Amount Of Meltwater Research Articles

Snow as a contributor to spring flooding in Belarus.

There are some peculiarities in instrumental observation over snow cover characteristics in Belarus and those of neighboring countries. Maximum snow water equivalent varies around Belarus from 107mm in Brest to 207mm in Novogrudok. It differs significantly in terms of years, which is proved by high values of variation coefficients (Cv). Maximums are observed in the south and south-west of Belarus. Minimum values are typical for central and north-eastern parts of Belarus with a stable snow cover. There is a distinct correlation between snow water equivalent and the stations' altitude. We observe a space-time variability of SWE in Belarus' river catchments. Changes in SWE are of cyclic nature. They correlate with current climate fluctuations. In certain parts of Belarus, there is a trend in reduction of SWE up to 8-10mm in 10years. This research determines the amount of water that forms spring flood runoff in the catchments of Belarus' big rivers. Possible daily snow melting is calculated in the research as well. It reaches 26mm in its maximum and 5-6mm on average. The amount of river runoff water, which is formed within Belarus, is 58km3. The amount of melt water is 11km3, which accounts for 19%. In particularly extreme years, melt water reaches 29km3, which is over a half of all annual river runoff.

Importance of cryosphere water resources to China’s socio-economy: Based on multi-level basins analysis

Cryosphere water resources (CWR) play indispensable roles in ecological security and socio-economic development in cold and arid regions of the world. The amount of melt water will continue to decrease once it reaches the maximum (peak water) due to climate change, while the sustainable and rapid development of socio-economy puts higher demand for water resources, which causes an increasing risk of regional water shortage. Therefore, a national assessment on the relationship between CWR and socio-economy is notable. The supply and demand of CWR are linked at the river basin scale, although the upper, middle and lower reaches of the river vary in the contribution of CWR to water availability. Here we analyze the spatial distribution characteristics of China’s CWR and the spatial-temporal patterns of population and GDP in cryosphere-fed-areas (CFA) at three-level basins scale. Then we present an Importance Index, which ranks all basins in terms of their water-supplying role and the downstream dependence of socio-economy. We conclude that: (1) CFA covers 7 primary basins, 38 secondary basins and 84 tertiary basins in China. (2) The top three with large glacier reserves are Tarim River, Qiangtang Plateau and the Yalu Tsangpo River Basin. Central Tibetan Plateau and the Songhua River Basin have high permafrost coverage. Songhua River Basin, northern Xinjiang and the southwest of the Tibetan Plateau have large average snow depth. (3) In 2015, population and GDP in CFA are about 263 million and 11.4 trillion yuan respectively, accounting for 23.1% and 16.5% of the total China, mainly distribute in the southeast and north of the boundary of the first and second steps and the north of the third step of topography of China. From 1995 to 2015, the proportion of population in the CFA increased from 24.4% to 26.8%, while the proportion of GDP in the whole country decreased from 21% to 19%. (4) For the CFA, the larger the socio-economic amounts, the higher the importance of water resources. However, the amount of water supply does not completely match the socio-economic distribution. Although the cryosphere water resources are abundant in the southwest of Tibetan Plateau, the socio-economic demand is small, representing a lower water service there. We have noticed that at the secondary basin scale, 26.8% of people were populated in the CFA, and nearly one-fifth (19%) of economic activities took place there in 2015. This indicates a lager dependence on CWR in socio-economy, especially in the arid northwest China. These conclusions quantitatively support the previous understanding. However, the multi-scale method we used can analyze the small watershed deeply. For example, the Huntai River Basin are of great importance due to its high water supply and demand index, which is conducive to guiding the optimal allocation of water resources and a deep understanding of the importance of water resources.

Accurate Simulation of Ice and Snow Runoff for the Mountainous Terrain of the Kunlun Mountains, China

While mountain runoff provides great potential for the development and life quality of downstream populations, it also frequently causes seasonal disasters. The accurate modeling of hydrological processes in mountainous areas, as well as the amount of meltwater from ice and snow, is of great significance for the local sustainable development, hydropower regulations, and disaster prevention. In this study, an improved model, the Soil Water Assessment Tool with added ice-melt module (SWATAI) was developed based on the Soil Water Assessment Tool (SWAT), a semi-distributed hydrological model, to simulate ice and snow runoff. A temperature condition used to determine precipitation types has been added in the SWATAI model, along with an elevation threshold and an accumulative daily temperature threshold for ice melt, making it more consistent with the runoff process of ice and snow. As a supplementary reference, the comparison between the normalized difference vegetation index (NDVI) and the quantity of meltwater were conducted to verify the simulation results and assess the impact of meltwater on the ecology. Through these modifications, the accuracy of the daily flow simulation results has been considerably improved, and the contribution rate of ice and snow melt to the river discharge calculated by the model increased by 18.73%. The simulation comparison of the flooding process revealed that the accuracy of the simulated peak flood value by the SWATAI was 77.65% higher than that of the SWAT, and the temporal accuracy was 82.93% higher. The correlation between the meltwater calculated by the SWATAI and the NDVI has also improved significantly. This improved model could simulate the flooding processes with high temporal resolution in alpine regions. The simulation results could provide technical support for economic benefits and reasonable reference for flood prevention.

Abiotic Changes Driving Microphytoplankton Functional Diversity in Admiralty Bay, King George Island (Antarctica)

Environmental gradients can provide habitat-specific scenarios for community functional diversity that determine the composition of populations on both spatial and temporal scales. The western shelf of the Antarctic Peninsula has experiencing increasing air temperatures while the climate is transitioning to a warm-humid sub-Antarctic-type of climate. As a consequence, abiotic changes are leading to alterations in the trophic web. Microphytoplankton functional diversity was analyzed across environmental gradients of sea surface temperature, salinity, meltwater percentage and nutrient availability in Admiralty Bay, South Shetland Islands, Western Antarctic Peninsula. Samples were collected during the austral summer from 2009 to 2011 and from 2013 to 2015, at Admiralty Bay for which functional diversity indices were calculated based on species traits. The amount of meltwater (MW) present in Admiralty Bay groups microphytoplankton into communities according to physiological and ecological tolerances, thus leading to a greater functional diversity. When meltwater dominated the bay (> 2.25% MW scenarios iii - 2013-14 and iv - 2014-15), diatoms and dinoflagellates were codominant. An increase in the dinoflagellate fraction of microphytoplankton can be considered a trigger for changes in the structure of the Antarctic food web. Our results suggest using Admiralty Bay as a model for studies on changes in microphytoplankton community composition and functional diversity.

Role of discrete water recharge from supraglacial drainage systems in modeling patterns of subglacial conduits in Svalbard glaciers

Abstract. As the behavior of subglacial water plays a determining role in glacier dynamics, it requires particular attention, especially in the context of climate warming, which is increasing ablation and generating greater amounts of meltwater. On many glaciers, water flowing from the glacier's surface is the main source of supply to the subglacial drainage system. This system is largely influenced by the supraglacial drainage system, which collects meltwater and precipitation and rapidly delivers it to discrete points in the glacier bed via moulins and crevassed areas, called water input areas (WIAs). Models of patterns of subglacial conduits mainly based on the hydrological potential gradient are still regularly performed without taking into account the supraglacial drainage system. We modeled the pattern of subglacial channels in two glaciers located in Svalbard, the land-terminating Werenskioldbreen and the tidewater Hansbreen during the 2015 melt season. We modeled a spatial and a discrete water recharge in order to compare them. First, supraglacial catchments were determined for each WIA on a high-resolution digital elevation model using the standard watershed modeling tool in ArcGIS. Then, interpolated water runoff was calculated for all the main WIAs. Our model also accounts for several water pressure conditions. For our two studied glaciers, during the ablation season 2015, 72.5 % of total runoff was provided by meltwater and 27.5 % by precipitation. Changes in supraglacial drainage on a decadal timescale are observed in contrast to its nearly stable state on an annual timescale. Nevertheless, due to the specific nature of those changes, it seems to have a low impact on the subglacial system. Therefore, our models of subglacial channel are assumed to be valid for a minimum period of two decades and depend on changes in the supraglacial drainage system. Results showed that, for Svalbard tidewater glaciers with large crevassed areas, models of subglacial channels that assume spatial water recharge may be somewhat imprecise but are far from being completely incorrect, especially for the ablation zone. On the other hand, it is important to take discrete water recharge into account in the case of land-terminating Svalbard glaciers with limited crevassed areas. In all cases, considering a discrete water recharge when modeling patterns of theoretical subglacial channels seems to produce more realistic results according to current knowledge.

Climate change vs. socio-economic development: understanding the future South Asian water gap

Abstract. The Indus, Ganges, and Brahmaputra (IGB) river basins provide about 900 million people with water resources used for agricultural, domestic, and industrial purposes. These river basins are marked as “climate change hotspots”, where climate change is expected to affect monsoon dynamics and the amount of meltwater from snow and ice, and thus the amount of water available. Simultaneously, rapid and continuous population growth as well as strong economic development will likely result in a rapid increase in water demand. Since quantification of these future trends is missing, it is rather uncertain how the future South Asian water gap will develop. To this end, we assess the combined impacts of climate change and socio-economic development on the future “blue” water gap in the IGB until the end of the 21st century. We apply a coupled modelling approach consisting of the distributed cryospheric–hydrological model SPHY, which simulates current and future upstream water supply, and the hydrology and crop production model LPJmL, which simulates current and future downstream water supply and demand. We force the coupled models with an ensemble of eight representative downscaled general circulation models (GCMs) that are selected from the RCP4.5 and RCP8.5 scenarios, and a set of land use and socio-economic scenarios that are consistent with the shared socio-economic pathway (SSP) marker scenarios 1 and 3. The simulation outputs are used to analyse changes in the water availability, supply, demand, and gap. The outcomes show an increase in surface water availability towards the end of the 21st century, which can mainly be attributed to increases in monsoon precipitation. However, despite the increase in surface water availability, the strong socio-economic development and associated increase in water demand will likely lead to an increase in the water gap during the 21st century. This indicates that socio-economic development is the key driver in the evolution of the future South Asian water gap. The transgression of future environmental flows will likely be limited, with sustained environmental flow requirements during the monsoon season and unmet environmental flow requirements during the low-flow season in the Indus and Ganges river basins.

Using δ18O as a Tracer of the Formation of Water Masses in the Laptev Sea. Part 1. Quantification of Ice Formation and Melting

Data on salinity and δ18O from the NASA open-source database are used to estimate the Laptev Sea water mass transformation during ice formation and melting. The indicator of these processes is salinity variation. The estimates for the Laptev Sea show that the amount of meltwater can reach 40% for the sea water with salinity below 7 psu. In this case, sea water salinity reduction due to the meltwater inflow alone can be equal to 0.2-0.7 psu. In the sea water with salinity above 7 psu, ice formation prevails over ice melting. This process is the most strongly pronounced in the range of sea water salinity from 15 to 25 psu. In this salinity range, the average water removal for the ice formation makes up 9% (the maximum is 24%), and the average salinity growth is 0.5 psu (the maximum is 1.7 psu). The most transformed sea water masses during ice formation are located in the bottom layer of the shallow southern and southeastern parts of the Laptev Sea, where the sea depth is not more than 50 m.

Genesis of hummocks found in tunnel valleys: an example from Hörda, southern Sweden

In the south-central sector of the former Fennoscandian Ice Sheet, imprints of the sub-glacial hydrological system are present as “glaciofluvial corridors,” formed by glacial meltwater at the ice–bed interface during the Bølling–Allerød warm period. Many of these are interpreted as tunnel valleys and are commonly characterized by hummocks on their valley floors. Contemporary ice sheets produce increased amounts of meltwater as a consequence of global warming, and occasionally it is observed that meltwater is suddenly released from supra- and subglacial lakes, suggesting a highly dynamic subglacial hydraulic system. Studies of the imprints and deposits from such systems on formerly glaciated terrain can expand our knowledge of ice-sheet response to increased meltwater production. Here, we study sediments exposed in two hummocks within the tunnel valley at Hörda, south Sweden. One of the investigated hummocks is superposed by a small esker. This hummock consists of a diamict interpreted as a subglacial traction till, observed to be overlain by esker sediment. A second hummock displays deformed sediment at its base, which is glaciotectonically intercalated with above-lying diamict, a sub-glacial traction till. The sub-till sediments, interpreted as proglacial outwash, were deformed by overriding ice. The sediment was dated using optically stimulated luminescence (OSL), inferring a late MIS 4 or early MIS 3 age, congruent with other observations of sub-till sediments in south Sweden. The investigated hummocks on the floor of the Hörda tunnel valley are interpreted to have been formed by sub-glacial fluvial erosion simultaneous with tunnel valley formation, most probably during the latest deglaciation of the area.

Evolution of the deep Atlantic water masses since the last glacial maximum based on a transient run of NCAR-CCSM3

During the last deglaciation (from approximately 21 to 11 thousand years ago), the high latitudes of the Atlantic Ocean underwent major changes. Besides the continuous warming, the polar and subpolar ocean surface received a large amount of meltwater from the retracting ice sheets. These changes in temperature and salinity affected deep waters, such as the Antarctic Bottom Water (AABW) and the North Atlantic Deep Water (NADW), which are formed in the Southern Ocean and in the northern North Atlantic, respectively. In this study, we present the evolution of the physical properties and distribution of the AABW and the NADW since the last glacial maximum using the results of a transient simulation with NCAR-CCSM3. In this particular model scenario with a schematic freshwater forcing, we find that modern NADW, with its characteristic salinity maximum at depth, was absent in the beginning of the deglaciation, while its intermediate version—Glacial North Atlantic Intermediate Water (GNAIW)—was being formed. GNAIW was a cold and relatively fresh water mass that dominated intermediate depths between 60 and 20°N. At this time, most of the deep and abyssal Atlantic basin was dominated by AABW. Within the onset of the Bolling-Allerod period, at nearly 15 thousand years ago (ka), GNAIW expanded southwards when the simulated Meridional Overturning Circulation overshoots. The transition between GNAIW and NADW ocurred after that, when AABW was fresh enough to allow NADW to sink deeper in the water column. When the NADW appears (~11 ka), AABW retracts and is constrained to lie near the bottom.

스노우팩-융설 계산을 위한 에너지수지 알고리즘

Understanding snowmelt movement to the watershed is crucial for both climate change and hydrological studies because the snowmelt is a significant component of groundwater and surface runoff in temperature area. In this work, a new energy balance budget algorithm has been developed for melting snow from a snowpack at the Central Sierra Snow Laboratory (CSSL) in California, US. Using two sets of experiments, artificial rain-on-snow experiments and observations of diel variations, carried out in the winter of 2002 and 2003, we investigate how to calculate the amount of snowmelt from the snowpack using radiation energy and air temperature. To address the effect of air temperature, we calculate the integrated daily solar radiation energy input, and the integrated discharge of snowmelt under the snowpack and the energy required to generate such an amount of meltwater. The difference between the two is the excess (or deficit) energy input and we compare this energy to the average daily temperature. The resulting empirical relationship is used to calculate the instantaneous snowmelt rate in the model used by Lee et al. (2008a; 2010), in addition to the net-short radiation. If for a given 10 minute interval, the energy obtained by the melt calculation is negative, then no melt is generated. The input energy from the sun is considered to be used to increase the temperature of the snowpack. Positive energy is used for melting snow for the 10-minute interval. Using this energy budget algorithm, we optimize the intrinsic permeability of the snowpack for the two sets of experiments using one-dimensional water percolation model, which are <TEX>$52.5{\times}10^{-10}m^2$</TEX> and <TEX>$75{\times}10^{-10}m^2$</TEX> for the artificial rain-on-snow experiments and observations of diel variation, respectively.

Buffering of sublimation loss of subsurface ice by percolating snowmelt: a theoretical analysis

AbstractSubsurface ice in cold hyperarid conditions retreats by sublimation and diffusion through the overlying soil layer. Here, it is shown that percolating meltwater, if present, can counterbalance sublimation loss effectively and thus increase the persistence time of subsurface ice. Time averaging of transport equations is used to evaluate the significance of percolation in an otherwise complex dynamical system. The reduction in sublimation loss is approximately given by the amount of meltwater multiplied by the percolation depth and divided by the depth to the ice table. It is plausible that percolation is even more effective during a warmer, wetter climate. Copyright © 2009 John Wiley &amp; Sons, Ltd.

An ultrastructural study of the eye of Gomphiocephalus hodgsoni, a collembolan from Antarctica

The collembolan Gomphiocephalus hodgsoni is one of a few hexapods occurring in Antarctica. Male and female individuals do not differ with regard to their eyes. Both possess eight single-lens eyes. In the adults, each lens has a diameter of 10–12 μm and covers an almost spherical crystalline cone made up of four unequal moieties. When we accepted homogenous refractive indices, known from pterygote insect eyes, and then calculated the focal length of the dioptric apparatus, we found that light could be focused on the retina. The retinal cells of each eye are grouped in two tiers and surround the centrally fused rhabdom. Rhabdomeric microvilli, approximately 1.3 μm long, possess a diameter of 80 nm and are typically aligned in one direction. More proximally, however, two rhabdomeres with microvilli perpendicular to the larger, more distal, rhabdom appear. Signs of light-induced damage, despite the bright summer radiation in Antarctica, were not seen. Ricegrain-like screening pigment granules, measuring 0.8×0.45 μm in dimensions, densely surround each rhabdom and shield the cytoplasm of the surrounding cells. The orthogonal arrangement of the microvilli suggests that G. hodgsoni could be sensitive to light-polarization. This ability might be of importance in detecting tiny amounts of meltwater in close proximity to the insect.

Glacial meltwater dynamics in coastal waters west of the Antarctic peninsula.

The annual advance and retreat of sea ice has been considered a major physical determinant of spatial and temporal changes in the structure of the Antarctic coastal marine ecosystem. However, the role of glacial meltwater on the hydrography of the Antarctic Peninsula ecosystem has been largely ignored, and the resulting biological effects have only been considered within a few kilometers from shore. Through several lines of evidence collected in conjunction with the Palmer Station Long-Term Ecological Research Project, we show that the freshening and warming of the coastal surface water over the summer months is influenced not solely by sea ice melt, as suggested by the literature, but largely by the influx of glacial meltwater. Moreover, the seasonal variability in the amount and extent of the glacial meltwater plume plays a critical role in the functioning of the biota by influencing the physical dynamics of the water (e.g., water column stratification, nearshore turbidity). From nearly a decade of observations (1991-1999), the presence of surface meltwater is correlated not only to phytoplankton blooms nearshore, but spatially over 100 km offshore. The amount of meltwater will also have important secondary effects on the ecosystem by influencing the timing of sea ice formation. Because air temperatures are statistically increasing along the Antarctic Peninsula region, the presence of glacial meltwater is likely to become more prevalent in these surface waters and continue to play an ever-increasing role in driving this fragile ecosystem.

The water balance of an arctic lake and its dependence on climate change: Tvillingvatnet in Ny-Ålesund, Svalbard

Lake Tvillingvatnet is the water supply to the arctic research settlement Ny-Ålesund in Svalbard. In the period 1920-1930 it was observed that the lake received groundwater from a sandstone-aquifer underlying the lake. Recent water balance studies indicate that there is no longer any groundwater flow of that type into the lake. This change can be explained by a warmer climate resulting in a fast retreat of the glaciers after the Little Ice Age. Large amounts of melt water combined with a steep hydraulic gradient may have caused partial melting of permafrost along the front of the Brøggerbreen Glacier, which was situated c . 0.5 km west of Lake Tvillingvatnet at that time. Today, the glacier front is more than a kilometre SW of the lake. The formation of new permafrost has resulted in freezing of the previously active groundwater outflow channels. The present flow of water into Tvillingvatnet during the autumn is probably due to shallow groundwater in the active layer along the talus of the Zeppelinfjellet Mountain.

Oxygen and carbon stable isotope tracers of Weddell Sea water masses: new data and some paleoceanographic implications

Stable oxygen isotopic composition of sea water and stable carbon isotopes of dissolved inorganic carbon (DIC) on the continental shelf in the southern Weddell Sea are presented. Using the stations sampled during the summer 1995 two sections can be constructed, one closely parallel to the ice shelf edge and the other perpendicular to the upper continental slope. Generally, δ 18O values clearly separate between different shelf water masses depending on the content of meteoric meltwater added during melting of glacial ice. Extrapolation of the mixing line between the cores of High Salinity Shelf Water (HSSW) and supercooled Ice Shelf Water (ISW) reveals δ 18O values of the glacial ice of −27‰, whereas extrapolation of the mixing line between the δ 18O values of the most-saline HSSW and lowest temperature ISW results in δ 18O values of −34‰ for glacial ice. These values point to an origin of meltwater from below the ice shelf, where ice is less depleted in 18O, since deep beneath the ice shelf close to the grounding line, values may reach −40‰. If values between −34 and −27‰ are used as δ 18O end member values for glacial ice, the amount of meltwater from the ice shelf that adds to the formation of ISW off the Filchner–Ronne Ice Shelf ranges from 0.2 to 0.8%, in agreement with previous studies based on δ 18O and 4He. Carbon isotopic fractionation due to gas exchange between the atmosphere and the ocean at cold temperatures results in Δ δ 13C DIC values of 0.20±0.17‰ for Weddell Sea Deep Water, the water mass that ventilates the global abyssal ocean, typically defined as Antarctic Bottom Water (AABW). This confirms the low end of the range estimated previously (0.2–0.4‰), and thus corroborates the dominance of biology in shaping the deep and bottom water δ 13C signal. It has been hypothesized that different modes of glacial/interglacial Antarctic bottom water formation may be separated by different stable isotopic compositions of deep-sea foraminiferal calcite. Here I show that differences between Δ δ 13C and δ 18O values of HSSW and ISW, both of which contribute to bottom water formation today, are too small to be resolved in deep and bottom water masses. Therefore, glacial/interglacial changes in relative proportions of these water masses in Antarctic deep and bottom water cannot be separated by stable isotopes of fossil benthic foraminiferal calcite.

Lava and ice interaction at stratovolcanoes: Use of characteristic features to determine past glacial extents and future volcanic hazards

Structures resulting from lava and ice interaction are common at glaciated stratovolcanoes. During summit eruptions at stratovolcanoes, meltwater is produced and travels freely down steep slopes and thin permeable valley glaciers, eroding the ice and enlarging preexisting glacial drainages. As a result, eruptions in this environment have produced few catastrophic floods. Lava flowing into the open channels and voids in the glaciers becomes confined and grows thicker, filling the available space and producing steep‐sided bodies with smooth, bulbous contact surfaces. Quenching of lava against ice or by water forms small‐scale features such as tensional fractures and glass. As the amount of meltwater in contact with the lava increases, the type and abundance of smaller‐scale features become similar to those produced during subglacial eruptions into meltwater lakes. Identification of large‐ and small‐scale lava‐ice contact features in the field can be used to reconstruct paleoglacial extent and, combined with geochronology of lavas, to determine past paleoclimate. An understanding of lava‐ice interaction allows us to better assess the hazards posed by future eruptions at glaciated volcanoes.

Radar investigations of melt pathways in a natural snowpack

Melt pathways in a natural seasonal snowpack were investigated using high frequency FMCW radar to examine the use of radar as a tool for investigating water flow through snow, and to develop preliminary estimates of the number of flow fingers present and the amount of meltwater that they transport. Our data show that the radar can be used to sense melt features at distances of approximately one metre within this snowpack. Old refrozen fingers and new wet fingers both generate visible radar returns. Excavation of channels within the snowpack verified that the radar signals were from flow fingering. By counting the number of channels observed in the radar images and using snow lysimeter measurements of outflow from the snowpack, we estimated that in the early stages of the main snow melt season, this snowpack contained approximately three channels/m2, and that the flow through each channel was approximately 0·4 mm of water/channel/hour.

Estimate of ablation rate of glacier ice under a supraglacial debris layer

The ablation rate under a debris layer is very difficult to measure directly at debris‐covered glaciers, because the surface is highly heterogeneous, and the ablation rate varies tremendously from place to place. Heat budget considerations with a debris layer on top of glacier ice suggested that ‘thermal resistance’ of the debris layer could be estimated from surface temperature and the heat fluxes at the debris surface, and the ablation rate of the underlying glacier ice from the thermal resistance and meteorological data. The method was tested at the Lirung Glacier in Langtang Valley, Nepal Himalayas, using the thermal band of LANDSAT satellite for estimating surface temperature distribution of the debris top surface. The amount of melt water thus estimated was compatible with the observed discharge data from the glacier basin for periods of the monsoon season in 1985 and the pre‐monsoon to the monsoon season in 1996. The investigation also revealed that the amount of discharge was much larger than the amount of precipitation over the basin, and it was suggested that the melt water from the debris‐covered glacier contributes significantly to the river flow as a result of the shrinkage of the glacier.

Mass Balance Features Derived from a Firn Core at Hielo Patagónico Norte, South America

Glaciological research was carried out in November and December 1996 in the accumulation area of Glaciar Nef, an eastward-facing glacier from Hielo Patagónico Norte (Northern Patagonia Icefield), South America. A 14.5-m-deep firn core (9.7 m water equivalent: w.e.) was obtained at 1500 m a.s.l., and air temperature and melting rate were also measured. Values of δ18O of 1- or 2-cm-thick samples in the upper 6 m of the firn fluctuated from −16 to −10±, which are explained by variations in δ18O of precipitation. Below 6 m in the firn, δ18O was almost constant, due to percolation of large amounts of meltwater. It was considered that the upper 6 m was deposited during the prior winter; thus winter balance in 1996 was derived as +3.5 m w.e. Based on the measurement results and climatic data, winter and summer ablations were estimated at 0.0 and 3.4 m w.e., respectively, and summer accumulation at 2.1 m w.e. Then, net balance in the calendar year 1996 was estimated at about +2.2 m w.e. Comparison with previous studies and candidate drilling sites are also discussed.

Meltwater Discharge to the Skagerrak–Kattegat from the Baltic Ice Lake during the Younger Dryas Interval

Diatom data from the Skagerrak–Kattegat show that large amounts of meltwater were discharged into the Kattegat–Skagerrak from the Baltic Ice Lake during the Younger Dryas interval. Strong meltwater discharge greatly freshened surface-water salinity in the Kattegat and areas along the Swedish west coast and possibly changed the directions of sea-surface salinity gradients from north–south to east–west or northwest–southeast. It resulted in a markedly stratified water column in salinity in the Kattegat, which complicates the environmental interpretation based on different types of microfossils. The meltwater influence on the large area of the Skagerrak during the Younger Dryas was, however, restricted along the Norwegian coast where it flowed into the Norwegian Sea.