Previous rapid thinning of Pine Island Glacier sheds light on future Antarctic ice loss

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New research, published this week in Science, suggests that the largest single contributor to global sea level rise, a glacier of the West Antarctic Ice Sheet, may continue thinning for decades to come. Geologists from the UK, USA and Germany found that Pine Island Glacier (PIG), which is rapidly accelerating, thinning and retreating, has thinned rapidly before. The team say their findings demonstrate the potential for current ice loss to continue for several decades yet.Their findings reveal that 8000 years ago the glacier thinned as fast as it has in recent decades, providing an important model for its future behaviour. The glacier is currently experiencing significant acceleration, thinning and retreat that is thought to be caused by ‘ocean-driven’ melting; an increase in warm ocean water finding its way under the ice shelf.After two decades of rapid ice loss, concerns are arising over how much more ice will be lost to the ocean in the future. Model projections of the future of PIG contain large uncertainties, leaving questions about the rate, timing and persistence of future sea level rise. Rocks exposed by retreating or thinning glaciers provide evidence of past ice sheet change, which helps scientists to predict possible future change. The geologists used highly sensitive dating techniques, pioneered by one of the team, to track the thinning of PIG through time, and to show that the past thinning lasted for several decades.Lead author Joanne Johnson from the British Antarctic Survey (BAS) said: “Our geological data show us the history of Pine Island Glacier in greater detail than ever before. The fact that it thinned so rapidly in the past demonstrates how sensitive it is to environmental change; small changes can produce dramatic and long-lasting results. Based on what we know, we can expect the rapid ice loss to continue for a long time yet, especially if ocean-driven melting of the ice shelf in front of Pine Island Glacier continues at current rates,”Professor Mike Bentley, a co-leader of the project based at Durham University said: “This paper is part of a wide range of international scientific efforts to understand the behaviour of this important glacier. The results we’re publishing are the product of long days spent sampling rocks from mountains in Antarctica, coupled to some exceptionally precise and time-consuming laboratory analyses. …


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Extreme weather caused by climate change decides distribution of insects, study shows

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As climate change is progressing, the temperature of our planet increases. This is particularly important for the large group of animals that are cold-blooded (ectothermic), including insects. Their body temperature is ultimately determined by the ambient temperature, and the same therefore applies to the speed and efficiency of their vital biological processes.But is it changes in average temperature or frequency of extreme temperature conditions that have the greatest impact on species distribution? This was the questions that a group of Danish and Australian researchers decided to examine in a number of insect species.Johannes Overgaard, Department of Bioscience, Aarhus University, Denmark, Michael R. Kearney and Ary A. Hoffmann, Melbourne University, Australia, recently published the results of these studies in the journal Global Change Biology. The results demonstrate that it is especially the extreme temperature events that define the distribution of both tropical and temperate species. Thus climate change affects ectotermic animals primarily because more periods of extreme weather are expected in the future.Fruit flies were modeledThe researchers examined 10 fruit fly species of the genus Drosophila adapted to tropical and temperate regions of Australia. First they examined the temperatures for which the species can sustain growth and reproduction, and then they found the boundaries of tolerance for hot and cold temperatures.”This is the first time ever where we have been able to compare the effects of extremes and changes in average conditions in a rigorous manner across a group of species,” mentions Ary Hoffmann.Based on this knowledge and knowledge of the present distribution of the 10 species they then examined if distribution was correlated to the temperatures required for growth and reproduction or rather limited by their tolerance to extreme temperature conditions.”The answer was unambiguous: it is the species’ tolerance to very cold or hot days that define their present distribution,” says Johannes Overgaard.It is therefore the extreme weather events, such as heat waves or extremely cold conditions, which costs the insects their life, not an increase in average temperature.Drastic changes in storeWith this information in hand, the researchers could then model how distributions are expected to change if climate change continues for the next 100 years.Most terrestrial animals experience temperature variation on both daily and seasonal time scale, and they are adapted to these conditions. Thus, for a species to maintain its existence under varying temperature conditions there are two simple conditions that must be met. …


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#Alternative-Medicine, #Australia, #Decades, #Events, #Health, #Kilometers, #Melbourne, #Planet, #Result, #Species, #Study, #University