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Glaciers distinct from the Greenland and Antarctic ice sheets cover an area of approximately 706,000 square kilometres globally.sup.1, with an estimated total volume of 170,000 cubic kilometres, or 0.4 metres of potential sea-level-rise equivalent.sup.2. Retreating and thinning glaciers are icons of climate change.sup.3 and affect regional runoff.sup.4 as well as global sea level.sup.5,6. In past reports from the Intergovernmental Panel on Climate Change, estimates of changes in glacier mass were based on the multiplication of averaged or interpolated results from available observations of a few hundred glaciers by defined regional glacier areas.sup.7-10. For data-scarce regions, these results had to be complemented with estimates based on satellite altimetry and gravimetry.sup.11. These past approaches were challenged by the small number and heterogeneous spatiotemporal distribution of in situ measurement series and their often unknown ability to represent their respective mountain ranges, as well as by the spatial limitations of satellite altimetry (for which only point data are available) and gravimetry (with its coarse resolution). Here we use an extrapolation of glaciological and geodetic observations to show that glaciers contributed 27 [plus or minus] 22 millimetres to global mean sea-level rise from 1961 to 2016. Regional specific-mass-change rates for 2006-2016 range from -0.1 metres to -1.2 metres of water equivalent per year, resulting in a global sea-level contribution of 335 [plus or minus] 144 gigatonnes, or 0.92 [plus or minus] 0.39 millimetres, per year. Although statistical uncertainty ranges overlap, our conclusions suggest that glacier mass loss may be larger than previously reported.sup.11. The present glacier mass loss is equivalent to the sea-level contribution of the Greenland Ice Sheet.sup.12, clearly exceeds the loss from the Antarctic Ice Sheet.sup.13, and accounts for 25 to 30 per cent of the total observed sea-level rise.sup.14. Present mass-loss rates indicate that glaciers could almost disappear in some mountain ranges in this century, while heavily glacierized regions will continue to contribute to sea-level rise beyond 2100. The largest collection so far of glaciological and geodetic observations suggests that glaciers contributed about 27 millimetres to sea-level rise from 1961 to 2016, at rates of ice loss that could see the disappearance of many glaciers this century., Author(s): M. Zemp [sup.1] , M. Huss [sup.2] [sup.3] , E. Thibert [sup.4] , N. Eckert [sup.4] , R. McNabb [sup.5] , J. Huber [sup.1] , M. Barandun [sup.3] , [...]

Author(s): P. D. A. Kraaijenbrink (corresponding author) [1]; M. F. P. Bierkens [1, 2]; A. F. Lutz [3]; W. W. Immerzeel [1, 4] Glaciers in the high mountains of Asia [...]

A moraine chronology determined by surface exposure dating shows that glaciers in the northern tropical Andes expanded to a larger extent during the Antarctic cold reversal (14,500 to 12,900 years ago) than during the Younger Dryas stadial (12,800 to 11,500 years ago), contrary to previous studies; as a result, previous chronologies and climate interpretations from tropical glaciers may need to be revisited. Glaciation in the tropical Andes The Younger Dryas was a cold period immediately prior to the present warm interglacial period. There is clear evidence that it occurred throughout much of the Northern Hemisphere, but its global extent remains debatable. Prior work in the tropical Andes suggested extensive glacial advances during the Younger Dryas. Vincent Favier and colleagues present new cosmogenic dating of glacial deposits -- and a reassessment of existing datasets from other glaciated Andean landscapes -- to show that instead, maximal glacial advances took place in the preceding Antarctic cold reversal. Rather than a major advance, the Younger Dryas now appears to have been associated with modest glacial retreat. The Younger Dryas stadial, a cold event spanning 12,800 to 11,500 years ago, during the last deglaciation, is thought to coincide with the last major glacial re-advance in the tropical Andes.sup.1. This interpretation relies mainly on cosmic-ray exposure dating of glacial deposits. Recent studies, however, have established new production rates.sup.2,3,4 for cosmogenic .sup.10Be and .sup.3He, which make it necessary to update all chronologies in this region.sup.1,5,6,7,8,9,10,11,12,13,14,15 and revise our understanding of cryospheric responses to climate variability. Here we present a new .sup.10Be moraine chronology in Colombia showing that glaciers in the northern tropical Andes expanded to a larger extent during the Antarctic cold reversal (14,500 to 12,900 years ago) than during the Younger Dryas. On the basis of a homogenized chronology of all .sup.10Be and .sup.3He moraine ages across the tropical Andes, we show that this behaviour was common to the northern and southern tropical Andes. Transient simulations with a coupled global climate model suggest that the common glacier behaviour was the result of Atlantic meridional overturning circulation variability superimposed on a deglacial increase in the atmospheric carbon dioxide concentration. During the Antarctic cold reversal, glaciers advanced primarily in response to cold sea surface temperatures over much of the Southern Hemisphere. During the Younger Dryas, however, northern tropical Andes glaciers retreated owing to abrupt regional warming in response to reduced precipitation and land-surface feedbacks triggered by a weakened Atlantic meridional overturning circulation. Conversely, glacier retreat during the Younger Dryas in the southern tropical Andes occurred as a result of progressive warming, probably influenced by an increase in atmospheric carbon dioxide. Considered with evidence from mid-latitude Andean glaciers.sup.16, our results argue for a common glacier response to cold conditions in the Antarctic cold reversal exceeding that of the Younger Dryas., Author(s): V. Jomelli [sup.1] , V. Favier [sup.2] , M. Vuille [sup.3] , R. Braucher [sup.4] , L. Martin [sup.5] , P.-H. Blard [sup.5] , C. Colose [sup.3] , D. [...]

Ice loss and raised sea levels The Canadian Arctic Archipelago contains one-third of the global volume of land ice outside the ice sheets, but its contribution to sea-level change is largely unknown. Gardner et al. use three independent techniques to reveal that mass loss from the archipelago was 92 [plus or minus]12 gigatonnes per year in 2007-09, about three times greater than in 2004-06, and coincident with warmer summer temperatures. The record is too short to allow a firm conclusion on longer-term trends, but it is clear that the Canadian Arctic Archipelago is a significant contributor to sea-level rise. Mountain glaciers and ice caps are contributing significantly to present rates of sea level rise and will continue to do so over the next century and beyond.sup.1,2,3,4,5. The Canadian Arctic Archipelago, located off the northwestern shore of Greenland, contains one-third of the global volume of land ice outside the ice sheets.sup.6, but its contribution to sea-level change remains largely unknown. Here we show that the Canadian Arctic Archipelago has recently lost 61 [plus or minus] 7 gigatonnes per year (Gt yr.sup.-1) of ice, contributing 0.17 [plus or minus] 0.02 mm yr.sup.-1 to sea-level rise. Our estimates are of regional mass changes for the ice caps and glaciers of the Canadian Arctic Archipelago referring to the years 2004 to 2009 and are based on three independent approaches: surface mass-budget modelling plus an estimate of ice discharge (SMB+D), repeat satellite laser altimetry (ICESat) and repeat satellite gravimetry (GRACE). All three approaches show consistent and large mass-loss estimates. Between the periods 2004-2006 and 2007-2009, the rate of mass loss sharply increased from 31 [plus or minus] 8 Gt yr.sup.-1 to 92 [plus or minus] 12 Gt yr.sup.-1 in direct response to warmer summer temperatures, to which rates of ice loss are highly sensitive (64 [plus or minus] 14 Gt yr.sup.-1 per 1 K increase). The duration of the study is too short to establish a long-term trend, but for 2007-2009, the increase in the rate of mass loss makes the Canadian Arctic Archipelago the single largest contributor to eustatic sea-level rise outside Greenland and Antarctica., Author(s): Alex S. Gardner [sup.1] [sup.2] , Geir Moholdt [sup.3] [sup.4] , Bert Wouters [sup.5] , Gabriel J. Wolken [sup.6] , David O. Burgess [sup.7] , Martin J. Sharp [sup.1] [...]

An active microbial assemblage cycles sulfur in a sulfate-rich, ancient marine brine beneath Taylor Glacier, an outlet glacier of the East Antarctic Ice Sheet, with Fe(lll) serving as the terminal electron acceptor. Isotopic measurements of sulfate, water, carbonate, and ferrous iron and functional gene analyses of adenosine 5'-phosphosulfate reductase imply that a microbial consortium facilitates a catalytic sulfur cycle. These metabolic pathways result from a limited organic carbon supply because of the absence of contemporary photosynthesis, yielding a subglacial ferrous brine that is anoxic but not sulfidic. Coupled biogeochemical processes below the glacier enable subglacial microbes to grow in extended isolation, demonstrating how analogous organic-starved systems, such as Neoproterozoic oceans, accumulated Fe(II) despite the presence of an active sulfur cycle.

Author(s): Tanguy Bertrand [1]; Franois Forget (corresponding author) [1] Pluto has a variety of surface frosts and landforms as well as a complex atmosphere [1]. There is ongoing geological activity [...]

Evidence from high-sedimentation-rate South Atlantic deep-sea cores indicates that global and Southern Ocean carbon budget shifts preceded thermohaline circulation changes during the last ice age initiation and termination and that these were preceded by ice-sheet growth and retreat, respectively. No consistent lead-lag relationships are observed during abrupt millennial warming events during the last ice age, allowing for the possibility that ocean circulation triggered some millenial climate changes. At the major glacial-interglacial transitions, the global carbon budget and thermohaline ocean circulation responded sequentially to the climate changes that forced the growth and decline of continental ice sheets., Records of past global climate preserve evidence of large-scale changes in temperature and ice volume at glacial-interglacial boundaries. Although the timing of ice ages is broadly driven by Milankovich orbital [...]