estimates of the global aerosol loading associated with Laki have been generally too large in magnitude, and too long-lived. Environmental effects following the Laki eruption may have been dominated by the widespread deposition of SO 2 gas rather than sulphuric acid aerosol.

We present the first estimate of the evolution of tropospheric ozone (O3(T)) radiative forcing since 1860 and into the future. The UKMO 3-D chemistry-transport model (STOCHEM) was used to simulate the tropospheric composition in 1860, 1950, 1970, 1990 and 2100, by changing trace gas emissions. The future scenario used a doubled CO2 climate. STOCHEM includes extensive non-methane hydrocarbon (NMHC) chemistry, and produces a reasonable simulation of present-day O3(T). Radiative forcings caused by the modelled changes in O3(T) since 1860 were calculated using the UKMO radiation code, and included clouds and stratospheric temperature adjustment. Calculated changes in the global annual mean forcing since 1860 were 0.13, 0.22, 0.29 and 0.48 W m -2 for the four years. Up to 1990 this forcing scales linearly with the change in total NOx emissions since 1860; this linearity breaks down in 2100. The 1990 forcing is at the lower end of the range from previous modelling studies (0.28 -0.51 W m -2 ), but is still significant, enhancing the well-mixed greenhouse gas forcing by over 10 %.

Results from the first chemistry-transport model study of the impact of the 1783-1784 Laki fissure eruption (Iceland: 64 • N, 17 • W) upon atmospheric composition are presented. The eruption released an estimated 61 Tg(S) as SO 2 into the troposphere and lower stratosphere. The model has a high resolution tropopause region, and detailed sulphur chemistry. The simulated SO 2 plume spreads over much of the Northern Hemisphere, polewards of ∼40 • N. About 70% of the SO 2 gas is directly deposited to the surface before it can be oxidised to sulphuric acid aerosol. The main SO 2 oxidants, OH and H 2 O 2 , are depleted by up to 40% zonally, and the lifetime of SO 2 consequently increases. Zonally averaged tropospheric SO 2 concentrations over the first three months of the eruption exceed 20 ppbv, and sulphuric acid aerosol reaches ∼2 ppbv. These compare to modelled preindustrial/present-day values of 0.1/0.5 ppbv SO 2 and 0.1/1.0 ppbv sulphate. A total sulphuric acid aerosol yield of 17-22 Tg(S) is produced. The mean aerosol lifetime is 6-10 days, and the peak aerosol loading of the atmosphere is 1.4-1.7 Tg(S) (equivalent to 5.9-7.1 Tg of hydrated sulphuric acid aerosol). These compare to modelled pre-industrial/presentday sulphate burdens of 0.28/0.81 Tg(S), and lifetimes of 6/5 days, respectively. Due to the relatively short atmospheric residence times of both SO 2 and sulphate, the aerosol loading approximately mirrors the temporal evolution of emissions associated with the eruption. The model produces a reasonable simulation of the acid deposition found in Greenland ice cores. These results appear to be relatively insensitive to the vertical profile of emissions assumed, although if more of the emissions reached higher levels (>12 km), this would give longer lifetimes and larger aerosol yields. Introducing the emissions in episodes generates similar results to using monthly mean emissions, because the atmospheric lifetimes are similar to the repose periods between episodes. Most previous estimates of the global aerosol loading associated with

We present the chemistry-climate model UM CAM in which a relatively detailed tropospheric chemical module has been incorporated into the UK Met Office's Unified Model version 4.5. We obtain good agreements between the modelled ozone/nitrogen species and a range of observations including surface ozone measurements, ozone sonde data, and some aircraft campaigns. Four 2100 calculations assess model responses to projected changes of anthropogenic emissions (SRES A2), climate change (due to doubling CO 2 ), and idealised climate change-associated changes in biogenic emissions (i.e. 50% increase of isoprene emission and doubling emissions of soil-NO x ). The global tropospheric ozone burden increases significantly for all the 2100 A2 simulations, with the largest response caused by the increase of anthropogenic emissions. Climate change has diverse impacts on O 3 and its budgets through changes in circulation and meteorological variables. Increased water vapour causes a substantial ozone reduction especially in the tropical lower troposphere (>10 ppbv reduction over the tropical ocean). On the other hand, an enhanced stratosphere-troposphere exchange of ozone, which increases by 80% due to doubling CO 2 , contributes to ozone increases in the extratropical free troposphere which subsequently propagate to the surface. Projected higher temperatures favour ozone chemical production and PAN decomposition which lead to high surface ozone levels in certain regions. Enhanced convection transports ozone precursors more rapidly out of the boundary layer resulting in an increase of ozone production in the free troposphere. Lightning-produced NO x increases by about 22% in the doubled CO 2 climate and contributes to ozone production. The response to the increase of isoprene emissions shows that the change of ozone is largely determined by background NO x levels: high NO x environment increases ozone produc-

►The mineralogy of more than 2300 aeolian dust particles windblown to central East Antarctica (Dome C) during the Holocene was identified ►Disappearance of carbonate dust during the Holocene relates to sea level rise and suppressed deflation from the Argentinean shelf ►Aeolian dust suggests Pampean and Patagonian provenance in the Holocene and a lower latitude contribution, without major circulation changes

Paleoclimate proxy evidence suggests a southward shift of the Intertropical Convergence Zone (ITCZ) during times of Northern Hemisphere cooling, including the Last Glacial Maximum, 19-23 ka before present. However, evidence for movement over the Pacific has mainly been limited to precipitation reconstructions near the continents, and the position of the Pacific marine ITCZ is less well constrained. In this study, we address this problem by taking advantage of the fact that the upper ocean density structure reflects the overlying wind field. We reconstruct changes in the upper ocean density structure during the LGM using oxygen isotope measurements on the planktonic foraminifera G. ruber and G. tumida in a transect of sediment cores from the Western Tropical Pacific. The data suggests a ridge in the thermocline just north of the present-day ITCZ persists for at least part of the LGM, and a structure in the Southern Hemisphere that differs from today. The reconstructed structure is consistent with that produced in a General Circulation Model with both a Northern and Southern Hemisphere ITCZ.

During the austral summer 1996–97 an extensive field program with geophysical and geodetic observations was carried out in the vicinity of the grounding line of Ekstromisen, Dronning Maud Land, Antarctica. The main emphasis of the joint program was placed on continuous observations of the horizontal as well as the vertical component of the ice displacement across the grounding zone. Data-processing methods for the in parts discontinuous time series and the vertical displacements in the area of the grounding zone are described, and first results presented, with the focus on the influence of the ocean tides on grounded ice. Tidal-induced deflections with amplitudes of up to 0.15 m were recorded at a station on grounded ice 1 km from the grounding line.

Conclusion The results of the microscopicas well as of the molecular analysis categorized the meiofauna into two ecotypes which are associated with the ice types (pack ice and fast ice). Figure 3a) Meiofauna composition for 7 ice stations: the abundance of main taxa in individuals per liter b) Chlorophyll a concentration for 7 ice stations in μg per liter c) Ice thickness and snow height for 7 ice stations in meter Figure 4a) Ciliophora composition for pack ice and fast ice in % for two different methods of analyzing b) Meiofauna composition for pack ice and fast ice: the main taxa in relative abundance c) Ice thickness and snow height for pack ice and fast ice in meter Figure 2 Pictures of a) Litostomatea b) Nauplii c) Oligotrichea d) Spirotrichea and e) Phyllopharyngea 2a) b)

This review examines the societal ramifications of large volcanic eruptions— not the proximal impacts of lava, ash, pumice, and gaseous emissions but rather the consequences of the climate forcing triggered by dispersal of volcanic sulfate aerosol in the stratosphere. Using ice core records of volcanism and tree-ring data of summer temperature anomalies, we analyze 38 preindustrial eruptions that injected an estimated 6 Tg or more of sulfur into the stratosphere. We then explore more than 100 works that consider the volcanism-climate-society nexus, teasing out the key elements of their arguments for or against the role of volcanically forced climate change in far-field societal impacts. As well as summarizing and interrogating the history of ideas and state of the art on this topic, we hope to stimulate further holistic, interdisciplinary approaches to assess the broader implications of volcanic eruptions, particularly for global food security—both in the past and in the future.

■ There are compelling arguments to consider the role of volcanically forced climate change in explanations of history.

■ Such research requires integration of geographical, ecological, demographic, econometric, and other data with historical sources and narratives, and therefore demands cross-disciplinary conversation.

■ Statistical evidence is needed to attribute weather and climate extremes to volcanic forcing, and agricultural and pastoral responses to climate anomalies must be reconstructed at high spatiotemporal resolution.

■ Several prominent climate forcing eruptions in circa 304, 1182, 1345, and 1453 CE have hitherto received comparatively little attention.