News Article | November 16, 2016
Environmental DNA in seawater samples may provide accurate information about deepwater fish populations, according to a study published November 16, 2016 in the open-access journal PLOS ONE by Philip Francis Thomsen from the Centre for GeoGenetics at the Danish Natural History Museum, University of Copenhagen, Denmark, and colleagues. Fish in remote polar and deepwater habitats are threatened by climate change and increased fishing efforts, making it important to monitor populations. However, monitoring can be logistically difficult and currently depends on invasive techniques such as bottom trawling and unreliable reports of catches. Less invasive, more reliable monitoring techniques are therefore needed. To address this need, Thomsen and colleagues assessed an alternative monitoring technique which relies on sequencing environmental DNA (eDNA) in seawater samples. They collected seawater samples at sites off Southwest Greenland, at varying depths between 188 and 918 meters, sequencing the DNA in these samples to determine the fish species present. They compared these results to catch data obtained by simultaneous trawling at each site. Thomsen and colleagues found that data on fish biomass and abundance was correlated with eDNA sequence abundance. Twenty-six families of fish, including rays and halibut, were identified by both trawling and environmental DNA techniques, compared to just two families found only in trawling and three found only in eDNA. Environmental DNA sampling also detected a higher abundance of the Greenland Shark than trawling did, which may indicate that the technique can effectively detect large fish which may evade trawling nets. Environmental DNA sampling will need to undergo further testing to determine its effectiveness as a monitoring technique. Nonetheless, the authors state their study demonstrates how eDNA could be used in non-invasive monitoring, for commercial fishing as well as to assess the impact of climate change on the biodiversity of these remote ecosystems. In your coverage please use this URL to provide access to the freely available paper: http://dx. Citation: Thomsen PF, Møller PR, Sigsgaard EE, Knudsen SW, Jørgensen OA, Willerslev E (2016) Environmental DNA from Seawater Samples Correlate with Trawl Catches of Subarctic, Deepwater Fishes. PLoS ONE 11(11): e0165252. doi:10.1371/journal.pone.0165252 Funding: Danish National Research Foundation funded the work. Greenland Institute of Natural Resources, Greenland Self-government, Department for education and research funded the work. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist.
Merkel F.R.,Greenland Institute of Natural Resources |
Johansen K.L.,University of Aarhus
Marine Pollution Bulletin | Year: 2011
Light-induced bird strikes are known to occur when vessels navigate during darkness in icy waters using powerful searchlight. In Southwest Greenland, which is important internationally for wintering seabirds, we collected reports of incidents of bird strikes over 2-3 winters (2006-2009) from navy vessels, cargo vessels and trawlers (total n=19). Forty-one incidents were reported: mainly close to land (<4 km, 78%), but one as far offshore as 205 km. Up to 88 birds were reported killed in a single incident. All occurred between 5 p.m. and 6 a.m. and significantly more birds were involved when visibility was poor (snow) rather than moderate or good. Among five seabird species reported, the common eider (Somateria mollissima) accounted for 95% of the bird casualties. Based on spatial analyses of data on vessel traffic intensity and common eider density we are able to predict areas with high risk of bird strikes in Southwest Greenland. © 2011 Elsevier Ltd.
News Article | April 20, 2016
The houses of Narsaq gleam in a cheerful riot of blues, reds and yellows. The crayon-coloured town spills across a hill that separates barren mountains from a fjord filled with icebergs. But up close, grimmer details come into focus; the paint on many homes is peeling, and few signs of life stir in the narrow streets. Established as a trading post in 1830, Narsaq long served as a hub of Greenland's fishing industry — the backbone of its economy. But in the past few decades, modernization has moved much of the fishing offshore, and many jobs in Narsaq have disappeared. The town's 1,500 residents have been struggling to find a way forward. The same could be said of Greenland at large. Part of the kingdom of Denmark since 1814, Greenland has transformed over the past century from a society based on subsistence hunting and fishing to one built around an industrial economy and a Nordic-style welfare system. But that rapid development has stalled, leaving communities such as Narsaq to grapple with economic stagnation and high rates of unemployment. At the same time, Greenland has sought to overcome its economic and political dependence on Denmark. “I don't know any people — any country — who don't want self-determination, who don't want independence in the world,” says Hjalmar Dahl, president of the Greenlandic branch of the Inuit Circumpolar Council. Some 80% of Greenland's population is Inuit. Over the past 35 years, Greenland has gained increasing control over its internal affairs — it was granted self rule in 2009 — but it continues to receive Danish subsidies that account for roughly one-third of its gross domestic product (GDP). To gain true independence, it will have to generate almost US$1 billion in additional revenues — all from a population of just 56,000 people on an island with only 150 kilometres of roads and an ice sheet about 3 times the size of Texas. But Greenlandic leaders see promise in places like Narsaq. Geological studies of the rugged peaks outside town have identified valuable deposits of rare-earth metals, uranium and zinc; a major mine is approaching the final stages of obtaining a permit. These are just some of many such deposits that have attracted the attention of international mining companies, and which proponents say could usher in a new era of prosperity. Researchers and some residents have challenged the idea that Greenland can mine its way to independence. A bitter debate has erupted over the social and environmental impacts that mining will have on one of the last pristine parts of the planet. Now, leaders are looking for opportunities — and investors — to expand other industries such as tourism and agriculture, as well as ways to optimize Greenland's vast fishing sector. The government must juggle these goals while contending with climate change, which threatens traditional ways of life and potentially bolsters new ones. Whatever route Greenland chooses to follow, researchers say that it needs to start paving the way now. Even if the island forgoes full political independence, Danish subsidies will remain fixed at 2009 levels, adjusted for inflation, and the funds will not help to cover the rising costs of Greenland's ageing population or to sustain small towns like Narsaq. “It is a very urgent problem because Greenland already runs at a deficit,” says Minik Rosing, a geologist at the University of Copenhagen who is well known in Greenland for his work on the island's future. Unless something changes, he says, “everything points toward the situation getting worse rather than better”. Narsaq's name means 'plain' in Kalaallisut, the official language of Greenland, probably because the town occupies the flattest piece of land in sight. Mountains rise on all sides, their summits dulled by millions of years of glacial erosion. The inland ice sheet lurks just over the horizon, leaving only a thin ribbon of ice-free terrain. But what little exposed land there is happens to be rich in minerals (see 'Mineral futures'). The crust here is ancient — up to 3.8 billion years old, in places — and has seen many cycles of volcanism and rifting. These brought metal-rich fluids close to the surface, where they formed deposits. The island also has substantial offshore oil and gas resources that could come into play if fuel prices rise or exploration costs drop. Interest in the minerals has grown over the past decade, thanks to a confluence of forces. Greenland gained the right to manage and profit from its mineral deposits in 2009, just as the global appetite for many metals started rising. Politicians quickly pointed to mining as the best, and perhaps only, way to offset Danish subsidies and make statehood possible. At the moment, many have their eye on the Kvanefjeld deposit near Narsaq, a contender to host Greenland's first major mine. The resource there is “potentially huge”, says Kathryn Goodenough, a geologist with the British Geological Survey in Edinburgh. She works with EURARE, an initiative to develop Europe's rare-earth potential that brings together researchers and mining companies such as Greenland Minerals and Energy (GME), the Australian company behind the Kvanefjeld project. GME has been exploring here since 2007 and has studied core samples from hundreds of holes drilled into the nearby mountains over the years. “It's like Swiss cheese up there,” says Ib Laursen, a company representative based in Narsaq. GME has estimated that the rocks above the town hold approximately 11 million tonnes of rare-earth oxides and that Kvanefjeld is one of the largest rare-earth deposits outside China. Another company is seeking to develop the Kringlerne deposit across the fjord, which it calls a world-class reserve of rare earths and other metals. Until mining starts, it is not clear whether these deposits will prove as extraordinary as the companies contend, says Rosing. But the geologist, who grew up on a reindeer farm outside the Greenlandic capital, Nuuk, is optimistic about the future of the island's mining industry. “Greenland is exceptional, it is large,” he says. “I think with enough effort, there will be definitely something happening.” Like many Narsaq residents, Mariane Paviasen desperately hopes that the mining boom doesn't start at Kvanefjeld. She works for Air Greenland, greeting the handful of helicopter flights that touch down on Narsaq's blustery landing pad. Her house, at the top of a narrow road on the far side of the town, is bright and inviting on a sunny day in September. Some oppose the mine because it would bring an influx of foreign workers, but Paviasen is most worried about the uranium in the deposit, which GME plans to extract and sell along with the rare-earth elements. It's what first brought Narsaq to the attention of scientists, including Niels Bohr, who visited in 1957 as part of Denmark's investigations into atomic energy. The country later banned all nuclear activity, including uranium mining, and Paviasen wishes that Greenland had upheld the tradition. “I think it is very dangerous stuff — the most dangerous stuff in the world,” she says. That's why, in late 2014, she helped to found a citizens' group called Urani Naamik, or No to Uranium. GME's current plans call for an open-pit mine on top of the plateau, about 10 kilometres from town. Paviasen's group has highlighted the potential risks from uranium to human and environmental health, through water pollution and dust exposure. “My husband and my sons and my father — they like to go out and catch some food,” Paviasen says. But she wouldn't eat it if mining began. Others, including environmental organizations in Denmark, have cited the dangers of the radioactive thorium in the deposits, which currently has little commercial value, and of fluorine-containing minerals that can acidify water. Such concerns have fuelled a heated dispute over how to balance the economic benefits of exploiting Greenland's natural resources with the environmental risks. GME insists that Kvanefjeld can be mined safely. The company says that it is considering ways to contain the thorium, and that it will lock up fluorine by converting it into a marketable mineral. “That's a part of the demand from the government — to use best practices,” Laursen says. Studies have found1 that modern techniques for managing tailings can minimize the contamination risk, at least in the short term. The technical details of GME's plans, however, won't be revealed until the Environmental Impact Assessment report comes out later this year. Economic forces may be the biggest barrier to Greenland's mineral plans: the prices of rare earths and other metals have slumped after reaching all-time highs in 2011. “The simple reality is, it doesn't look good,” says Tim Boersma, a fellow at the Brookings Institution in Washington DC, who co-authored a 2014 report2 on Greenland's mining potential. Greenland would need about 24 major mines operating simultaneously to replace the Danish subsidy, according to a 2014 joint report3 by the University of Copenhagen and the University of Greenland in Nuuk that assessed how the island's mineral resources might shape its future. Given what is known about the deposits, that would be a tall order even in good economic times, says Rosing, who chaired the committee that wrote the report. “The dream that mining could be a quick fix for the economy — that's not going to happen,” he says. As the results of the report have sunk in, talk of political independence has dwindled. Many Greenlanders realize that the process will take time, and Rosing says that some young people have started to question the benefits of completely severing ties with Denmark. In their view, he says, “a nation of 56,000 people is maybe not the best way of ensuring that individuals in Greenland can shape their own future”. Disappointments in the mining sector have spurred discussion about diversifying the strategy for economic self-sufficiency. Rosing suggests that Greenland should devise other ways to profit from what makes it unique. He is exploring the possibility of marketing rock flour — the fine powder created by glacial erosion — as a source of nutrients and neutralizing agents for tropical soils. And he says that Greenland should court industries that would benefit from its cold climate, such as computer-server farms, which use enormous amounts of energy for cooling. Greenland has begun harnessing its torrents of glacial melt water to produce renewable energy. The island has 5 hydropower plants, and government estimates suggest that it has enough untapped potential to produce 800,000 gigawatt hours of energy per year — more than the total used by the United Kingdom and France combined. The aluminium producer Alcoa, based in New York City, has considered building a smelter to capitalize on the cheap energy and, in 2010, Greenland's national energy company launched a pilot project using hydropower to produce clean-burning hydrogen fuel. For the moment, however, those options are largely prospects for the future. Today, about 40% of Greenland's workers are employed by the public sector and 90% of its export economy revolves around fishing, particularly for northern shrimp (Pandalus borealis) and Greenland halibut (Reinhardtius hippoglossoides). Although catches remain good, west Greenland's shrimp stocks have declined over the past decade, perhaps influenced by climate change. According to Helle Siegstad, director of fish and shellfish at the Greenland Institute of Natural Resources in Nuuk, the culprit could be Atlantic cod (Gadus morhua), a predator that could benefit from warming near Greenland and has started to reappear after being overfished. Another factor behind the shrimp's decline might be that climate change has caused a mismatch between their hatching time and the blooms of phytoplankton that they eat4. But higher water temperatures have also lured new species north, such as Atlantic mackerel, Atlantic herring and even some bluefin tuna5, says Brian MacKenzie, a marine ecologist at the Technical University of Denmark in Kongens Lyngby. In recent years, temperatures off the coast of east Greenland have become warm enough for tuna, MacKenzie says. “It's basically a whole new habitat.” Siegstad says that the fishing fleet has been quick to pounce on these opportunities, and she is optimistic that changes in marine ecosystems will ultimately benefit Greenland's fishing industry. But even so, she worries about the island's overwhelming dependence on this variable, uncontrollable resource. “We are so sensitive,” she says. “I hope we will have something else.” Thirty minutes by boat from Narsaq, Kalista Poulsen and Agathe Devisme share 10 hectares of land with 300 head of sheep. Compared with the surrounding tundra, their grassy farm is lush. Purple wildflowers and Angelica archangelica — a popular medicinal herb — line their carefully manicured fields. The couple is part of Greenland's budding agricultural industry — one of several small sectors of the economy that the island's leaders are trying to expand. Agriculture currently accounts for less than 1% of Greenland's GDP, but that figure could grow thanks to climate change, which has boosted temperatures in the south by almost 2 °C over the past few decades. Modelling work6 by Jens Christensen and others at the Danish Meteorological Institute in Copenhagen suggests that if the world warms according to some of the most dramatic projections, the length of the growing season in southern Greenland will more than double. But the climate is likely to become more variable, too. Already, a string of dry summers has forced farmers to import extra supplies of hay from abroad, supplementing the feed that they grow to get the animals through the long, brutal winter. This has left them wondering whether climate change will help or hurt them, says Devisme. “For the moment, it's more, kind of, disturbing.” To supplement their farming income, Devisme also runs a small bed and breakfast, where visitors come to relax or to fish for Arctic char in the stream behind the fields. Many Greenlanders see the island's nascent tourism industry as a welcome alternative to exploitative activities such as the mining at Kvanefjeld, which Devisme says poses a threat to her businesses. In 2013, the government counted roughly 35,000 visitors, who contributed around 3% of GDP. Greenland hopes to ramp up adventure tourism, such as hiking and kayaking, and boost cruise-ship traffic — a pattern that has succeeded in Iceland. The consulting firm Ramboll, based in Orestad, Denmark, has projected that the tourism industry could more than double by 2025, although this would require strong investment in infrastructure such as hotels and airports, as well as increased marketing and international cooperation. But, if Greenland is to benefit from these industries, its people must have the skills to work in them. Developing the island's human capital may be the key to Greenland's success, according to a 2013 report7 by the Copenhagen Institute for Futures Studies. Today, although many Greenlanders possess a wealth of informal knowledge, only 35% of students go beyond compulsory school, which they finish at age 15 or 16. The government aims to boost the number continuing with their training, and the plan starts with strengthening elementary education. The residents of Narsaq are doing their part. Here, late on a Sunday afternoon, workers bustle around a fenced-off construction site in the centre of town. A crane swings overhead, hoisting wooden beams onto a tower of scaffolding, where crews are renovating the red-panelled school. It will soon boast a wall of windows, giving Narsaq's children a grand view of the mineral-rich mountains, the ice-choked fjord and their own small town — as it lurches forward into Greenland's uncertain future.
Stenhouse I.J.,BioDiversity Research Institute |
Egevang C.,Greenland Institute of Natural Resources |
Phillips R.A.,Natural Environment Research Council
Ibis | Year: 2012
The migrations and winter distributions of most seabirds, particularly small pelagic species, remain poorly understood despite their potential as indicators of marine ecosystem health. Here we report the use of miniature archival light loggers (geolocators) to track the annual migration of Sabine's Gull Larus sabini, a small (c. 200g) Arctic-breeding larid. We describe their migratory routes and identify previously unknown staging sites in the Atlantic Ocean, as well as their main Atlantic wintering area in the southern hemisphere. Sabine's Gulls breeding in northeast Greenland displayed an average annual migration of almost 32000km (n=6), with the longest return journey spanning close to 39000km (not including local movements at staging sites or within the wintering area). On their southern migration, they spent an average of 45days in the Bay of Biscay and Iberian Sea, off the coasts of France, Spain and Portugal. They all wintered in close association with the cold waters of the Benguela Upwelling, spending an average of 152days in that area. On their return north, Sabine's Gulls staged off the west African coast (Morocco, Mauritania, Senegal), spending on average 19days at this site. This leg of migration was particularly rapid, birds travelling an average of 813km/day, assisted by the prevailing winds. Sabine's Gulls generally followed a similar path on their outbound and return migrations, and did not exhibit the broad figure-of-eight pattern (anti clockwise in the southern hemisphere and clockwise in the northern hemisphere) seen in other trans-equatorial seabirds in the Atlantic and Pacific oceans. © 2011 The Authors. Ibis © 2011 British Ornithologists' Union.
Laidre K.L.,University of Washington |
Heide-Jorgensen M.P.,Greenland Institute of Natural Resources
ICES Journal of Marine Science | Year: 2012
Movements of co-occurring bowhead (Balaena mysticetus) and humpback (Megaptera novaeangliae) whales in Disko Bay, West Greenland, were examined using satellite telemetry. Data on movements, habitat use, and phenology were collected from tagged 49 bowheads and 44 humpbacks during the transition from sea-ice breakup to open water between 2008 and 2010. Bowhead whales began their northward spring migration around 27 May (median day-of-the-year departure date 147, interquartile range 141153) and were distributed broadly in northern and central Disko Bay in water depths between 100 and 400 m. Humpback whales arrived in Disko Bay no later than 2 June and were located in shallow water (<100 m) along the coasts of the mainland or Disko Island. Trends in departure date from Disko Bay were significant for bowhead whales (∼15 d later, p < 0.001) between two periods: 20012006 and 20082010. Many species are predicted to arrive earlier in the Arctic and to expand their range northwards with reduced sea ice and increasing temperatures under climate change. Quantifying the spatial and temporal relationships between co-occurring Arctic and Subarctic top predators allows for baseline insight to be gained on how climate change might alter interspecies interactions. © 2012 International Council for the Exploration of the Sea. Published by Oxford University Press. All rights reserved.
Bowman J.S.,University of Washington |
Rasmussen S.,Technical University of Denmark |
Blom N.,Technical University of Denmark |
Deming J.W.,University of Washington |
And 2 more authors.
ISME Journal | Year: 2012
Dramatic decreases in the extent of Arctic multiyear ice (MYI) suggest this environment may disappear as early as 2100, replaced by ecologically different first-year ice. To better understand the implications of this loss on microbial biodiversity, we undertook a detailed census of the microbial community in MYI at two sites near the geographic North Pole using parallel tag sequencing of the 16S rRNA gene. Although the composition of the MYI microbial community has been characterized by previous studies, microbial community structure has not been. Although richness was lower in MYI than in underlying surface water, we found diversity to be comparable using the Simpson and Shannon's indices (for Simpson t=0.65, P=0.56; for Shannon t=0.25, P=0.84 for a Student's t-test of mean values). Cyanobacteria, comprising 6.8% of reads obtained from MYI, were observed for the first time in Arctic sea ice. In addition, several low-abundance clades not previously reported in sea ice were present, including the phylum TM7 and the classes Spartobacteria and Opitutae. Members of Coraliomargarita, a recently described genus of the class Opitutae, were present in sufficient numbers to suggest niche occupation within MYI. © 2012 International Society for Microbial Ecology All rights reserved.
Kjellerup S.,Technical University of Denmark |
Kjellerup S.,Greenland Institute of Natural Resources |
Kiorboe T.,Technical University of Denmark
Biology Letters | Year: 2012
Small cruising Zooplankton depend on remote prey detection and active prey capture for efficient feeding. Direct, passive interception of prey is inherently very inefficient at low Reynolds numbers because the viscous boundary layer surrounding the approaching predator will push away potential prey. Yet, direct interception has been proposed to explain how rapidly cruising, blind copepods feed on non-motile phytoplankton prey. Here, we demonstrate a novel mechanism for prey detection in a cruising copepod, and describe how motile and non-motile prey are discovered by hydromechanical and tactile or, likely, chemical cues, respectively. © 2011 The Royal Society.
Wieland K.,Technical University of Denmark |
Siegstad H.,Greenland Institute of Natural Resources
Marine Ecology Progress Series | Year: 2012
Survey estimates of northern shrimp Pandalus borealis biomass in West Greenland waters increased from about 178 000 t in 1998 to about 598 000 t in 2003. The increase in stock size was preceded by several consecutive years in which recruitment was substantially above average. Recruitment has been poor since then despite record high levels of female stock biomass. Rickertype stock-recruitment functions did not indicate that the variability in recruitment was related to female biomass. Multiple regression analysis revealed that mean female length, ambient bottom temperature and biomass of Greenland halibut Reinhardtius hippoglossoides had the most important effect on the variations of the 'recruit per female biomass' time series for the years 1993 to 2011. Variables which did not contribute significantly to the model included biomass of Atlantic cod Gadus morhua. This can be explained by the low stock size of Atlantic cod throughout the major part of the study period. The final model explained 83% of the variation in the recruit per female biomass index. However, the observations for 5 out of the 19 years considered in the present study were outside the 95% confidence interval of the fitted model, possibly due to a mismatch between the timing of larval hatch and the timing of the phytoplankton bloom, which could not adequately be addressed due to data limitations. © Inter-Research 2012.
Witting L.,Greenland Institute of Natural Resources
Population Ecology | Year: 2013
While it is known that population cycles are driven by delayed density-dependent feedbacks, the search for a common feedback mechanism in natural populations with cyclic dynamics has remained unresolved for almost a century. To identify the existence and cause of delayed feedbacks I apply six age- and sex-structured population dynamics models to seven species of baleen whales (suborder Mysticeti) that were heavily depleted by past commercial whaling. The six models include a predator-prey model with killer whale (Orcinus orca) as the predator, and five singe-species models based on (1) exponential growth, (2) density-regulated growth, (3) density-regulated growth with depensation, (4) delayed density-regulated growth and (5) selection-delayed dynamics. The latter model has a density-regulated growth rate that is accelerated and decelerated by the intra-specific natural selection that arises from the density-dependent competitive interactions between the individuals in the population. Essential parameters are estimated by a Bayesian statistical framework, and it is shown that baleen whales have a delayed recovery relative to density-regulated growth. The time-lag is not explained by depensation, or by interactions with prey or predators. It is instead resolved by a selection-delayed acceleration of the intrinsic growth rate. The results are discussed in relation to the literature on cyclic dynamics, and it is noted (1) that selection-delayed dynamics is both theoretically and empirically sufficient for cyclic population dynamics, (2) that it is widespread in natural populations owing to the widespread occurrence of otherwise unexplained phenotypic cycles in populations with cyclic dynamics, and (3) that there is a lack of empirical evidence showing that predator-prey interactions is a sufficient cause for the cyclic dynamics of natural populations. The conclusion stresses the importance of intra-specific delays in cyclic dynamics, and suggests that it is the acceleration of the growth rate, and not the growth rate itself, that is determined by the density-dependent environment. © 2013 The Society of Population Ecology and Springer Japan.
Mortensen J.,Greenland Institute of Natural Resources |
Lennert K.,Greenland Institute of Natural Resources |
Bendtsen J.,Greenland Institute of Natural Resources |
Rysgaard S.,Greenland Institute of Natural Resources
Journal of Geophysical Research: Oceans | Year: 2011
Recent warming of Subpolar Mode Water off Greenland has been suggested to accelerate the mass loss from tidal outlet glaciers of the Greenland Ice Sheet. We present a comprehensive analysis of water masses, dynamics, and interannual hydrographic variability in Godthåbsfjord, a sill fjord in contact with tidal outlet glaciers on the west coast of Greenland. Through seasonal observations we recognize an intermediate baroclinic circulation mode driven by tidal currents and an associated important local heat source for the fjord. During summer this results in significant warming and freshening of the intermediate layer of the main fjord, and the increase in heat content is equivalent to melting of ∼2.1 km3 of glacial ice. This is comparable to ∼8 km3 glacial ice discharge estimated from the Kangiata Nunta Sermia calving front per year. During winter the external heat source in the West Greenland Current enters the fjord as intermittent inflows of either cold (<2°C) or warm (>2°C) dense water in pulses of 1 to 3 months duration. Four distinct circulation modes are observed in the fjord, of which all can contribute to glacial ice melt. An important aspect of the ice distribution in the fjord is that only a minor fraction is exported out of the fjord. Copyright 2011 by the American Geophysical Union.