Extreme Cold Climate Research Articles

Phylogenetic structure of regional angiosperm assemblages across latitudinal and climatic gradients in North America

AbstractAimPhylogenetic structure of regional species assemblages is determined by environmental conditions and biogeographical history. Typically, assemblages are thought to become increasingly clustered at higher latitudes, because relatively few clades can tolerate low temperatures. However, numerous other patterns can produce phylogenetic structure. Here, we derive and test four hypotheses for phylogenetic structure of all angiosperms and five major angiosperm clades in North America. These are as follows: (a) angiosperms assemblages at higher latitudes are more phylogenetically clustered; (b) stronger phylogenetic clustering occurs in the drier climates of the west; (c) species are more closely related in the warm, dry southwest than in the cooler, wetter northwest; and (d) latitudinal patterns of phylogenetic structure in central North America are intermediate between those of the east and west.LocationNorth America.Major Taxa StudiedAngiosperms.MethodsWe divided North America into 65 regions across three longitudinal zones. We constructed a phylogeny based on the largest time‐calibrated species‐level mega‐tree of plants available. Two phylogenetic metrics were used to quantify phylogenetic structure of angiosperms as a whole and each major clade in each region and were related to four major climate variables using correlation and regression analyses.ResultsFor all angiosperms, results were consistent with our four predictions, with increasing clustering in drier and colder conditions. In many cases, clustering was more strongly related to precipitation than to temperature. Patterns of phylogenetic structure were inconsistent among major angiosperm clades, although the sister clades malvids and fabids did show remarkably similar patterns of net relatedness index.Main conclusionsThe latitudinal temperature gradient has played an important role in assembling species of the continental pool into regional floras. However, other geographical and biogeographical processes are also influential. Extreme dry climate in the southwest has caused more phylogenetic clustering than extreme cold climate. The observed phylogenetic structure patterns are generally consistent with the tropical niche conservatism, acting along distinct gradients of environmental filtering.

Antifreeze Mechanism Study of Ice Growth Inhibition by Spin Labeled Ice Binding Proteins

Ice binding proteins (IBPs) were found to play critical role for various organisms to survive in extreme cold climates. We carried out the study on spin labeled type 1 IBPs whose sequence is from that of the Pseudopleuronectes americanus (winter flounder). The spin labeled sites involved in our study have undergone a manipulation on different directions along the α-helical structure. Site directed spin labeling technique was used to make the spin labeled peptides. Combination of the EPR spectra at low temperatures and observation of their inhibition to the growth of ice crystals gives us insight into their antifreeze mechanism on both molecular scale and microscopic scale. This poster will focus on presenting the experimental result of ice crystal inhibition, while another poster of my fellow student researchers will focus on the EPR result. Osmometer-microscopy technique was used to observe the ice crystals. The changes in antifreeze activities, kinetics of ice crystals’ growths and shapes of the ice crystals by these spin labeled IBPs compared with the wild type IBP were observed and will be discussed in this poster. Results include observations of IBP binding on both sides of the basal plane and prism faces of ice seed crystals. Significant differences between thermal hysteresis and crystal structured due to the binding of the Spin labeled IBPs were observed which is correlated to the EPR spectra at molecular level. Single cystal growth on the horizontal axis is observed within the hysteresis gap of the spin labeled IBPs while the wild type IBP showed no crystal growth during the hysteresis gap. There were various differences between thermal hysteresis values between the different spin labeled IBPs.

Health and productivity of dairy cattle in high altitude cold desert environment of Leh-Ladakh: A review

The environment is usually attributed as the major climatic factor affecting animal health and production system in all agro-climatic zones. There are various environmental components viz. temperature, radiation, snowfall, wind, precipitation, humidity etc. that impact animal health and productivity. Ladakh is a remote and difficult terrain of India for studying the impact of climate change on livestock production. This area is situated at high altitude, which varies from 10,000 to 12,000 feet from mean sea level (MSL) and temperature range is 35° to -35°C. The atmospheric oxygen pressure is 30% short of MSL. Therefore, this region exhibits hypobaric-hypoxia, extreme cold and dry-arid climate for most of the year, which restrict the growth and productivity of the different livestock populations, including dairy cattle. However, demands are very high for milk and milk products by local people, Indian troops deployed in this region and tourists. Availability of fodder and high altitude stress-induced maladies, mountain sickness (brisket edema), stunted growth, infertility, mastitis pneumonia, etc. severely limits the dairy development, which has increased the gap between supply and demand of dairy products in this region. The impact of climate change on livestock production in Ladakh is a relatively ignored research area. Since the literature on the effect of climate change on dairy cattle productivity in Leh-Ladakh is scarce, therefore, the present article reviewed the available reports and presents authors' own observations on how this climate change impacted on health, production and reproduction of dairy cattle in high altitude cold desert.

A Study of High-Altitude-Associated conditions in soldiers less than 50 years of age admitted in the ICU of a tertiary care military hospital operating in a counter insurgency operation area

Background: Altitude related diseases due to low barometric pressure and extreme cold climates are presumed to be the morbidities for soldiers carrying out military operations at altitudes varying from 2500 to 5500 meters above Mean Sea Level (MSL). Aim: The aim of the study was to ascertain high-altitude-related diseases among soldiers

Testing the ability to enhance nitrogen removal at cold temperatures with C. aquatilis in a horizontal subsurface flow wetland system

The purpose of this study was to determine how well Carex aquatilis would intake nitrogen to remove it from municipal wastewater with decreasing temperatures and light, simulating summer and fall conditions in Baker Lake, Nunavut. Two trials were conducted, one at 0–5°C and another at 5–10°C in a controlled environmental chamber with parallel planted and unplanted planted microcosms. This study specifically examined reduction rates for ammonia, (NH3–N), nitrate (NO3− −N), nitrite (NO2− −N) and Total Kjeldahl Nitrogen (TKN). Wastewater was pumped at a rate of 27L/day and influent and effluent were sampled twice per week for four weeks. Our results showed that the planted trials outperformed the controlled trials at both temperature regimes. In particular, there was a 98% decrease in NH3–N concentration for the 5–10°C and 78% decrease for the 0–5°C trial. We believe direct uptake by the plant is the reason for the removal. The planted system also showed a 92 percent increase in SO42− −S concentration (p<0.01). Further research needs to be completed to determine how effective horizontal subsurface constructed wetlands are when built on shallow soil for extreme cold climate constructed wetlands.

Study on ecological cost-effectiveness for the thermal insulation of building external vertical walls in Poland

Improving the energy efficiency of buildings is not a new issue. It is a challenge not only in Poland but also in many other European countries, which is proved by the actions and initiatives taken by the European Union. Due to the fact that Poland lies in a warm moderate temperate zone, with transition to the impact of marine and continental climate, the issue of thermal insulation of buildings is important in terms of economy and ecology. The paper proposes a method and an analysis of the ecological cost-effectiveness for the investment involving the thermal insulation of external vertical walls for two different buildings in five climate zones located in Poland. The authors based their study on the life cycle assessment (LCA) technique. The analysis took into account different components, such as: heat sources, thermal insulation and construction materials, and usable areas of the analyzed buildings. Popular building materials on the Polish market, and more, were also included. The studies were performed on two single-family houses with a similar usable area, which are representative on the European market. The most favourable values of ecological cost-effectiveness were obtained among the examined options for most ecological thermal insulation material (eco-fibre), the type of heating with the highest environmental impact (electricity) and the most extreme (cold) climate occurring in Poland. The ecological payback period of thermal insulation investment for the studied variants were obtained in the range 0–6 years. The proposed method proved to be very helpful in assessing various options for thermal insulation investments. It can also be used in other places in the world. It allows to take into account both the environmental and economic aspects of the investment. This method could be useful for designers and energy/environmental auditors.

Seasonal changes in gastric mucosal factors associated with peptic ulcer bleeding.

A close association has been established between climate and peptic ulcer bleeding (PUB). The incidence of PUB in cold climates is significantly higher than that in hot climates. In this study, gastric mucosal damage and its barrier function (through associated barrier factors) in extreme climate conditions were examined to investigate the pathogenesis of PUB in extreme cold climates. Gastric juice and biopsy specimens were collected from 176 patients with peptic ulcer. Conventional hematoxylin and eosin staining was used to exclude malignant ulcers. Helicobacter pylori infections were detected by modified Giemsa staining. pH values of the gastric juice samples were obtained on-site by precise pH dipstick readings. The protein expression levels of heat shock protein (HSP) 70, occludin, nitric oxide synthase (NOS), epidermal growth factor (EGF) and EGF receptor (EGFR) in the gastric mucosa were detected by immunohistochemistry. No significant differences were identified between the high and low bleeding risk groups in the rates of H. pylori infection and the pH values of the gastric juices in the extreme hot or cold climates. Furthermore, no statistically significant differences were identified in the protein expression levels of occludin, NOS, EGF and EGFR between the high and low bleeding risk groups. In the extreme cold climate, the expression of HSP70 and the mucus thickness of the gastric antrum in the high bleeding risk group were significantly lower than those in the low bleeding risk group. The protein expression levels of occludin, HSP70, NOS and EGFR in the extreme cold climate were significantly lower than those in the extreme hot climate, whereas the gastric acid secretion was significantly higher in the extreme cold climate than that in the extreme hot climate. In conclusion, low expression of HSP70 in the gastric mucosa and reduced gastric mucus thickness may play key roles in the mechanism of PUB in extreme cold climates. The significant decrease in barrier factors and increase in damage in extreme cold climates may be associated with the seasonal pattern of peptic ulcers.

Building application and thermal performance of vacuum insulation panels (VIPs) in Canadian subarctic climate

Vacuum insulation panels (VIPs) have thermal resistance values, at the center of the panel, up to 10 times or more than those of conventional thermal insulation materials. In Canada, known for its predominantly extreme cold climate, the potential to apply VIPs in the building construction industry is estimated to be enormous, particularly with the introduction of the new 2011 National Energy Code of Canada for Buildings (NECB 2011). VIPs can play a major role in Canadian buildings to meet energy requirements of the NECB 2011. However, the lack of long-term performance credentials and various constructability issues are among the major barriers for mass application of VIPs in the Canadian construction industry. This paper presents the design strategy, construction details, instrumentation and thermal performance monitoring observations of a VIP retrofitted wall system in Yukon, located in Northern Canada. Experience gained from the construction process and available thermal performance data over a period of three years provide encouraging indicators for the constructability and long-term thermal performance of VIPs in Canadian subarctic weather.

Genome-wide analysis of cold adaptation in indigenous Siberian populations.

Following the dispersal out of Africa, where hominins evolved in warm environments for millions of years, our species has colonised different climate zones of the world, including high latitudes and cold environments. The extent to which human habitation in (sub-)Arctic regions has been enabled by cultural buffering, short-term acclimatization and genetic adaptations is not clearly understood. Present day indigenous populations of Siberia show a number of phenotypic features, such as increased basal metabolic rate, low serum lipid levels and increased blood pressure that have been attributed to adaptation to the extreme cold climate. In this study we introduce a dataset of 200 individuals from ten indigenous Siberian populations that were genotyped for 730,525 SNPs across the genome to identify genes and non-coding regions that have undergone unusually rapid allele frequency and long-range haplotype homozygosity change in the recent past. At least three distinct population clusters could be identified among the Siberians, each of which showed a number of unique signals of selection. A region on chromosome 11 (chr11:66–69 Mb) contained the largest amount of clustering of significant signals and also the strongest signals in all the different selection tests performed. We present a list of candidate cold adaption genes that showed significant signals of positive selection with our strongest signals associated with genes involved in energy regulation and metabolism (CPT1A, LRP5, THADA) and vascular smooth muscle contraction (PRKG1). By employing a new method that paints phased chromosome chunks by their ancestry we distinguish local Siberian-specific long-range haplotype signals from those introduced by admixture.

The Research on the Influence Law on Thermal Resistance of Borehole

GSHP are of strategic and necessary part for the efficient utilization of renewable energy and energy conservation. Vertical ground heat exchanger system is one form of GSHP and it is a way to solve the problem of the imbalance between cooling load and heating load except for some extreme hot or cold climate areas. In the paper, the study of underground heat exchanger heat transfer mode, and the influence law of the borehole diameter, shank spacing, and grout conductivities on thermal resistance of borehole are discussed systematically.

Marine Construction and Operation Challenges in the Barents Sea

The Western and Southern Western Barents Sea is the offshore area south of Bear Island and east towards the newly agreed delineation boundary between Norway and Russia, limited by the Norwegian mainland to the south. In this area, the Snøhvit gas field is in production and the Goliat oil field is being developed. Recently, encouraging oil finds (Skrugard and Havsul) have increased the interests in the geology and the oil and gas potential of the area. This paper summarises challenges faced by the marine construction contractors working in these areas and also discusses various phenomena that affect marine operations at extreme cold climate conditions. It is considered important to present a review of all aspects of working in these cold climate areas as construction and operation activities in the areas for a large part will be carried out by personnel unfamiliar with the challenges of the areas. Working under unfamiliar conditions could lead to undesirable events that could escalate into severe accidents.

Endolithic microbial life in extreme cold climate: snow is required, but perhaps less is more.

Cyanobacteria and lichens living under sandstone surfaces in the McMurdo Dry Valleys require snow for moisture. Snow accumulated beyond a thin layer, however, is counterproductive, interfering with rock insolation, snow melting, and photosynthetic access to light. With this in mind, the facts that rock slope and direction control colonization, and that climate change results in regional extinctions, can be explained. Vertical cliffs, which lack snow cover and are perpetually dry, are devoid of organisms. Boulder tops and edges can trap snow, but gravity and wind prevent excessive buildup. There, the organisms flourish. In places where snow-thinning cannot occur and snow drifts collect, rocks may contain living or dead communities. In light of these observations, the possibility of finding extraterrestrial endolithic communities on Mars cannot be eliminated.

Experimental investigation of the reliability of residential standing column heat pump systems without bleed in cold climates

Typical houses located in Eastern Canada generally require a 160 m deep vertical closed-loop heat exchanger for efficient ground-source heat pump systems. Borehole drilling costs for such ground heat exchangers are still relatively high. One of the concepts that could potentially reduce these costs is the standing column system, with or without groundwater bleeding. Such a system has been successfully validated in moderate climates for relatively short periods of operation in the heating mode. The scope of this article is to determine the reliability of residential standing column heat pumps without bleed operating in extreme cold climate conditions, i.e. running in the heating mode continuously or intermittently over indefinite periods of time. The analyses and tests indicate that standing column wells are not appropriate for use with ground-source heat pumps in extreme cold climates unless some groundwater bleed is employed.

Descriptive Anatomy of the Pelvic Appendage Myology of the Endemic Chinese Grouse (Tetrastes sewerzowi)

The musculature of the pelvic appendage of the Chinese Grouse (Tetrastes sewerzowi) is described in detail. T. sewerzowi exhibits the same features as other tetraonids in the absence of M. adductor digiti II, and the relatively weak development of other intrinsic foot muscles, which are thought to be an adaptation to the extreme cold climate of the habitat of grouse. Myological modifications include weak development of the vincula between the flexor tendons to the digits (M. flexor perforans digiti III and M. flexor perforans et perforatus digiti III, M. flexor digitorum longus, and M. flexor hallus longus), the proximolateral insertion of M. flexor perforans digiti II, the well-developed middle head of M. flexor perforans digiti IV, and the ossification of the insertion tendon of M. extensor brevis digiti IV. These features are suggested to be associated with the requirement of finer control over the individual digits while moving on the tree, especially a thin branch.

Human Settlements in High Altitude Region Nepal

Nepal has human settlements in high altitude areas above 3 000 masl. Those areas of Himalayan region have extreme cold climate, rugged terrains, fragile geology and slow growing vegetation, which all create very low carrying capacity for human life. Despite these, the ethnic groups have been living in those areas for several hundred years. Yet, information on those settlements in Nepal is extremely lacking and therefore, our knowledge of understanding of planning and development needs of those areas is very poor. This paper is an attempt to identify the human settlements lying above 3 000 m and analyse their distribution and size. Topographic maps of 1:50 000 have been used to find out location and size of those settlements. GIS and other software were used to extract and process required information. There are 1,282 high altitude settlements in Nepal with estimated households and population of 9,827 and 51,486 respectively. This paper analyses those settlements by altitudinal zones, major river basins from west to east, and size. The results would be helpful for further planning and development of those settlements with respect to the locally available natural resources.The Geographical Journal of Nepal, Vol. 7, 2009: 1-6

Twenty-five years of change in scleractinian coral communities of Daya Bay (northern South China Sea) and its response to the 2008 AD extreme cold climate event

Coral reefs worldwide are becoming increasingly and detrimentally impacted upon by a variety of factors including significant climate changes, such as global warming and increased El Nino-Southern Oscillation activity. Generally, the persistence of coral reefs, especially at low-latitudes, is governed, in part, by sea surface temperatures not exceeding the critical limit (similar to 30A degrees C) at which mass mortality can occur. Thus, it is thought that corals living at high-latitudes (i.e., currently cooler sea surface temperatures) will likely respond more favourably to hypothesized future temperature increases than corals living at low-latitudes (i.e., currently warmer sea surface temperatures). Consequently, high-latitude coral communities may have the potential to act as regions of refugia for many coral species in the face of potential future global warming. The Daya Bay (22A degrees 31'aEuro22A degrees 50'N), northern South China Sea, contains several high-latitude non-reefal coral communities and represents one of the most northerly distributions of scleractinian corals within the region. Significantly, Daya Bay has experienced dramatic warming in both air and sea surface temperatures throughout the past 50 years. In this paper, we analyze 25 years of change in the Daya Bay coral communities, based both on historic surveys and our latest 2006-2008 regional ecological surveys. Our results suggest that, contrary to predictions, there have been significant declines in coral cover within the Daya Bay during the past 25 years (i.e., 76.6% coral cover in 1983/1984 to only 15.3% coral cover by 2008). Such changes also reflect a significant shift in the most abundant coral species, from Acropora pruinosa to Favites abdita. Most of the modern coral communities became established between 15 and 30 years ago, corresponding to a period of increased winter sea surface temperature. However, very few colonies have become established within the last 15 years, despite a more intense period of warming. By taking into account additional factors, we hypothesize that direct anthropogenic impacts, rather than climatic events, have both restricted the development, and drove the decline, of Daya Bay coral communities in the last 15 years. The Daya Bay has also been subjected to occasional extreme cold events during the past 50 years, with the most recent occurring in early 2008 (13 January-13 February). During the 2008 cold event, the lowest air temperature reaches only 6.6A degrees C, and the mean sea surface temperature for February fall to < 14A degrees C, including six continuous days at 12.3A degrees C. Significantly, the sea surface temperatures fall below the hypothesized critical lower temperature threshold (similar to 13A degrees C) that commonly leads to mass mortality in scleractinian coral communities. Surprisingly, our coral community surveys, conducted both before (August 2007) and after (late February 2008) the extreme 2008 cold event, demonstrate that the Daya Bay coral ecosystems are barely impacted upon during the cold period. Those observations suggest that the Daya Bay scleractinian coral communities have developed adaptations to low sea surface temperatures. Overall, our data support the hypothesis that high-latitude coral communities, such as Daya Bay, have the potential to act as areas of refugia for scleractinian corals in the advent of potential future global warming.

Spore-pollen-climate factor transfer function and paleoenvironment reconstruction in Dajiuhu, Shennongjia, Central China

The identified results of 121 surface sediment spore-pollen samples in Shennongjia and meteorological data base of 30 years (January, 1971–December, 2000) of 7 meteorological stations around Dajiuhu, Shennongjia are used in this study. Selecting 55 species of common spore-pollen with the method of space fitting and stepwise regression we construct the pollen climate factor transfer function of annual mean temperature: T = 7.649 − 2.33097X Abies − 0.10873X Betula − 0.17352X Compositae − 0.13176X Cruciferae + 0.13356X Euphorbiaceae − 0.83069X Campanulaceae + 1.96494X Pyrrosia + 0.38411X Pteris + 2.77741X Selaginella + 0.04439X Monolites . We had reconstructed annual mean temperature series by use of the sporo-pollen samples concentra-tion percentage in peat section with 297 cm thickness in Dajiuhu since 15.753 kaBP. The temperature series reflect well the character of climatic change since the late glacial, which indicates extreme cold climate event of the Oldest Dryas, the Older Dryas, the Younger Dryas and the 8.2 kaBP, the same to the climate fluctuations of Bolling Warm Period and Allerod Warm Period, and the character of temperature change fluctuating frequently at the transition age from the late glacial to the Holocene. The reconstructed temperature also indicate Holocene Optimum, late Holocene warm-dry climate, and the character of climatic change in Dajiuhu in the last 1 ka. The conclusion is that the sporo-pollen samples have important climatic significance to surface sediment and the section of Dajiuhu, Shennongjia and important reference value to studying climatic change during the last glaciation by the temperature transfer function and reconstructed temperature series.

Co‐occurrence based assessment of habitat generalists and specialists: a new approach for the measurement of niche width

Summary Much ecological theory is based on the characterization of ecological habits of species as ‘generalist’ or ‘specialist’, but standard measures for placing species along a generalist‐specialist gradient do not exist. We introduce a method for quantifying habitat specialization (i.e. relative niche widths) using species co‐occurrence data. Generalists should co‐occur with many species, whereas specialists should co‐occur with relatively few species, given equal plot occurrences. We quantify this concept using a generalist‐specialist metric (θ) derived from a beta diversity statistic. We evaluate the ability of our generalist‐specialist metric to correctly rank species according to simulated (known) niche widths. Our technique is generally robust to a wide variety of niche distribution structures and sampling designs, but surveys strongly biased toward certain habitats can undermine the ability of θ to accurately describe niche widths for underrepresented species. We apply our technique to three spatially nested surveys of the large woody flora (&gt; 1 cm d.b.h.) of the south‐eastern USA. For each dataset we rank the generalist‐specialist tendencies of all species of non‐trivial occurrences, including 113 species across the Southeast, 71 species of southern Appalachian forests, and 44 species of the 6800‐ha Joyce Kilmer‐Slickrock Wilderness Area (NC and TN, USA). Rankings of species’θ‐values were generally consistent among datasets of different spatial extent. Generalist species (e.g. Ilex opaca, Ulmus rubra, Morus rubra, Prunus serotina, Acer rubrum) were often those with large geographical ranges, particularly for θ‐values from the largest dataset, and overall were more likely to be bird‐dispersed, deciduous, and shade tolerant. South‐eastern specialist species (e.g. Taxodium spp., Abies fraseri, Quercus laevis, Pinus pungens, Pinus palustris) were those associated with stressful or unusual conditions, such as a long duration of flooding, high fire frequency, or extreme cold or dry climates. Our study demonstrates that increasingly available, large‐survey datasets can contribute niche‐related species information in the absence of detailed environmental or habitat measurements. Applications include new assessments of relationships between species traits, ecological and environmental tolerances, and species packing in different assemblages.

Climatic warming: a trigger for glacial iceberg surges (‘Heinrich events’) in the North Atlantic?

In the present-day western North Atlantic, icebergs can be observed off north-east Canada, drifting south along the coast in the cold Labrador Current. Normally they melt in the area off Newfoundland where they reach warmer waters. Most of these icebergs originate from calving glaciers in West Greenland or in the Canadian Arctic. Jakobshavn Isbræ in West Greenland (Fig. 1) deserves particular mention as it is the fastest known ice stream in the world draining 6–7% of the entire Greenland ice sheet (Joughin et al. 2004). Southward drifting icebergs also occur along the east coast of Greenland (Fig. 2), but most of these melt when they approach the southernmost tip of Greenland. The iceberg limit in the north-western Atlantic varies from year to year, but isolated icebergs may reach far south of Newfoundland (Fig. 1). Many icebergs carry a load of rock debris and soil incorporated by their parent glacier that leads to deposition of ice rafted debris on the deep ocean sea floor. In the past decade the Geological Survey of Denmark and Greenland (GEUS) has initiated marine geological investigations in the North Atlantic on the late Quaternary variability of North Atlantic thermohaline circulation, with special focus on the possible link between climate change and variations in deep-water flow intensity (Kuijpers et al. 1998, 2002, 2003). Moreover, glaciological projects in Greenland undertaken by GEUS have significantly contributed to the current debate of present-day climatic warming. Notably work carried out in East Greenland fjords has provided crucial information relevant for the study of glacial iceberg surges in the North Atlantic (Reeh et al. 1999). These surges are suggested to have been triggered under the influence of extreme cold climate conditions, but the actual trigger mechanism involved has been a matter of much debate. Evidence from modern glacier process studies referred to above, combined with results of recent studies in the North Atlantic carried out by GEUS and partner institutions, has provided new insights into the possible trigger mechanism of these massive glacial iceberg surges. These new findings have great significance for the current climate debate, since they strongly suggest that ongoing ocean warming can trigger a sudden, massive break-up of ice shelves. Such processes may already be in progress in the Arctic (e.g. Vincent et al. 2004), where rapid ice-shelf disruption on the margin of the Canadian Arctic Ocean has been reported to be the result of significant warming over the past few decades. During this period intensified inflow of Atlantic water to the Eurasian sector of the Arctic has been noted. It is evident that for Antarctic ice shelves large-scale disruption and break-up may lead to significant destabilisation of the Antarctic ice sheet with the serious risk of a sudden, drastic sea-level rise.

Monsoon related changes in sea surface productivity and water column denitrification in the Eastern Arabian Sea during the last glacial cycle

Sea surface salinity reconstruction for the Holocene and the Last Glacial Maximum (LGM) suggests that the LGM-Eastern Arabian Sea was more saline (by ∼ 1.5 psu) than the Holocene due to weakened freshwater flux to the region, and intensified winter monsoons. Time-series of sedimentary organic-carbon (C org), ∑alkenone and δ 13C org for the last 100 kyr, together, indicate increased glacial productivity. Significantly reduced sedimentary-δ 15N during the LGM indicates, however, diminished water column denitrification in spite of increased productivity. The distinct decoupling of denitrification from productivity during the LGM can be explained by vigorous ventilation of the thermocline as a result of simultaneously intensified formation of high-salinity water and deep-winter mixing in northern-Arabian Sea related to the extreme cold climate. The closely comparable time-series δ 15N records across the Arabian Sea suggest basin-wide homogenisation of the isotopic signal. This probably resulted from combined monsoon-dependent surface water mixing, due to changes in the relative strength of reversing surface circulations, and intermediate water mixing, due to changes in north–south salinity gradient.