Ice accumulation rate in Changme-Khangpu glacier,Sikkim

Vertical profiles of¹³⁷Cs and²¹⁰Pb have been determined in a 9 m column of ice from accumulation zone of Changme-Khangpu glacier in north Sikkim valley.¹³⁷Cs activity varies from 4 to 22 dpm/ L. In many samples²¹⁰Pb occurs at a level of 20 to 65 dpm/ L which is much higher than the expected fallout value.¹³⁷Cs and²¹⁰Pb activities correlate well with each other but not with the dust content. Possibility of²¹⁰Pb production in the nuclear explosions is discussed. Several peaks appear in the depth profile of¹³⁷Cs and²¹⁰Pb which can be matched with Chinese atmospheric nuclear explosions with some phase difference if a uniform ice accumulation rate of 0.7 m per year is assumed since 1969.     

Natural radionuclides in the Arabian Sea and Bay of Bengal: Distribution and evaluation of particle scavenging processes

Vertical and temporal variations in the activities of²³⁴Th,²¹⁰Po and²¹⁰Pb have been measured, in both dissolved and paniculate phases, at several stations in the eastern Arabian Sea and north-central Bay of Bengal. A comparative study allows us to make inferences about the particle associated scavenging processes in these two seas having distinct biogeochemical properties. A common feature of the²³⁴Th profiles, in the Arabian Sea and Bay of Bengal, is that the dissolved as well as total (dissolved + particulate) activity of²³⁴Th is deficient in the surface 200 m with respect to its parent,²³⁸U. This gross deficiency is attributed to the preferential removal of²³⁴Th by adsorption onto settling particles which account for its net loss from the surface waters. The scavenging rates of dissolved²³⁴Th are comparable in these two basins. The temporal variations in the²³⁴Th-²³⁸U disequilibrium are significantly pronounced both in the Arabian Sea and Bay of Bengal indicating that the scavenging rates are more influenced by the increased abundance of particles rather than their chemical make-up. In the mixed layer (0–50 m), the scavenging residence time of²³⁴Th ranges from 30 to 100 days. The surface and deep waters of both the seas show an enhanced deficiency of dissolved²¹⁰Po relative to²¹⁰Pb and that of²¹⁰Pb relative to²²⁶Ra. The deficiencies of both²¹⁰Po and²¹⁰Pb in the dissolved phases are not balanced by their abundance in the particulate form indicating a net loss of both these nuclides from the water column. The scavenging rates of²¹⁰Po and²¹⁰Pb are significantly enhanced in the Bay of Bengal compared to those in the Arabian Sea. The mean dissolved²¹⁰Po/²¹⁰Pb and²¹⁰Pb/²²⁶Ra activity ratios in deep waters of the Bay of Bengal are ∼ 0.7 and 0.1, respectively, representing some of the most pronounced disequilibria observed to date in the deep sea. The Bay of Bengal and the Arabian Sea appear to be the regions of most intense particle moderated scavenging processes in the world oceans. This is evidenced by the gross disequilibria exhibited by the three isotope pairs used in this study.     

Annual fallout of32Si,210Pb,22Na,35S and7Be in rains in India

The concentration of radioisotopes⁷Be,³⁵S were measured in Bombay since 1956 and²²Na,²¹⁰Pb,³²Si since 1963. In Khandala and other stations such measurements have been made at irregular periods since 1961. In addition several measurements especially that of³²Si were made in 1970. Data available todate from Indian stations is summarised and critically analysed. We conclude that appreciable amounts of³⁵S,²²Na and³²Si, over and above their production by cosmic rays, were produced during the high yield Russian tests as evidenced by their fallout between 1962–66. Based on the bomb produced excess the half period for their removal from the stratosphere is deduced to be less than 1 year. The ‘excess’ contribution of³²Si due to bombs is, however, small; about 1% of its inventory in the oceans. The present study shows that for stations where orogeny is the principal mechanism of precipitation, the annual fallout is independent of the annual rainfall.     

Transport and sediment accumulation of210Pb and137Cs in two Southeast Alaskan fjords

Sediment profiles of²¹⁰Pb and¹³⁷Cs in cores collected at increasing distances from the heads of Smeaton Bay and Boca de Quadra fjords indicate that watersheds influence the inventories of radioisotopes present and that the steep topographies of the fjords enhance sediment redistribution. Episodic deposition of terrestrially derived sediment was responsible for roughly 50% of the¹³⁷Cs and 45% of the²¹⁰Pb inventories in shallower (less than 180 m) locations in Wilson and Bakewell arms of Smeaton Bay.²¹⁰Pb sedimentation rates at shallower sites when corrected for episodic deposition were less than sedimentation rates obtained in the deep basins of the fjords where sediment focusing and increased primary productivity in the overlying water column occur. Higher fluxes of dissolved Mn from surficial sediments and subsequent reoxidation in the overlying water may have enhanced scavenging of²¹⁰Pb in basin locations, resulting in higher inventories. Episodic events have occurred frequently in Smeaton Bay and Boca de Quadra suggesting that steady-state conditions with respect to sedimenting particles can be achieved only when averaged over long time periods approaching the time over which¹³⁷Cs and²¹⁰Pb are useful.     

Records of climatic changes and volcanic events in an ice core from Central Dronning Maud Land (East Antarctica) during the past century

The depth profiles of electrical conductance, δ¹⁸O,²¹⁰Pb and cosmogenic radio isotopes¹⁰Be and³⁶Cl have been measured in a 30 m ice core from east Antarctica near the Indian station, Dakshin Gangotri. Using²¹⁰Pb and δ¹⁸O, the mean annual accumulation rates have been calculated to be 20 and 21 cm of ice equivalent per year during the past ∼ 150 years. Using these acumulation rates, the volcanic event that occurred in 1815 AD, has been identified based on electrical conductance measurements. Based on δ¹⁸O measurements, the mean annual surface air temperatures (MASAT) data observed during the last 150 years indicates that the beginning of the 19th century was cooler by about 2‡ C than the recent past and the middle of 18th century. The fallout of cosmogenic radio isotope¹⁰Be compares reasonably well with those obtained on other stations (73‡ S to 90‡ S) from Antarctica and higher latitudes beyond 77‡N. The fallout of³⁶Cl calculated based on the present work agrees well with the mean global production rate estimated earlier by Lal and Peters (1967). The bomb pulse of³⁶Cl observed in Greenland is not observed in the present studies – a result which is puzzling and needs to be studied on neighbouring ice cores from the same region.     

Basal flow rate of Changme-Khangpu glacier,Sikkim Himalaya based on32Si and210Pb chronology

Using environmental radioisotopes silicon-32 and lead-210, the radiometric ages of ice at the surface and at 5 m depth at the snout of the Changme-Khangpu (ck) glacier have been calculated to be 100 and >650 years respectively. Based on i) these age estimates, ii) a net uniform accumulation rate of 0·7 m/yr of ice in the accumulation zone; and iii) applying a simple ice flow model assuming melting of ice of 1 cm/yr at the base of the glacier, it is demonstrated that the average basal flow rate of theck glacier is much smaller (at least by a factor of three) than that of 40 m/yr estimated for the surface ice. This observation is in good agreement with the earlier work on basal flow rates and indicates that the deeper ice near the bed rock travels much slower than the surface ice.     

Middle‐Late Pleistocene Glacial Lakes in the Grand Canyon of the Tsangpo River,Tibet

Many moraines formed between Daduka and Chibai in the Tsangpo River valley since Middle Pleistocene. A prominent set of lacustrine and alluvial terraces on the valley margin along both the Tsangpo and Nyang Rivers formed during Quaternary glacial epoch demonstrate lakes were created by damming of the river. Research was conducted on the geological environment, contained sediments, spatial distribution, timing, and formation and destruction of these paleolakes. The lacustrine sediments 14C (10537±268 aBP at Linzhi Brick and Tile Factory, 22510±580 aBP and 13925±204 aBP at Bengga, 21096±1466 aBP at Yusong) and a series of ESR (electron spin resonance) ages at Linzhi town and previous data by other experts, paleolakes persisted for 691~505 kaBP middle Pleistocene ice age, 75–40 kaBP the early stage of last glacier, 27–8 kaBP Last Glacier Maximum (LGM), existence time of lakes gradually shorten represents glacial scale and dam moraine supply potential gradually cut down, paleolakes and dam scale also gradually diminished. This article calculated the average lacustrine sedimentary rate of Gega paleolake in LGM was 12.5 mm/a, demonstrates Mount Namjagbarwa uplifted strongly at the same time, the sedimentary rate of Gega paleolake is more larger than that of enclosed lakes of plateau inland shows the climatic variation of Mount Namjagbarwa is more larger and plateau margin uplifted more quicker than plateau inland. This article analyzed formation and decay cause about the Zelunglung glacier on the west flank of Mount Namjagbarwa got into the Tsangpo River valley and blocked it for tectonic and climatic factors. There is a site of blocking the valley from Gega to Chibai. This article according to moraines and lacustrine sediments yielded paleolakes scale: the lowest lake base altitude 2850 m, the highest lake surface altitude 3585 m, 3240 m and 3180 m, area 2885 km2, 820 km2 and 810 km2, lake maximum depth of 735 m, 390 m and 330 m. We disclose the reason that previous experts discovered there were different age moraines dividing line of altitude 3180 m at the entrance of the Tsangpo Grand Canyon is dammed lake erosive decay under altitude 3180 m moraines in the last glacier era covering moraines in the early ice age of late Pleistocene, top 3180 m in the last glacier moraine remained because ancient dammed lakes didn’t erode it under 3180 m moraines in the early ice age of late Pleistocene exposed. The reason of the top elevation 3585 m moraines in the middle Pleistocene ice age likes that of altitude 3180 m. There were three times dammed lakes by glacier blocking the Tsangpo River during Quaternary glacial period. During other glacial and interglacial period the Zelunglung glacier often extended the valley but moraine supplemental speed of the dam was smaller than that of fluvial erosion and moraine movement, dam quickly disappeared and didn’t form stable lake.     

210Pb, 226Ra and 32Si in Pavin lake (Massif Central,France)

Measurements of cosmogenic ³²Si and the U-decay series' nuclides ²¹⁰Pb and ²²⁶Ra in waters and sediments of lake Pavin are reported. Both ²¹⁰Pb and ²²⁶Ra are enriched in the anoxic deep waters compared to the oxic surface waters, respectively by a factor of 4 and 10, whereas ³²Si is depleted by a factor of2. Redox conditions in the lake appear to have no marked effect on the ³²Si. Using a steady-state box model it is shown that the deep-water ³²Si concentration is controlled by the underground lacustrine springs. The residence times of ²¹⁰Pb, ³²Si and ²²⁶Ra are1,10 and80 a, respectively. In the case of ³²Si, where more data are available, the assessed inventory data from the overhead atmospheric fallout and that measured in the sediments agree very well as expected. The ²¹⁰Pb- and ³²Si-based deposition rates during the past100 a ranged from 0.8 to 1.9 mm a⁻¹, earlier these were a factor of3–5 faster. The geochemistry of ³²Si and ²¹⁰Pb in lake Pavin in many ways resembles that in the ocean, only the time scales of the processes involved are faster.     

Flow of metals into the global atmosphere

Concentrations of ¹³⁷Cs, ²¹⁰Pb, ²²⁶Ra, U, V, Pb, Cd and Hg have been measured in firn and ice deposited during the past three decades in accumulation zones of glaciers and also in pre-industrial glacier ice collected in Spitsbergen, Northern Norway, Alaska, Southern Norway, Alps, Himalayas, Ruwenzori, Peruvian Andes, and at King George Island in Antarctica. Except for Hg, the geographical distribution of mean concentrations of ²²⁶Ra, U and stable heavy metals in contemporary ice is not uniform, with the lowest concentrations found in Northern Norway, Alaska and Antarctica, and the highest in continental locations at equatorial and middle latitudes. We did not find evidence of changes in rate of metal deposition during the last three decades, as compared with pre-industrial period, however, our samples of pre-industrial ice might be contaminated in part by contemporary fallout migrating from the exposed surface of old parts of glaciers into the deeper ice layers. Using the data on annual injections of ¹³⁷Cs into the global atmosphere and mean global concentrations of radionuclides and heavy metals found in contemporary ice the global annual flows of ²²⁶Ra, ²¹⁰Pb, U,V, Pb, Cd and Hg were estimated as 6.6 kCi, 485 kCi, 12kt, 4870kt, 590 kt, 180 kt and 190 kt, respectively. These estimates are 1–2 orders of magnitude higher than estimates based on primary paniculate emissions. The anthropogenic contribution is a small fraction of the flows, which are dominated by natural processes leading to enrichment of metals in airborne dust.     

Distribution of natural uranium,thorium, lead,and polonium radionuclides in tidal phases of a Delaware salt marsh

Natural radionuclides in the uranium and thorium series were measured in solid tidal phases (suspended particles, bottom sediment, surface microlayer colloids) of a salt marsh in lower Delaware. The purpose was to identify potential processes responsible for trace element cycling (sources, redistribution and exchange) in salt water marshes and with their coastal waters. Generally, concentrations of U, Th,²¹⁰Pb, and²¹⁰Po on the tidal solid phases suggest a general mechanism by which tidal marshes appear to be trapping the nuclides into their interiors. The processes may include transport of enriched fine particles into the marsh, capture by salt marsh grass and chemical fixation by redox processes at the sediment surface. Specifically, the uranium contents of most of the samples are similar with activity ratios²³⁴U²³⁸U≧1, indicating a mixture of detrital and nondetrital (authigenic) uranium inputs such as seawater or ground water. Since the²³⁰Th daughter is generally deficient by about 50%, the authigenic enrichment process appears to favor uranium and is potentially linked to the extensive diagenetic sulfur redox cycle of salt marsh sediments. The²¹⁰Po/²¹⁰Pb activity ratio is less than one on Spartina adsorbed solids, and could suggest a general process in salt marshes which favors²¹⁰Pb enrichment by atmospheric fallout over enrichment of²¹⁰Po on time scales of weeks which correspond to complete tide marsh exchange. A²²⁸Th/²³²Th activity ratio of less than unity on the solids adsorbed onto marsh grass suggests a net process whereby diffusive loss of the intermediate daughter²²⁸Ra from the adsorbed solids to tidal waters dominates over potential²²⁸Th scavenging by suspended sediment.     

Concentrations,physico-chemical states and mean residence times of 210Pb and 210Po in marine and estuarine waters

The concentrations and physico-chemical states of ²¹⁰Pb have been measured in Bikini Atoll and Washington State coastal waters, and ²¹⁰Po in Washington coastal waters. Lead-210 concentrations of 113–133 dpm · m^?3 were found in surface water collections near Bikini Atoll and 29–153 dpm · m^?3 in Bikini Lagoon. The concentrations of ²¹⁰Pb in near Bikini and in Washington State waters increased with depth in the upper 150m at a rate of 0.35–0.45dpm·m^?3 · m^?1. In the North Equatorial Current waters near Bikini Atoll ²¹⁰Pb was found associated predominantly with the soluble (colloidal) fraction, but in Washington coastal waters ²¹⁰Pb and ²¹⁰Po were found associated with the paniculate (> 0.3 μm) fraction. The mean residence times of ²¹⁰Pb, calculated from the atmospheric input to marine waters from precipitation and the concentrations measured in surface water, were consistent with the physico-chemical states of ²¹⁰Pb found in samples collected in deep ocean and coastal waters. Approximate values of the mean residence times were calculated, for the upper 50 m, to be as follows: 58 days in the Strait of Juan de Fuca, 128 days at the 5-mile (8 km) station off Cape Flattery (Washington), 163 days at the 12-mile (19 km) station off Cape Flattery, and 2.6 yr near Bikini Atoll. It appears that ²¹⁰Pb and ²¹⁰Po can be used to trace particle removal rates in the upper layers of marine waters.     

Radionuclide partitioning across great lakes natural interfaces

Several water and surface microlayer samples from Lake St. Clair, the Niagara River, and the North Shore of Lake Ontario collected during 1983–1986 have been assayed for a variety of radionuclides. In addition, the foam accumulating in the pool just below Niagara Falls was also analyzed and found to be the most efficient aqueous phase collector of¹³⁷Cs,²¹⁰Pb, and²²⁶Ra.The order of radioisotope specific activities from highest to lowest is: Lake Ontario sediment, Niagara River suspended solids, Niagara River foam, surface microlayer water, and subsurface water. Radiological dose rates to the sediments from¹³⁷Cs,²²⁶Ra, and²²⁸Th total about 5 mGy/y.     

The maximum Ice Age (LGM) glaciation of the Central- and South Karakorum: an investigation of the heights of its glacier levels and ice thicknesses as well as lowest prehistoric ice margin positions in the Hindukush, Himalaya and in East-Tibet on the Minya Konka-massif

A continuing prehistoric ice stream network between the Karakorum main crest and the Nanga Parbat massive has been evidenced, which, flowing down from the current Baltoro- and Chogolungma glaciers and filling the Shigar valley as well as the Skardu Basin, has flowed together with the Gilgit valley glacier to a joint Indus parent glacier through the Indus gorge. The ice stream network received an influx by a plateau glacier covering the Deosai plateau, which was connected through outlet glaciers to the ice filling of the Skardu Basin and the Astor glacier at the Nanga Parbat, as well as to the lower Indus glacier. The field observations introduced here in part confirm the results as to the Ice Age glacier surface area of Lydekker, Oestreich and Dainelli, but go beyond it. In additon, a reconstruction of the surface level of this ice stream network and its glacier thicknesses up to the highest regions of the present-day Karakorum valley glaciers has been carried out for the first time. In the area under investigation the Karakorum ice stream network showed three ice cupolas, culminating at an altitude of 6200–6400 m. Between the mountain groups towering 1000–2000 m higher up, they communicated with each other over the transfluence passes in a continuous glacier surface without breaks in slope. In the Braldu- and Basna valley ice thicknesses of 2400–2900 m have been reached. In the Skardu Basin, where the glacier thickness had decreased to c. 1500–1000 m, the ELA at an ice level of 3500-3200 m asl had fallen short to the extent that from here on down the Indus glacier a surface moraine cover has to be suggested. However, 80% of the surface of the ice stream network was devoid of debris and had an albedo of 75-90%. The lowest joint glacier terminus of the ice stream network was situated - as has already been published in 1988 – in the lower Indus valley at 850–800 m asl. The reconstructed maximum extension of the ice stream network has been classified as belonging to the LGM in the wider sense (60–18 Ka BP). Four Late Glacial glacier positions (I–IV), with a decreasing ice filling of the valleys, have been differentiated, which can be locally recognized through polish lines and lateral moraine ledges. The valley (trough-) flanks with their ground moraine covers, oversteepened by glacier abrasion, have been gravitationally destroyed by crumblings, slides and rock avalanches since the deglaciation, so that an interglacial fluvial-, i.e. V-shaped valley relief has been developed from the in part preserved glacial relief. The contrast of the current morphodynamics with regard to the preserved forms is seen as an indication of the prehistorically completely different - namely glacigenic – valley development and the obvious rapidity of this reshaping at still clearly preserved glacial forms provides evidence of their LGM-age. In an additional chapter the lowest ice margin positions, so far unpublished, are introduced, which have been reconstructed for the Hindukush, Central Himalaya and on the eastern margin of Tibet.     

Determination of diffusion coefficients associated with the transport of210Pb radionuclides in lake bed sediments

An iterative least-squares optimization technique is utilized in conjunction with a one-dimensional representation of the mass transport equation to generate theoretical²¹⁰Pb concentration/depth profiles beneath the water-sediment interface that are best-fit approximations to directly measured²¹⁰Pb concentration/depth profiles at various locations within the Great Lakes system. The outputs of such an optimization analysis are the diffusion coefficientsD _M (molecular) andD _B (bioturbation) associated with the transport of²¹⁰Pb radionuclides in lake bed sediments. For all stations studied, the estimated values ofD _B are consistently larger than the estimated values ofD _M , emphasizing the importance of accounting for the effects of bioturbation in the modelling of contaminant transport through lake bed sediments.     

念青唐古拉山扎当冰川冰储量估算及冰下地形特征分析

冰川体积估算对水资源以及冰川变化研究具有重要的意义. 但是实测的冰川厚度数据十分稀少,限制了冰川体积的估算. 2011年5月对念青唐古拉山北坡扎当冰川进行了雷达测厚工作,获取了该冰川的厚度分布状况. 基于该冰川的厚度数据,测量点的GPS数据,1970年的地形图和2010年Landsat TM影像,在ArcGIS技术的支持下,采用简单Kriging插值方法对冰川非测厚区域的厚度进行了插值计算,绘制出了冰川厚度等值线图并估算了冰川的冰储量. 结果表明：冰川最大厚度出现于海拔约5 748 m靠近主流线的位置,最大冰厚度为108 m,冰川平均厚度为38.1 m,2010年冰川面积为1.73 km²,扎当冰川的冰储量为0.066 km³. 将扎当冰川表面DEM与冰川厚度分布图相结合,绘制出了该冰川的冰床地形图. 结果显示,在冰川厚度大的区域,冰床地形呈现近V字形分布,这与其相对平缓的冰面地形形成明显对比;同时,在冰表地形较陡区域,冰川厚度不大,冰床地形呈现U形分布.     

Ice thickness,volume and subglacial topography of Urumqi Glacier No. 1, Tianshan mountains,central Asia,by ground penetrating radar survey

The results of radar survey for three times are presented, aiming to determine ice thickness, volume and subglacial topography of Urumqi Glacier No. 1, Tianshan Mountains, central Asia. Results show that the distribution of ice is more in the center and lesser at both ends of the glacier. The bedrock is quite regular with altitudes decreasing towards the ice front, showing the U-shaped subglacial valley. By comparison, typical ice thinning along the centerline of the East Branch of the glacier was 10–18 m for the period 1981–2006, reaching a maximum of ～30 m at the terminus. The corresponding ice volume was 10296.2 × 10 ⁴ m ³, 8797.9 × 10 ⁴ m ³ and 8115.0 × 10 ⁴ m ³ in 1981, 2001 and 2006, respectively. It has decreased by 21.2% during the past 25 years, which is the direct result of glacier thinning. In the same period, the ice thickness, area and terminus decreased by 12.2%, 10.3%, and 3.6%, respectively. These changes are responses to the regional climatic warming, which show a dramatic increase of 0.6°C (10 a) ^?1 during the period 1981–2006.     

Posteruption glacier development within the crater of Mount St. Helens, Washington, USA

The cataclysmic eruption of Mount St. Helens on May 18, 1980, resulted in a large, north-facing amphitheater, with a steep headwall rising 700 m above the crater floor. In this deeply shaded niche a glacier, here named the Amphitheater glacier, has formed. Tongues of ice-containing crevasses extend from the main ice mass around both the east and the west sides of the lava dome that occupies the center of the crater floor. Aerial photographs taken in September 1996 reveal a small glacier in the southwest portion of the amphitheater containing several crevasses and a bergschrund-like feature at its head. The extent of the glacier at this time is probably about 0.1 km². By September 2001, the debris-laden glacier had grown to about 1 km² in area, with a maximum thickness of about 200 m, and contained an estimated 120,000,000 m³ of ice and rock debris. Approximately one-third of the volume of the glacier is thought to be rock debris derived mainly from rock avalanches from the surrounding amphitheater walls. The newly formed Amphitheater glacier is not only the largest glacier on Mount St. Helens but its aerial extent exceeds that of all other remaining glaciers combined.     

Glacier volume estimation from ice-thickness data,applied to the Muz Taw glacier,Sawir Mountains,China

In this work, ground penetrating radar (GPR) data, global position system (GPS) data, Landsat remote sensing images and digital elevation model (DEM) SRTM were used to study the Muz Taw glacier in the Sawir Mountains. By a variety of interpolation methods, spatial pattern of thickness of the Muz Taw glacier was obtained. The results show that there are obvious differences between the available GPR transverse profiles. The lower transverse profile has typical “U”-type topographic feature, the maximum glacier thickness is up to 116.4 m; glacier thickness distribution in the higher profile is relatively flat, with an average about 70–90 m. The longitudinal profile forms a ladder-like distribution, which in the middle of the ice bedrock topography has obvious depression. The average longitudinal ice thickness is about 80.89 m; the maximum ice thickness is up to 122.61 m. In addition, the preliminary estimation of the average thickness and total terminus ice volume were approximately 60.5 m and 0.195 km³, respectively.     

Re-examination on the climatological significance of the ice core δ18O records from No. 1 glacier at the head of Ürümqi River

Ice core δ¹⁸O records from the No. 1 glacier at the head of the ürümqi River were used to characterize the relationship between δ¹⁸O and contemporaneous surface air temperature (Ta) nearby the Daxigou Meteorological Station (3539 m above sea level, ∼2km away from the ice core drilling site). Although the ice core records of annually averaged δ¹⁸O are positively correlated with contemporaneous surface air temperature, especially summer air temperature, the correlation is less significant than that for the precipitation samples due to depositional and post-depositional modification processes. However, the climatological significance of the ice core δ¹⁸O records can be still preserved to a certain degree, which might extend the application of high altitude and sub-tropical ice core δ¹⁸O records to paleoclimate reconstruction.     

Lateglacial and early Holocene palaeoclimatic reconstruction based on glacier fluctuations and equilibrium‐line altitudes at northern Folgefonna,Hardanger, western Norway

Northern Folgefonna (c. 23 km²), is a nearly circular maritime ice cap located on the Folgefonna Peninsula in Hardanger, western Norway. By combining the position of marginal moraines with AMS radiocarbon dated glacier‐meltwater induced sediments in proglacial lakes draining northern Folgefonna, a continuous high‐resolution record of variations in glacier size and equilibrium‐line altitudes (ELAs) during the Lateglacial and early Holocene has been obtained. After the termination of the Younger Dryas (c. 11 500 cal. yr BP), a short‐lived (100–150 years) climatically induced glacier readvance termed the ‘Jondal Event 1’ occurred within the ‘Preboreal Oscillation’ (PBO) c. 11 100 cal. yr BP. Bracketed to 10 550–10 450 cal. yr BP, a second glacier readvance is named the ‘Jondal Event 2’. A third readvance occurred about 10 000 cal. yr BP and corresponds with the ‘Erdalen Event 1’ recorded at Jostedalsbreen. An exponential relationship between mean solid winter precipitation and ablation‐season temperature at the ELA of Norwegian glaciers is used to reconstruct former variations in winter precipitation based on the corresponding ELA and an independent proxy for summer temperature. Compared to the present, the Younger Dryas was much colder and drier, the ‘Jondal Event 1’/PBO was colder and somewhat drier, and the ‘Jondal Event 2’ was much wetter. The ‘Erdalen Event 1’ started as rather dry and terminated as somewhat wetter. Variations in glacier magnitude/ELAs and corresponding palaeoclimatic reconstructions at northern Folgefonna suggest that low‐altitude cirque glaciers (lowest altitude of marginal moraines 290 m) in the area existed for the last time during the Younger Dryas. These low‐altitude cirque glaciers of suggested Younger Dryas age do not fit into the previous reconstructions of the Younger Dryas ice sheet in Hardanger. Copyright © 2005 John Wiley & Sons, Ltd.