Climate Changes Documented in Ice Core Records from Third Pole Glaciers, with Emphasis on the Guliya Ice Cap in the Western Kunlun Mountains over the Last 100 Years

NASA Astrophysics Data System (ADS)

Thompson, L. G.; Yao, T.; Beaudon, E.; Mosley-Thompson, E.; Davis, M. E.; Kenny, D. V.; Lin, P. N.

2016-12-01

The Third Pole (TP) is a rapidly warming region containing 100,000 km2 of ice cover that collectively holds one of Earth's largest stores of freshwater that feeds Asia's largest rivers and helps sustain 1.5 billion people. Information on the accelerating warming in the region, its impact on the glaciers and subsequently on future water resources is urgently needed to guide mitigation and adaptation policies. Ice core histories collected over the last three decades across the TP demonstrate its climatic complexity and diversity. Here we present preliminary results from the flagship project of the Third Pole Environment Program, the 2015 Sino-American cooperative ice core drilling of the Guliya ice cap in the Kunlun Mountains in the western TP near the northern limit of the region influenced by the southwest monsoon. Three ice cores, each 51 meters in length, were recovered from the summit ( 6700 masl) while two deeper cores, one to bedrock ( 310 meters), were recovered from the plateau ( 6200 masl). Across the ice cap the net balance (accumulation) has increased annually by 2.3 cm of water equivalent from 1963-1992 to 1992-2015, and average oxygen isotopic ratios (δ18O) have enriched by 2‰. This contrasts with the recent ablation on the Naimona'nyi glacier located 540 km south of Guliya in the western Himalaya. Borehole temperatures in 2015 on the Guliya plateau have warmed substantially in the upper 30 meters of the ice compared to temperatures in 1992, when the first deep-drilling of the Guliya plateau was conducted. Compared with glaciers in the northern and western TP, the Himalayan ice fields are more sensitive to both fluctuations in the South Asian Monsoon and rising temperatures in the region. We examine the climatic changes of the last century preserved in ice core records from sites throughout the TP and compare them with those reconstructed for earlier warm epochs, such as the Medieval Climate Anomaly ( 950-1250 AD), the early Holocene "Hypsithermal" ( 5 to 9 kyr BP) and the Eemian (present only in Guliya). The latter epoch is the latest period when Earth may have been as warm as today and thus serves as an analog for the developing greenhouse world.

Tropical Glaciers in the Common Era: Papua, Indonesia, Quelccaya Ice Cap, Peru and Kilimanjaro, Tanzania

NASA Astrophysics Data System (ADS)

Thompson, L. G.; Mosley-Thompson, E. S.; Davis, M. E.

2011-12-01

High-resolution ice core stratigraphic records of δ18O (temperature proxy) demonstrate that the current warming at high elevations in mid- to lower latitudes is unprecedented for at least the last two millennia, although at many sites the Early Holocene was much warmer than at present. Here we discuss the interaction of El Niño-Southern Oscillation (ENSO) variability and warming trends as recorded in ice core records from high-altitude tropical glaciers and the implications of the warming trends for the future of these glaciers. ENSO has strong impacts on meteorological phenomena that either directly or indirectly affect most regions on the planet and their populations, particularly throughout the Tropics. Here we examine similarities and differences among ice core records from Papua (Indonesia), Quelccaya Ice Cap (Peru) and Kilimanjaro (Tanzania). Quelccaya, Earth's largest tropical ice cap, has provided continuous, annually-resolved proxy records of climatic and environmental variability preserved in many measurable parameters, especially oxygen and hydrogen isotopic ratios (δ18O, δD) and the net mass balance (accumulation) spanning the last 1800 years. The remarkable similarity between changes in the highland and coastal cultures of Peru and climate variability in the Andes, especially with regard to precipitation, implies a strong connection between prehistoric human activities and climate in this region. The well-documented ice loss on Quelccaya, Kilimanjaro in eastern Africa and the ice fields near Puncak Jaya in Papua, Indonesia presents a possible analog for glacier response in the tropics during the Holocene. The ongoing melting of these ice fields is consistent with model predictions of a vertical amplification of temperature in the Tropics. A sequence of over 50 recently exposed, rooted, soft-bodied plant deposits collected between 2002 and 2011 from the retreating margins of the Quelccaya ice cap provide a longer term perspective for the recent glacier retreat. The ongoing glacier retreat in the Tropics and associated loss of natural resources has dire implications for people living in these areas. These recent changes are examined in the context of the Common Era from a glacier derived paleoclimate perspective as recorded in the glaciers on the world's highest mountains.

Fluid core size of Mars from detection of the solar tide

NASA Technical Reports Server (NTRS)

Yoder, C. F.; Konopliv, A. S.; Yuan, D. N.; Standish, E. M.; Folkner, W. M.

2003-01-01

The solar tidal deformation of Mars, measured by its k2 potential Love number, has been obtained from an analysis of Mars Global Surveyor radio tracking. The observed k2 of 0.153 +/- 0.017 is large enough to rule out a solid iron core and so indicates that at least the outer part of the core is liquid. The inferred core radius is between 1520 and 1840 kilometers and is independent of many interior properties, although partial melt of the mantle is one factor that could reduce core size. Ice-cap mass changes can be deduced from the seasonal variations in air pressure and the odd gravity harmonic J3, given knowledge of cap mass distribution with latitude. The south cap seasonal mass change is about 30 to 40% larger than that of the north cap.

Fluid Core Size of Mars from Detection of the Solar Tide

NASA Astrophysics Data System (ADS)

Yoder, C. F.; Konopliv, A. S.; Yuan, D. N.; Standish, E. M.; Folkner, W. M.

2003-04-01

The solar tidal deformation of Mars, measured by its k2 potential Love number, has been obtained from an analysis of Mars Global Surveyor radio tracking. The observed k2 of 0.153 +/- 0.017 is large enough to rule out a solid iron core and so indicates that at least the outer part of the core is liquid. The inferred core radius is between 1520 and 1840 kilometers and is independent of many interior properties, although partial melt of the mantle is one factor that could reduce core size. Ice-cap mass changes can be deduced from the seasonal variations in air pressure and the odd gravity harmonic J3, given knowledge of cap mass distribution with latitude. The south cap seasonal mass change is about 30 to 40% larger than that of the north cap.

Holocene fluctuations of Quelccaya Ice Cap, Peru based on lacustrine and surficial geologic archives

NASA Astrophysics Data System (ADS)

Stroup, J. S.; Kelly, M. A.; Lowell, T. V.; Beal, S. A.; Smith, C. A.

2013-12-01

Peru's Quelccaya Ice Cap (QIC; 13.9°S, 70.8°W, ~5200-5670 m asl) is an important site for understanding tropical paleoclimate, mainly because of annually layered ice cores that provide an ~1800 year long record of tropical paleoclimatic conditions (e.g., Thompson et al., 2013). Here, we present a detailed record of QIC fluctuations using surficial deposits and lake sediments that extend back to late glacial time. We compare the late Holocene records of QIC 10Be-dated moraines and ice core data with lake sediments from a nearby glacially fed lake to establish the framework we use to interpret a Holocene long sediment record from a glacially fed lake. We also examine sediments from a nearby non-glacial lake to constrain non-glacial clastic input. We collected two ~5 m-long sediment cores, one from Laguna Challpacocha, which is currently fed by QIC meltwater, and one from the Laguna Yanacocha, which has not received QIC meltwater since ~12.3 ka. Changes in magnetic susceptibility, loss on ignition, bulk density and X-ray fluorescence chemistry combined with 14C and 210Pb chronologies provide information about sediment transported to the lakes. Retreat from the late Holocene extent defined by the 10Be-dated moraine record (~0.52 ka) is contemporaneous with a sharp transition from organic to clastic sedimentation in the Challpacocha core at ~ 0.52 ka. This implies that glacially-sourced clastic sedimentation, as tracked by loss on ignition, Ti counts and bulk density, increased during ice cap recession. Based on these same proxy data, we suggest the following Holocene history of QIC: QIC receded from the Challpacocha basin by ~10.6 ka. Increased clastic sedimentation at 8.2 - 4.1, 3.6 - 2.7 ka and from 0.55 ka - present are interpreted as times of ice cap recession. The increased clastic sedimentation at ~8.2 - 4.1 ka is consistent with surficial deposits near the present-day ice margin that indicate that at ~7.0 - 4.6 ka QIC was smaller than at present (Buffen et al., 2009). Clastic sedimentation may reflect the glacier thermal regime. Relic plants now being uncovered by the receding QIC (Thompson et al., 2006, 2013) suggest advance of cold-based ice that did not produce significant meltwater or rock flour. Striations, also present on the landscape, indicate warm-based ice conditions, which would produce meltwater and rock flour. We suggest that these striations were likely produced during ice cap retreat. A small QIC during early and middle Holocene time and large QIC during late Holocene time is similar to the Holocene extents of many Northern Hemisphere glaciers and apparently follows the pattern of Northern Hemisphere summer insolation.

Ice core evidence for extensive melting of the greenland ice sheet in the last interglacial.

PubMed

Koerner, R M

1989-05-26

Evidence from ice at the bottom of ice cores from the Canadian Arctic Islands and Camp Century and Dye-3 in Greenland suggests that the Greenland ice sheet melted extensively or completely during the last interglacial period more than 100 ka (thousand years ago), in contrast to earlier interpretations. The presence of dirt particles in the basal ice has previously been thought to indicate that the base of the ice sheets had melted and that the evidence for the time of original growth of these ice masses had been destroyed. However, the particles most likely blew onto the ice when the dimensions of the ice caps and ice sheets were much smaller. Ice texture, gas content, and other evidence also suggest that the basal ice at each drill site is superimposed ice, a type of ice typical of the early growth stages of an ice cap or ice sheet. If the present-day ice masses began their growth during the last interglacial, the ice sheet from the earlier (Illinoian) glacial period must have competely or largely melted during the early part of the same interglacial period. If such melting did occur, the 6-meter higher-than-present sea level during the Sangamon cannot be attributed to disintegration of the West Antarctic ice sheet, as has been suggested.

The Subsurface Ice Probe (SIPR): A Low-Power Thermal Probe for the Martian Polar Layered Deposits

NASA Technical Reports Server (NTRS)

Cardell, G.; Hecht, M. H.; Carsey, F. D.; Engelhardt, H.; Fisher, D.; Terrell, C.; Thompson, J.

2004-01-01

The distinctive layering visible in images from Mars Global Surveyor of the Martian polar caps, and particularly in the north polar cap, indicates that the stratigraphy of these polar layered deposits may hold a record of Martian climate history covering millions of years. On Earth, ice sheets are cored to retrieve a pristine record of the physical and chemical properties of the ice at depth, and then studied in exacting detail in the laboratory. On the Martian north polar cap, coring is probably not a practical method for implementation in an autonomous lander. As an alternative, thermal probes that drill by melting into the ice are feasible for autonomous operation, and are capable of reasonable approximations to the scientific investigations performed on terrestrial cores, while removing meltwater to the surface for analysis. The Subsurface Ice Probe (SIPR) is such a probe under development at JPL. To explore the dominant climate cycles, it is postulated that tens of meters of depth should be profiled, as this corresponds to the vertical separation of the major layers visible in the MOC images [1]. Optical and spectroscopic analysis of the layers, presumably demarcated by embedded dust and possibly by changes in the ice properties, would contribute to the construction of a chronology. Meltwater analysis may be used to determine the soluble chemistry of the embedded dust, and to monitor gradients of atmospheric gases, particularly hydrogen and oxygen, and isotopic variations that reflect atmospheric conditions at the time the layer was deposited. Thermal measurements can be used to determine the geothermal gradient and the bulk mechanical properties of the ice.

Holocene glacier and climate variations in Vestfirðir, Iceland, from the modeling of Drangajökull ice cap

NASA Astrophysics Data System (ADS)

Anderson, Leif S.; Flowers, Gwenn E.; Jarosch, Alexander H.; Aðalgeirsdóttir, Guðfinna Th; Geirsdóttir, Áslaug; Miller, Gifford H.; Harning, David J.; Thorsteinsson, Thorsteinn; Magnússon, Eyjólfur; Pálsson, Finnur

2018-06-01

Drangajökull is a maritime ice cap located in northwest (Vestfirðir) Iceland. Drangajökull's evolution is therefore closely linked to atmospheric and ocean variability. In order to better constrain the Holocene climate and glacier history of Vestfirðir we model the past evolution of Drangajökull ice cap. Simulations from 10 ka to present are forced by general circulation model output, ice-core-based temperature reconstructions, and sea-surface temperature reconstructions. Based on these 10-thousand year simulations, Drangajökull did not persist through the Holocene. We estimate that air temperatures were 2.5-3.0 °C higher during the Holocene Thermal Maximum than the local 1960-1990 average. Simulations support Drangajökull's late Holocene inception between 2 and 1 ka, though intermittent ice likely occupied cirques as early as 2.6 ka. Drangajökull is primarily a Little Ice Age ice cap: it expanded between 1300 and 1750 CE, with the most rapid growth occurring between 1600 and 1750 CE. The maximum Holocene extent of Drangajökull occurred between 1700 and 1925 CE, despite the lowest late Holocene temperatures, occurring between 1650 and 1720 CE. Between 1700 and 1925 CE temperatures were likely 0.6-0.8 °C lower than the 1950-2015 reference temperature. The modern equilibrium line altitude (ELA) is bracketed by topographic thresholds: a 1 °C temperature increase from the modern ELA would eliminate the ice cap's accumulation area, while a reduction of 0.5 °C would lead to the rapid expansion of the ice cap across Vestfirðir. The proximity of Drangajökull to topographic thresholds may explain its late inception and rapid expansion during the Little Ice Age.

Climate Change: The Evidence and Our Options

ERIC Educational Resources Information Center

Thompson, Lonnie G.

2010-01-01

Glaciers serve as early indicators of climate change. Over the last 35 years, our research team has recovered ice-core records of climatic and environmental variations from the polar regions and from low-latitude high-elevation ice fields from 16 countries. The ongoing widespread melting of high-elevation glaciers and ice caps, particularly in low…

Central Tibetan Plateau atmospheric trace metals contamination: A 500-year record from the Puruogangri ice core.

PubMed

Beaudon, Emilie; Gabrielli, Paolo; Sierra-Hernández, M Roxana; Wegner, Anna; Thompson, Lonnie G

2017-12-01

A ~500-year section of ice core (1497-1992) from the Puruogangri ice cap has been analyzed at high resolution for 28 trace elements (TEs: Ag, Al, As, Ba, Bi, Cd, Co, Cr, Cs, Cu, Fe, Ga, Li, Mg, Mn, Na, Nb, Ni, Pb, Rb, Sb, Sn, Sr, Ti, Tl, U, V and Zn) to assess different atmospheric contributions to the ice and provide a temporal perspective on the diverse atmospheric influences over the central Tibetan Plateau (TP). At least two volcanic depositions have significantly impacted the central TP over the past 500years, possibly originating from the Billy Mitchell (1580, Papua New Guinea) and the Parker Peak (1641, Philippines) eruptions. A decreasing aeolian dust input to the ice cap allowed the detection of an atmospheric pollution signal. The anthropogenic pollution contribution emerges in the record since the early 1900s (for Sb and Cd) and increases substantially after 1935 (for Ag, Zn, Pb, Cd and Sb). The metallurgy (Zn, Pb and steel smelting) emission products (Cd, Zn, Pb and Ag) from the former Soviet Union and especially from central Asia (e.g., Kyrgyzstan, Kazakhstan) likely enhanced the anthropogenic deposition to the Puruogangri ice cap between 1935 and 1980, suggesting that the westerlies served as a conveyor of atmospheric pollution to central Tibet. The impact of this industrial pollution cumulated with that of the hemispheric coal and gasoline combustion which are respectively traced by Sb and Pb enrichment in the ice. The Chinese steel production accompanying the Great Leap Forward (1958-1961) and the Chinese Cultural Revolution (1966-1976) is proposed as a secondary but proximal source of Pb pollution affecting the ice cap between 1958 and 1976. The most recent decade (1980-1992) of the enrichment time series suggests that Puruogangri ice cap recorded the early Sb, Cd, Zn, Pb and Ag pollution originating from developing countries of South (i.e., India) and East (i.e., China) Asia and transported by the summer monsoonal circulation. Published by Elsevier B.V.

Early Holocene deglaciation of Drangajökull, Vestfirðir, Iceland

NASA Astrophysics Data System (ADS)

Harning, David J.; Geirsdóttir, Áslaug; Miller, Gifford H.; Zalzal, Kate

2016-12-01

The status of Icelandic ice caps during the early Holocene provides important constraints on North Atlantic climate and the mechanisms behind natural climate variability. A recent study postulates that Drangajökull on Vestfirðir, Iceland, persisted through the Holocene Thermal Maximum (HTM, 7.9-5.5 ka) and may be a relic from the last glacial period. We test this hypothesis with a suite of sediment cores from threshold lakes both proximal and distal to the ice cap's modern margin. Distal lakes document rapid early Holocene deglaciation from the coast and across the highlands south of the glacier. Sediment from Skorarvatn, a lake to the north of Drangajökull, shows that the northern margin of the ice cap reached a size comparable to its contemporary limit by ∼10.3 ka. Two southeastern lakes with catchments extending well beneath modern Drangajökull confirm that by ∼9.2 ka, the ice cap was reduced to ∼20% of its current area. A continuous 10.3ka record of biological productivity from Skorarvatn's sediment indicates local peak warmth occurred between 9 and 6.9 ka. The combination of warm and dry summers on Vestfirðir suggests that Drangajökull very likely melted completely shortly after 9.2 ka, similar to most other Icelandic ice caps.

Continuous non-marine inputs of per- and polyfluoroalkyl substances to the High Arctic: a multi-decadal temporal record

NASA Astrophysics Data System (ADS)

Pickard, Heidi M.; Criscitiello, Alison S.; Spencer, Christine; Sharp, Martin J.; Muir, Derek C. G.; De Silva, Amila O.; Young, Cora J.

2018-04-01

Perfluoroalkyl acids (PFAAs) are persistent, in some cases, bioaccumulative compounds found ubiquitously within the environment. They can be formed from the atmospheric oxidation of volatile precursor compounds and undergo long-range transport (LRT) through the atmosphere and ocean to remote locations. Ice caps preserve a temporal record of PFAA deposition making them useful in studying the atmospheric trends in LRT of PFAAs in polar or mountainous regions, as well as in understanding major pollutant sources and production changes over time. A 15 m ice core representing 38 years of deposition (1977-2015) was collected from the Devon Ice Cap in Nunavut, providing us with the first multi-decadal temporal ice record in PFAA deposition to the Arctic. Ice core samples were concentrated using solid phase extraction and analyzed by liquid and ion chromatography methods. Both perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs) were detected in the samples, with fluxes ranging from < LOD to 141 ng m-2 yr-1. Our results demonstrate that the PFCAs and perfluorooctane sulfonate (PFOS) have continuous and increasing deposition on the Devon Ice Cap, despite recent North American and international regulations and phase-outs. We propose that this is the result of on-going manufacture, use and emissions of these compounds, their precursors and other newly unidentified compounds in regions outside of North America. By modelling air mass transport densities, and comparing temporal trends in deposition with production changes of possible sources, we find that Eurasian sources, particularly from Continental Asia, are large contributors to the global pollutants impacting the Devon Ice Cap. Comparison of PFAAs to their precursors and correlations of PFCA pairs showed that deposition of PFAAs is dominated by atmospheric formation from volatile precursor sources. Major ion analysis confirmed that marine aerosol inputs are unimportant to the long-range transport mechanisms of these compounds. Assessments of deposition, homologue profiles, ion tracers, air mass transport models, and production and regulation trends allow us to characterize the PFAA depositional profile on the Devon Ice Cap and further understand the LRT mechanisms of these persistent pollutants.

Earth's Climate History from Glaciers and Ice Cores

NASA Astrophysics Data System (ADS)

Thompson, Lonnie

2013-03-01

Glaciers serve both as recorders and early indicators of climate change. Over the past 35 years our research team has recovered climatic and environmental histories from ice cores drilled in both Polar Regions and from low to mid-latitude, high-elevation ice fields. Those ice core -derived proxy records extending back 25,000 years have made it possible to compare glacial stage conditions in the Tropics with those in the Polar Regions. High-resolution records of δ18O (in part a temperature proxy) demonstrate that the current warming at high elevations in the mid- to lower latitudes is unprecedented for the last two millennia, although at many sites the early Holocene was warmer than today. Remarkable similarities between changes in the highland and coastal cultures of Peru and regional climate variability, especially precipitation, imply a strong connection between prehistoric human activities and regional climate. Ice cores retrieved from shrinking glaciers around the world confirm their continuous existence for periods ranging from hundreds to thousands of years, suggesting that current climatological conditions in those regions today are different from those under which these ice fields originated and have been sustained. The ongoing widespread melting of high-elevation glaciers and ice caps, particularly in low to middle latitudes, provides strong evidence that a large-scale, pervasive and, in some cases, rapid change in Earth's climate system is underway. Observations of glacier shrinkage during the 20th and 21st century girdle the globe from the South American Andes, the Himalayas, Kilimanjaro (Tanzania, Africa) and glaciers near Puncak Jaya, Indonesia (New Guinea). The history and fate of these ice caps, told through the adventure, beauty and the scientific evidence from some of world's most remote mountain tops, provide a global perspective for contemporary climate. NSF Paleoclimate Program

Central Tibetan Plateau atmospheric trace metals contamination: a 500-year record from the Puruogangri ice core

NASA Astrophysics Data System (ADS)

Beaudon, E.; Gabrielli, P.; Sierra Hernandez, R.; Wegner, A.; Thompson, L. G.

2017-12-01

Since the 1980s, Asia has experienced enormous industrial development from rapid population growth, industrialization and consequent large-scale environmental changes. The inherent generated atmospheric pollution currently contributes to half of all Earth's anthropogenic trace metals emissions. Asian trace metal aerosols, when deposited on glaciers of the surrounding mountains of the Tibetan Plateau (TP), leave a characteristic chemical fingerprint. Interpreting trace element (TE) records from glaciers implies a thorough comprehension of their provenance and temporal variability. It is then essential to discriminate the TEs' natural background components from their anthropogenic components. Here we present 500-year TE records from the Puruogangri ice core (Tibet, China) that provide a highly resolved account of the impact of past atmospheric influences, environmental processes and human activities on the central TP. A decreasing aeolian dust input to the ice cap allowed the detection of an atmospheric pollution signal. The anthropogenic pollution contribution emerges in the record since the early 1900s and increases substantially after 1935. The metallurgy (Zn, Pb and steel smelting) emission products from the former Soviet Union and especially from central Asia likely enhanced the anthropogenic deposition to the Puruogangri ice cap between 1935 and 1980, suggesting that the westerlies served as a conveyor of atmospheric pollution to central Tibet. The impact of this industrial pollution cumulated with that of the hemispheric coal and gasoline combustion which are respectively traced by Sb and Pb enrichment in the ice. The Chinese steel production accompanying the Great Leap Forward (1958-1961) and the Chinese Cultural Revolution (1966-1976) is proposed as a secondary but proximal source of Pb pollution affecting the ice cap between 1958 and 1976. The most recent decade (1980-1992) of the enrichment time series suggests that Puruogangri ice cap recorded the early Sb, Cd, Zn, Pb and Ag pollution originating from developing countries of South (i.e., India) and East (i.e., China) Asia and transported by the summer monsoonal circulation.

High Arctic Holocene temperature record from the Agassiz ice cap and Greenland ice sheet evolution

PubMed Central

Lecavalier, Benoit S.; Fisher, David A.; Milne, Glenn A.; Vinther, Bo M.; Tarasov, Lev; Lacelle, Denis; Main, Brittany; Zheng, James; Bourgeois, Jocelyne; Dyke, Arthur S.

2017-01-01

We present a revised and extended high Arctic air temperature reconstruction from a single proxy that spans the past ∼12,000 y (up to 2009 CE). Our reconstruction from the Agassiz ice cap (Ellesmere Island, Canada) indicates an earlier and warmer Holocene thermal maximum with early Holocene temperatures that are 4–5 °C warmer compared with a previous reconstruction, and regularly exceed contemporary values for a period of ∼3,000 y. Our results show that air temperatures in this region are now at their warmest in the past 6,800–7,800 y, and that the recent rate of temperature change is unprecedented over the entire Holocene. The warmer early Holocene inferred from the Agassiz ice core leads to an estimated ∼1 km of ice thinning in northwest Greenland during the early Holocene using the Camp Century ice core. Ice modeling results show that this large thinning is consistent with our air temperature reconstruction. The modeling results also demonstrate the broader significance of the enhanced warming, with a retreat of the northern ice margin behind its present position in the mid Holocene and a ∼25% increase in total Greenland ice sheet mass loss (∼1.4 m sea-level equivalent) during the last deglaciation, both of which have implications for interpreting geodetic measurements of land uplift and gravity changes in northern Greenland. PMID:28512225

A comparison of Holocene fluctuations of the eastern and western margins of the Greenland Ice Sheet

NASA Astrophysics Data System (ADS)

Levy, L.; Kelly, M. A.; Lowell, T. V.; Hall, B. L.; Applegate, P. J.; Howley, J.; Axford, Y.

2013-12-01

Determining how the Greenland Ice Sheet (GrIS) responded to past temperature fluctuations is important for assessing its future stability in a changing climate. We present a record of the Holocene extents of the western GrIS margin near Kangerlussuaq (67.0°N, 50.7°W) and compare this with the past fluctuations of Bregne ice cap (71°N, 25.6° W), a small ice cap in the Scoresby Sund region 90 km from the eastern GrIS margin, to examine the mechanisms that influenced past ice margin fluctuations. The past extents of the Bregne ice cap are a proxy for the climatic conditions that influenced the nearby GrIS margin. We used glacial geomorphic mapping, 10Be dating of boulders and bedrock, and sediment cores from proglacial and non-glacial lakes. In western Greenland, 10Be ages on the Keglen moraines, 13 km west of the current GrIS margin and the Ørkendalen moraines, ≤2 km west of the current ice margin date to 7.3 × 0.1 ka (n=6) and 6.8 × 0.3 ka (n=9), respectively. Fresh moraines, ≤50 m from the current ice margin date to AD 1830-1950 and are likely associated with advances during the Little Ice Age (LIA). In some areas, the LIA moraines lie stratigraphically above the Ørkendalen moraines, indicating the GrIS was inboard of the Ørkendalen limit from 6.8 ka to the 20th century. In eastern Greenland, 10Be ages show that Bregne ice cap retreated within its late Holocene limit by 10.7 ka. A lack of clastic sediment in a proglacial lake suggests the ice cap was smaller or completely absent from ~10-2.6 ka. A snowline analysis indicates that temperatures ~0.5°C warmer than present would render the entire ice cap into an ablation zone. Glacial silts in the proglacial lake at ~2.6 and ~1.9 cal kyr BP to present indicate advances of Bregne ice cap. Fresh moraines ≤200 m of Bregne ice cap were deposited ≤2.6 cal kyr BP and mark the largest advance of the Holocene. Both the western GrIS margin and Bregne ice cap were influenced by Northern Hemisphere summer insolation during the Holocene. The western GrIS margin retreated significantly and Bregne ice cap likely disappeared during the warm early to middle Holocene. 10Be ages (10.7 ka) outboard of the late Holocene moraines at Bregne ice cap compared to those outside of the LIA moraines near Kangerlussuaq (6.8 ka) differ by ~4 kyr. This disparity in ages may have been caused by a large late Holocene advance in eastern Greenland, or perhaps the western GrIS margin retreated farther inland during the middle Holocene. Decreasing Northern Hemisphere summer insolation during the late Holocene, combined with a strong, cold East Greenland Current near Scoresby Sund may have influenced a significant ice cap advance. The temporal pattern of the responses of the eastern and western ice margins to Holocene climate changes may be indicative of how the GrIS will respond to future changes.

Differences in community composition of bacteria in four deep ice sheets in western China

NASA Astrophysics Data System (ADS)

An, L.; Chen, Y.; Xiang, S.-R.; Shang, T.-C.; Tian, L.-De

2010-02-01

Microbial community patterns vary in glaciers world wide, presenting unique responses to global climatic and environmental changes. Four bacterial clone libraries were established by 16S rRNA gene amplification from four ice layers along the 42-m-long ice core MuztB drilled from the Muztag Ata Glacier. A total of 152 bacterial sequences obtained from the ice core MuztB were phylogenetically compared with the 71 previously reported sequences from three ice cores extracted from ice caps Malan, Dunde, and Puruoganri. The six functional clusters Flavisolibacter, Flexibacter (Bacteroidetes), Acinetobacter, Enterobacter (Gammaproteobacteria), Planococcus/Anoxybacillus (Firmicutes), and Propionibacter/Luteococcus (Actinobacteria) frequently occurred along the Muztag Ata Glacier profile. Sequence analysis showed that most of the sequences from the ice core clustered with those from cold environments, and the sequences from the same glacier formed a distinct cluster. Moreover, bacterial communities from the same location or similarly aged ice formed a cluster, and were clearly separate from those from other geographically isolated glaciers. In a summary, the findings provide preliminary evidence of zone distribution of microbial community, support our hypothesis of the spatial and temporal biogeography of microorganisms in glacial ice.

Quelccaya Ice Core Evidence of Widespread Atmospheric Pollution from Colonial Metallurgy after the Spanish Conquest of South America (1532 AD)

NASA Astrophysics Data System (ADS)

Gabrielli, P.; Uglietti, C.; Cooke, C. A.; Thompson, L. G.

2014-12-01

A few ice core records recovered from remote arctic regions suggest a widespread impact of toxic trace elements (Pb, Cu, Sb, As and Bi) to the North Hemisphere atmosphere prior to the onset of the Industrial Revolution (1780s-1830s). In the Southern Hemisphere, evidence for preindustrial trace element emissions are, to date, limited to sediment cores recovered from lakes located within the immediate airshed of major metallurgical centers of South America. Thus it remains unresolved whether they could have had a larger scale impact. Here, we present an annually resolved ice core record of anthropogenic trace element deposition from the remote drilling site of the Quelccaya Ice Cap (Peru) that spans 793-1989 AD. During the pre-Inca period (i.e., prior to ~1450 AD) the deposition of trace elements was dominated by the fallout of aeolian dust from the deglaciated margins of the ice cap and of ash from occasional volcanic eruptions. In contrast, the ice core record indicates a clear anthropogenic signal emerging after the onset of large scale colonial mining and metallurgy (1532-1820 AD), ~300 years prior to the Industrial Revolution during the last part of the Little Ice Age. This shift was coincidental with a major technological transition for silver extraction (1572 AD), from lead-based smelting to mercury amalgamation, that initiated a major increase in ore mining and milling that likely resulted in an increase of metallic dust emissions. While atmospheric trace element deposition resulting from colonial metallurgy was certainly much larger than during the pre-Colonial period, trace element fallout during the Colonial era was still several factors lower than during the 20th century, when the construction of the trans-Andean railway and highways promoted a widespread societal and industrial development of South America.

Diversity of Holocene life forms in fossil glacier ice

PubMed Central

Willerslev, Eske; Hansen, Anders J.; Christensen, Bent; Steffensen, Jørgen Peder; Arctander, Peter

1999-01-01

Studies of biotic remains of polar ice caps have been limited to morphological identification of plant pollen and spores. By using sensitive molecular techniques, we now demonstrate a much greater range of detectable organisms; from 2000- and 4000-year-old ice-core samples, we obtained and characterized 120 clones that represent at least 57 distinct taxa and reveal a diversity of fungi, plants, algae, and protists. The organisms derive from distant sources as well as from the local arctic environment. Our results suggest that additional taxa may soon be readily identified, providing a plank for future studies of deep ice cores and yielding valuable information about ancient communities and their change over time. PMID:10393940

Paleoenvironmental reconstructions of Nettilling Lake area (Baffin Island, Nunavut): A multi-proxy analysis.

NASA Astrophysics Data System (ADS)

Beaudoin, Anne; Pienitz, Reinhard; Francus, Pierre; Zdanowicz, Christian; St-Onge, Guillaume

2014-05-01

The paleoclimate and paleolimnological history of several Arctic regions remains poorly known. This is the case for the area around Nettilling Lake (Baffin Island, Nunavut), the largest lake of the Canadian Arctic Archipelago. To reconstruct the past environmental history of this area, a highly innovative multi-proxy approach combining physical, magnetic, chemical and biological properties preserved in lake sediments was used. One particular goal of this study was to investigate the possible coupling between sedimentation processes observed in the lake and melt rates of nearby Penny Ice Cap. A 1-m long sediment core was retrieved from a small bay in the northeastern part of Nettilling Lake during the summer of 2010. This sampling area was chosen based on the hypothesis that incoming glacial meltwaters from Penny Ice Cap would leave a strong climate-modulated signal that would be reflected in the sedimentary sequence. The core was analyzed by both non-destructive (X-radiography (X-ray), microfluorescence-X (µ-XRF), magnetic susceptibility) and destructive (Loss On Ignition, grain size, water content, thin sections, diatoms) techniques. Radiometric AMS 14C and 210Pb/137Cs age determinations, as well as paleomagnetic measurements, were used to develop the core chronology, yielding an estimated bottom age of approximately 1365 AD. The sedimentation rate (0.15 cm.yr-1) in Nettilling Lake was found to be high compared to other Arctic lakes, due to inputs of highly turbid meltwaters from Penny Ice Cap with high suspended sediment loads. Significant correlations were found between geochemical profiles of elements linked to detrital inputs (Si, Ti, K, Ca) and melt rates from Penny Ice Cap since the 19th century. This suggests that variations in detrital elements in Nettilling Lake sediments might be used as an indirect indicator of regional climate fluctuations (e.g., summer temperatures) that determine glacier melt rates.

Differences in community composition of bacteria in four glaciers in western China

NASA Astrophysics Data System (ADS)

An, L. Z.; Chen, Y.; Xiang, S.-R.; Shang, T.-C.; Tian, L.-D.

2010-06-01

Microbial community patterns vary in glaciers worldwide, presenting unique responses to global climatic and environmental changes. Four bacterial clone libraries were established by 16S rRNA gene amplification from four ice layers along the 42-m-long ice core MuztB drilled from the Muztag Ata Glacier. A total of 151 bacterial sequences obtained from the ice core MuztB were phylogenetically compared with the 71 previously reported sequences from three ice cores extracted from ice caps Malan, Dunde, and Puruogangri. Six phylogenetic clusters Flavisolibacter, Flexibacter (Bacteroidetes), Acinetobacter, Enterobacter (Gammaproteobacteria), Planococcus/Anoxybacillus (Firmicutes), and Propionibacter/Luteococcus (Actinobacteria) frequently occurred along the Muztag Ata Glacier profile, and their proportion varied by seasons. Sequence analysis showed that most of the sequences from the ice core clustered with those from cold environments, and the sequence clusters from the same glacier more closely grouped together than those from the geographically isolated glaciers. Moreover, bacterial communities from the same location or similarly aged ice formed a cluster, and were clearly separate from those from other geographically isolated glaciers. In summary, the findings provide preliminary evidence of zonal distribution of microbial community, and suggest biogeography of microorganisms in glacier ice.

Annually resolved ice core records of tropical climate variability over the past ~1800 years.

PubMed

Thompson, L G; Mosley-Thompson, E; Davis, M E; Zagorodnov, V S; Howat, I M; Mikhalenko, V N; Lin, P-N

2013-05-24

Ice cores from low latitudes can provide a wealth of unique information about past climate in the tropics, but they are difficult to recover and few exist. Here, we report annually resolved ice core records from the Quelccaya ice cap (5670 meters above sea level) in Peru that extend back ~1800 years and provide a high-resolution record of climate variability there. Oxygen isotopic ratios (δ(18)O) are linked to sea surface temperatures in the tropical eastern Pacific, whereas concentrations of ammonium and nitrate document the dominant role played by the migration of the Intertropical Convergence Zone in the region of the tropical Andes. Quelccaya continues to retreat and thin. Radiocarbon dates on wetland plants exposed along its retreating margins indicate that it has not been smaller for at least six millennia.

Correlating Ice Cores from Quelccaya Ice Cap with Chronology from Little Ice Age Glacial Extents

NASA Astrophysics Data System (ADS)

Stroup, J. S.; Kelly, M. A.; Lowell, T. V.

2010-12-01

Proxy records indicate Southern Hemisphere climatic changes during the Little Ice Age (LIA; ~1300-1850 AD). In particular, records of change in and around the tropical latitudes require attention because these areas are sensitive to climatic change and record the dynamic interplay between hemispheres (Oerlemans, 2005). Despite this significance, relatively few records exist for the southern tropics. Here we present a reconstruction of glacial fluctuations of Quelccaya Ice Cap (QIC), Peruvian Andes, from pre-LIA up to the present day. In the Qori Kalis valley, extensive sets of moraines exist beginning with the 1963 AD ice margin (Thompson et al., 2006) and getting progressively older down valley. Several of these older moraines can be traced and are continuous with moraines in the Challpa Cocha valley. These moraines have been dated at <1050-1350-AD (Mercer and Palacios, 1977) and interpreted to have been deposited during the Little Ice Age. We present a new suite of surface exposure and radiocarbon dates collected in 2008 and 2009 that constrain the ages of these moraines. Preliminary 10Be ages of boulder surfaces atop the moraines range from ~350-1370 AD. Maximum and minimum-limiting radiocarbon ages bracketing the moraines are ~0-1800 AD. The chronology of past ice cap extents are correlated with ice core records from QIC which show an accumulation increase during ~1500-1700 AD and an accumulation decrease during ~1720-1860 AD (Thompson et al., 1985; 1986; 2006). In addition, other proxy records from Peru and the tropics are correlated with the records at QIC as a means to understand climate conditions during the LIA. This work forms the basis for future modeling of the glacial system during the LIA at QIC and for modeling of past temperature and precipitation regimes at high altitude in the tropics.

Palaeoglaciology of the Alexander Island ice cap, western Antarctic Peninsula, reconstructed from marine geophysical and core data

NASA Astrophysics Data System (ADS)

Graham, Alastair G. C.; Smith, James A.

2012-03-01

The glacial history of the continental shelf northwest of Alexander Island is not well known, due mainly to a lack of targeted marine data on Antarctica's palaeo-ice sheets in their inter-ice-stream areas. Recently it has been argued that the region was ice-free at the Last Glacial Maximum (LGM) and thus a potential site for glacial refugia. In this paper, multibeam swath bathymetry, sub-bottom profiles and sediment cores are used to map the Alexander Island sector of the Antarctic Peninsula margin, in order to reconstruct the shelf's palaeoglaciology. Sea-floor bedforms provide evidence that an independent ice cap persisted on Alexander Island through the LGM and deglaciation. We show that this ice cap drained via two major, previously-undescribed tidewater outlets (Rothschild and Charcot Glaciers) sourced from an ice dome centred over the west of the island and near-shore areas. The glaciers grounded along deep, fjord-like cross-shelf troughs to within at least ˜10-20 km of the shelf edge, and probably reached the shelf break. Only one small outer-shelf zone appears to have remained free of ice throughout an otherwise extensive LGM. During retreat, grounding-line geomorphology indicates periodic stabilisation of Charcot Glacier on the mid-shelf after 13,500 cal yrs BP, while Rothschild Glacier retreated across its mid-shelf by 14,450 cal yrs BP. The timing of these events is in phase with retreat in nearby Marguerite Trough, and we take this as evidence of a common history and forcing with the Antarctic Peninsula Ice Sheet. The fine details of ice flow documented by our new reconstruction highlight the importance of capturing complex ice flow patterns in models (e.g. in inter-stream areas), for understanding how region-specific parts of Antarctica may change in the future. Moreover, the reconstruction shows that glacial refugia, if present, cannot have been extensive on the Alexander Island shelf at the LGM as indicated by previous biological studies; instead, we argue that any ice-free refugia were probably restricted to isolated outer-shelf pockets, that opened, closed, or were maintained through diachronous ice-sheet advance and retreat.

Radar Detection of Layering in Ice: Experiments on a Constructed Layered Ice Sheet

NASA Astrophysics Data System (ADS)

Carter, L. M.; Koenig, L.; Courville, Z.; Ghent, R. R.; Koutnik, M. R.

2016-12-01

The polar caps and glaciers of both Earth and Mars display internal layering that preserves a record of past climate. These layers are apparent both in optical datasets (high resolution images, core samples) and in ground penetrating radar (GPR) data. On Mars, the SHARAD (Shallow Radar) radar on the Mars Reconnaissance Orbiter shows fine layering that changes spatially and with depth across the polar caps. This internal layering has been attributed to changes in fractional dust contamination due to obliquity-induced climate variations, but there are other processes that can lead to internal layers visible in radar data. In particular, terrestrial sounding of ice sheets compared with core samples have revealed that ice density and composition differences account for the majority of the radar reflectors. The large cold rooms and ice laboratory facility at the U.S. Army Cold Regions Research and Engineering Laboratory (CRREL) provide us a unique opportunity to construct experimental ice sheets in a controlled setting and measure them with radar. In a CRREL laboratory, we constructed a layered ice sheet that is 3-m deep with a various snow and ice layers with known dust concentrations (using JSC Mars-1 basaltic simulant) and density differences. These ice sheets were profiled using a commercial GPR, at frequencies of 200, 400 and 900 MHz, to determine how the radar profile changes due to systematic and known changes in snow and ice layers, including layers with sub-wavelength spacing. We will report results from these experiments and implications for interpreting radar-detected layering in ice on Earth and Mars.

Lake Sediment Records as an Indicator of Holocene Fluctuations of Quelccaya Ice Cap, Peru and Regional Climate

NASA Astrophysics Data System (ADS)

Stroup, J. S.; Kelly, M. A.; Lowell, T. V.; Beal, S. A.; Smith, C. A.; Baranes, H. E.

2012-12-01

The past fluctuations of Quelccaya Ice Cap, (QIC; 13°S, 70°W, 5200 m asl) located in the southeastern Peruvian Andes, provide a record of tropical climate since the last glacial-interglacial transition. A detailed surficial geomorphic record of past glacial extents developed over the last several decades (e.g. Mercer and Palacios 1977; Buffen et al. 2009; Kelly et al. 2012 accepted) demonstrates that QIC is a dynamic glacial system. These records show that the ice cap was larger than present and retreating by ~11,500 yr BP, and smaller than present between ~7,000 and ~4,600 yr BP. The most recent advance occurred during the late Holocene (Little Ice Age;LIA), dated with 10Be surface exposure ages (510±90 yrs (n = 8)) (Stroup et al. in prep.). This overrode earlier deposits obscuring a complete Holocene record; we aim to address the gaps in glacial chronology using the sedimentary record archived in lakes. We retrieved two sets cores (8 and 5 m-long) from Laguna Challpacocha (13.91°S, 70.86°W, 5040 m asl), a lake that currently receives meltwater from QIC. Four radiocarbon ages from the cores suggest a continuous record dating to at least ~10,500 cal. yr BP. Variations in magnetic susceptibility, percent organic and inorganic carbon, bulk density, grayscale and X-ray fluorescence chemistry indicate changes in the amount of clastic sediment deposition. We interpret clastic sediments to have been deposited from ice cap meltwater, thus indicating more extensive ice. Clastic sediments compose the top of the core from 4 to 30 cm depth, below there is a sharp transition to organic sediments radiocarbon dated to (500±30 and 550±20 cal. yr BP). The radiocarbon ages are similar to the 10Be dated (LIA) glacial position. At least three other clastic units exist in the core; dating to ~2600-4300, ~4800-7300 and older then ~10,500 cal. yr BP based on a linear age model with four radiocarbon dates. We obtained two, ~4 m long, cores from Laguna Yanacocha (13.95°S,70.87°W, 4910 m asl), a lake that has not received glacial meltwater since late glacial time. We used the clastic sediment record to determine the input from non-glacial sources, representing ambient climate. This information tests our hypothesis that increased clastic sediment is from a glacial source in the Challpacocha record. The Yanacocha cores are composed primarily of organic-rich sediment with little clastic sediment. Eight radiocarbon ages in stratigraphic order indicate a continuous sedimentation in the lake since 11,240±90 cal. yr BP. Till at the base of the core indicates likely ice recession from the basin at this time. Variations in magnetic susceptibility, percent organic and inorganic carbon, bulk density, and gray scale suggest only minor changes in sedimentation relative to those in the Challpacocha core. Our new continuous lake sediment record provides complementary data to the discontinuous records of QIC Holocene extents as marked by moraines and exposed sections (e.g. Buffen et al. 2009; Thompson et al. 2006). Our record has some similarities with the nearby lacustrine record from Laguna Pacococha, which also receives meltwater from QIC (Rodbell and Seltzer, 2000; Abbott et al., 2003).

Ice crystallization in ultrafine water-salt aerosols: nucleation, ice-solution equilibrium, and internal structure.

PubMed

Hudait, Arpa; Molinero, Valeria

2014-06-04

Atmospheric aerosols have a strong influence on Earth's climate. Elucidating the physical state and internal structure of atmospheric aqueous aerosols is essential to predict their gas and water uptake, and the locus and rate of atmospherically important heterogeneous reactions. Ultrafine aerosols with sizes between 3 and 15 nm have been detected in large numbers in the troposphere and tropopause. Nanoscopic aerosols arising from bubble bursting of natural and artificial seawater have been identified in laboratory and field experiments. The internal structure and phase state of these aerosols, however, cannot yet be determined in experiments. Here we use molecular simulations to investigate the phase behavior and internal structure of liquid, vitrified, and crystallized water-salt ultrafine aerosols with radii from 2.5 to 9.5 nm and with up to 10% moles of ions. We find that both ice crystallization and vitrification of the nanodroplets lead to demixing of pure water from the solutions. Vitrification of aqueous nanodroplets yields nanodomains of pure low-density amorphous ice in coexistence with vitrified solute rich aqueous glass. The melting temperature of ice in the aerosols decreases monotonically with an increase of solute fraction and decrease of radius. The simulations reveal that nucleation of ice occurs homogeneously at the subsurface of the water-salt nanoparticles. Subsequent ice growth yields phase-segregated, internally mixed, aerosols with two phases in equilibrium: a concentrated water-salt amorphous mixture and a spherical cap-like ice nanophase. The surface of the crystallized aerosols is heterogeneous, with ice and solution exposed to the vapor. Free energy calculations indicate that as the concentration of salt in the particles, the advance of the crystallization, or the size of the particles increase, the stability of the spherical cap structure increases with respect to the alternative structure in which a core of ice is fully surrounded by solution. We predict that micrometer-sized particles and nanoparticles have the same equilibrium internal structure. The variation of liquid-vapor surface tension with solute concentration is a key factor in determining whether a solution-embedded ice core or vapor-exposed ice cap is the equilibrium structure of the aerosols. In agreement with experiments, we predict that the structure of mixed-phase HNO3-water particles, representative of polar stratospheric clouds, consists of an ice core surrounded by freeze-concentrated solution. The results of this work are important to determine the phase state and internal structure of sea spray ultrafine aerosols and other mixed-phase particles under atmospherically relevant conditions.

Early Deglaciation of Drangajökull, Vestfirðir, Iceland: Smaller than Present by 9.2 ka

NASA Astrophysics Data System (ADS)

Harning, D.; Geirsdottir, A.; Miller, G. H.; Zalzal, K.

2016-12-01

The Holocene histories of Iceland's largest ice caps suggest rapid early Holocene deglaciation and disappearance by 9 ka, other than possible small remnants of Vatnajökull. The least documented is Drangajökull, Vestfirðir, NW Iceland, where our team has been working since 2010. A recent study claims Drangajökull behaved differently than the other Iceland ice caps, deglaciating much later, and persisting through the Holocene Thermal Maximum (HTM). We test this postulate through a suite of sediment cores from threshold lakes both proximal and distal to the ice cap's contemporary margin. Distal lakes document rapid early Holocene deglaciation across the southern highland plateau, with the northern margin of the ice cap reaching a size comparable to Drangajökull's contemporary limit by 10.3 ka. A proximal lake to the north records a transient readvance at 9.6 ka, likely in association with meltwater pulses from the disintegrating Laurentide Ice Sheet (LIS). Two other southeastern proximal lakes, whose catchments extend well beneath the modern ice cap, demonstrate that Drangajökull was already smaller than present before 9.2 ka. Supporting evidence for local early Holocene warmth is derived from biological summer temperature proxies in a lake record, with age control (tephra/14C) demonstrating continuous sediment accumulation from 10.3 ka to present. Peak warmth (HTM) inferred from elevated algal productivity occurred between 8.9 and 7.2 ka. The record of terrestrial warmth closely aligns with regional SST and precipitation records that together with lake sediment characteristics provide firm evidence that Drangajökull responded similarly to Iceland's other large ice caps. Drangajökull was smaller than its contemporary margin before 9.2 ka, and likely disappeared entirely during the warmer and drier summers between 9 and 7 ka, reforming in the Late Holocene.

CALICE: Calibrating Plant Biodiversity in Glacier Ice

NASA Astrophysics Data System (ADS)

Festi, Daniela; Cristofori, Antonella; Vernesi, Cristiano; Zerbe, Stefan; Wellstein, Camilla; Maggi, Valter; Oeggl, Klaus

2017-04-01

The objective of the project is to reconstruct plant biodiversity and its trend archived in Alpine glacier ice by pollen and eDNA (environmental DNA) during the last five decades by analyzing a 40 m ice core. For our study we chose the Adamello glacier (Trentino - Südtirol, Lombardia) because of i) the good preservation conditions for pollen and eDNA in ice, ii) the thickness of the ice cap (270m) and iii) the expected high time resolution. The biodiversity estimates gained by pollen analysis and eDNA will be validated by historical biodiversity assessments mainly based on vegetation maps, aerial photos and vegetation surveys in the catchment area of the Adamello glacier for the last five decades. This historical reconstruction of biodiversity trends will be performed on a micro-, meso- and macro-scale (5, 20-50 and 50-100 Km radius, respectively). The results will serve as a calibration data set on biodiversity for future studies, such as the second step of the coring by the POLLiCE research consortium (pollice.fmach.it). In fact, arrangements are currently been made to drill the complete ice cap and retrieve a 270 m thick core which has the potential to cover a time span of minimum 400 years up to several millennia. This second stage will extend the time scale and enable the evaluation of dissimilarity/similarity of modern biodiversity in relation to Late Holocene trends. Finally, we believe this case study has the potential to be applied in other glaciated areas to evaluate biodiversity for large regions (e.g. central Asian mountain ranges, Tibet and Tian Shan or the Andes).

Episodic expansion of Drangajökull, Vestfirðir, Iceland, over the last 3 ka culminating in its maximum dimension during the Little Ice Age

NASA Astrophysics Data System (ADS)

Harning, David J.; Geirsdóttir, Áslaug; Miller, Gifford H.; Anderson, Leif

2016-11-01

Non-linear climate change is often linked to rapid changes in ocean circulation, especially around the North Atlantic. As the Polar Front fluctuated its latitudinal position during the Holocene, Iceland's climate was influenced by both the warm Atlantic currents and cool, sea ice-bearing Arctic currents. Drangajökull is Iceland's fifth largest ice cap. Climate proxies in lake sediment cores, dead vegetation emerging from beneath the ice cap, and moraine segments identified in a new DEM constrain the episodic expansion of the ice cap over the past 3 ka. Collectively, our data show that Drangajökull was advancing at ∼320 BCE, 180 CE, 560 CE, 950 CE and 1400 CE and in a state of recession at ∼450 CE, 1250 CE and after 1850 CE. The Late Holocene maximum extent of Drangajökull occurred during the Little Ice Age (LIA), occupying 262 km2, almost twice its area in 2011 CE and ∼20% larger than recent estimates of its LIA dimensions. Biological proxies from the sediment fill in a high- and low-elevation lake suggest limited vegetation and soil cover at high elevations proximal to the ice cap, whereas thick soil cover persisted until ∼750 CE at lower elevations near the coast. As Drangajökull expanded into the catchment of the high-elevation lake beginning at ∼950 CE, aquatic productivity diminished, following a trend of regional cooling supported by proxy records elsewhere in Iceland. Correlations between episodes of Drangajökull's advance and the documented occurrence of drift ice on the North Icelandic Shelf suggest export and local production of sea ice influenced the evolution of NW Iceland's Late Holocene climate.

Detecting Near-Surface Ice Formation Over Time Using the Kennaugh Elements Approach From TerraSAR-X

NASA Astrophysics Data System (ADS)

Fernandes, L.

2016-12-01

The summer melting has increased substantially at higher elevations on the Canadian Arctic ice caps. The resulting meltwater percolates into the upper layers of snow and firn and then refreeze, building massive ice bodies. It seems likely that these within-firn ice bodies now limit meltwater penetration into the firn and may be creating a feedback whereby the fraction of melt that runs off to the ocean is increasing. Although changes in firn structure as presence of ice layers and ice bodies are well documented over the Devon ice cap, the firm has shown that it exerts a crucial role to predict more accurately the contribution of small ice caps to the sea level rise. However it is still challenging to assess the extent of these features within the shallow subsurface using ice cores and GPR (Ground Penetrating Radar) data collected along a limited number of linear transects. Studying changes in the distribution of ice bodies' formation over time has the potential to provide information about how the growth of ice bodies in the firn is affecting the pattern of water flow in the firn layer. The objective is investigate the potential of Kennaugh Elements (KE) derived from x-band SAR (Synthetic Aperture Radar) for mapping the distribution and growth of large ice bodies within the firn and the evolution of their distribution over time. The evaluation of this method could reveal a new approach suitable for other glacierized regions that would reduce the costs and amount of field work for studying such properties.

Atmospheric depositions of natural and anthropogenic trace elements on the Guliya ice cap (northwestern Tibetan Plateau) during the last 340 years

NASA Astrophysics Data System (ADS)

Sierra-Hernández, M. Roxana; Gabrielli, Paolo; Beaudon, Emilie; Wegner, Anna; Thompson, Lonnie G.

2018-03-01

A continuous record of 29 trace elements (TEs) has been constructed between 1650 and 1991 CE (Common Era) from an ice core retrieved in 1992 from the Guliya ice cap, on the northwestern Tibetan Plateau. Enrichments of Pb, Cd, Zn and Sb were detected during the second half of the 19th century and the first half of the 20th century (∼1850-1950) while enrichments of Sn (1965-1991), Cd and Pb (1975-1991) were detected during the second half of the 20th century. The EFs increased significantly by 20% for Cd and Sb, and by 10% for Pb and Zn during 1850-1950 relative to the pre-1850s. Comparisons of the Guliya TEs data with other ice core-derived and production/consumption data suggest that Northern Hemisphere coal combustion (primarily in Western Europe) is the likely source of Pb, Cd, Zn, and Sb during the 1850-1950 period. Coal combustion in Europe declined as oil replaced coal as the primary energy source. The European shift from coal to oil may have contributed to the observed Sn enrichment in ∼1965 (60% EF increase in 1975-1991), although regional fossil fuel combustion (coal and leaded gasoline) from western China, Central Asia, and South Asia (India, Nepal), as well as Sn mining/smelting in Central Asia, may also be possible sources. The post-1975 Cd and Pb enrichments (40% and 20% EF increase respectively in 1975-1991) may reflect emissions from phosphate fertilizers, fossil fuel combustion, and/or non-ferrous metal production, from western China, Central Asia, and/or South Asia. Leaded gasoline is likely to have also contributed to the post-1975 Pb enrichment observed in this record. The results strongly suggest that the Guliya ice cap has recorded long-distance emissions from coal combustion since the 1850s with more recent contributions from regional agriculture, mining, and/or fossil fuel combustion. This new Guliya ice core record of TEs fills a geographical gap in the reconstruction of the pollution history of this region that extends well beyond modern instrumental records.

Paleoclimatic significance of insoluble microparticle records from Canadian Arctic and Greenland ice cores

NASA Astrophysics Data System (ADS)

Zdanowicz, Christian Michel

1999-10-01

The past and present variability of climate in the Arctic region is investigated using ice core records of atmospheric dust (microparticles) and volcanic aerosols developed from the Canadian Arctic and Greenland. A high- resolution, 10 4-year long proxy record of atmospheric dust deposition is developed from an ice core (P95) drilled through the Penny Ice Cap, Baffin Island. Snowpit studies indicate that dust deposited on the Penny Ice Cap are representative of background mineral aerosol, and demonstrate that the variability of dust fallout is preserved in the P95 core at multi-annual to longer time scales. The P95 dust record reveals a significant increase in dust deposition on the Penny Ice Cap between ca 7500-5000 yr ago. This increase was driven by early to mid-/late Holocene transformations in the Northern Hemisphere landscape (ice cover retreat, postglacial land emergence) and climate (transition to colder, drier conditions) that led to an expansion of sources and enhanced eolian activity. Comparison between dust records in the P95 and GISP2 (Greenland) ice cores shows an increasing divergence between the two records beginning ca 7500 years ago. The effects of Northern Hemisphere atmospheric circulation and snow cover extent on atmospheric dust deposition in the Arctic are evaluated by comparing the P95 dust record with observational data. Changes in dust deposition are strongly linked to modes of the Northern Hemisphere winter circulation. Most prominently, an inverse relationship between the P95 dust record and the intensity of the winter Siberian High accounts for over 50% of the interannual variance of these two parameters over the period 1899-1995. On inter- to multi- annual time scales, the P95 dust record is significantly anticorrelated with variations in spring, and to a lesser extent fall, snow cover extent in the mid-latitude interior regions of Eurasia and North America. These relationships account for an estimated 10 to 20% of variance in the P95 dust record. An empirical orthogonal function (EOF) analysis is used to investigate patterns of temporal covariance among insoluble microparticles and major ions deposited in the GISP2 and P95 ice cores. Dust and major ions covary strongly in the GISP2 late glacial record but are uncorrelated in both the GISP2 and P95 Holocene records. Companion EOF analyses of the Holocene records identify distinctive covariance patterns among microparticles and/or major ions that are associated with certain aerosols types or with source-specific air masses reaching the Arctic, providing further evidence of increased regional-scale climatic and atmospheric variability over the last ~ 12,000 years. The atmospheric and climatic impact of the early Holocene eruption of Mount Mazama (Crater Lake, Oregon) is evaluated from the GISP2 ice core record of volcanically- derived sulfate and ash particles. The calendrical age of the eruption is determined to be 7627 +/- 150 cal yr B.P. The GISP2 sulfate record suggests a total stratospheric aerosol loading between 88 and 224 Mt spread over a ~ 6-year period following the eruption. From these figures, the Mount Mazama eruption is estimated to have depressed temperature by ~ 0.6 to 0.7°C at mid- to high northern latitudes. (Abstract shortened by UMI.)

A New Method for the Determination of Annual Sediment Fluxes from Varved Lake Sediments

NASA Astrophysics Data System (ADS)

Francus, P.; Massa, C.; Lapointe, F.

2013-12-01

Calculation of sediment mass accumulation rates instead of thickness accumulation is preferable for paleoclimatic reconstruction as it eliminates the effects of dilution and compaction. Annually laminated lake sediment sequences (varved) theoretically allow for the estimation of sediment fluxes at annual scale, but the calculation is limited by discrete bulk density measurements, often carried out at a much lower resolution (usually 1 cm) than the varves (ranging from 0.07 to 27.3 mm, average 1.84 mm according to Ojala et al. 2012). Since many years the development of automated logging instruments made available continuous and high resolution sediment property data, in a non-destructive fashion. These techniques can easily be used to extract the physical and chemical parameters of sediments at the varve scale (down to 100 μm). Here we present a robust method to calculate annual sediment fluxes from varved lake sediments by combining varves thickness measurements to core logging data, and provide an example for its applications. Several non-destructive densitometric methods applied to the Strathcona Lake sediment, northern Ellesmere Island, Canada (78°33'N; 82°05'W) were compared: Hounsfield Units from a CT-Scan, coherent/incoherent ratio and X-ray radiography (of both split core and sediment slabs, from an Itrax core Scanner), and gamma ray attenuation density. Core logging data were statistically compared to 400 discrete measurements of dry bulk density, wet bulk density and water content performed at 2 mm contiguous intervals. A very strong relationship was found between X-ray grey level on sediment slab and dry bulk density. Relative X-ray densities, at 100μm resolution, were then successfully calibrated against real densities. The final step consisted in binning the calibrated densities to the corresponding varve thickness and then to calculate the annual mass accumulation rates by multiplying the two parameters for each varve year. Strathcona Lake is located directly downstream of the Agassiz ice cap and contains laminated sediments whose accumulation is directly related to hydrological inputs generated by the melting of the ice cap. Over the last 65 years, annual sediment accumulation rates in Strathcona Lake documented an increase in high-energy hydrologic discharge events from 1990 to 2009. This timing is in agreement with evidence for an increase in the amount of melt on the adjacent Agassiz Ice Cap, as recorded in ice cores. A good correspondence was also found between annual mass accumulation rates and Eureka air temperature records, suggesting that temperature changes affected the extent of summer melting on the Agassiz Ice Cap, leading to high sediment yield to Strathcona Lake. Ojala, A.E.K., Francus, P., Zolitschka, B., Besonen, M. and Lamoureux, S.F. (2012) Characteristics of sedimentary varve chronologies - A review. Quaternary Science Reviews, 43, 45-60.

1500 Years of Annual Climate and Environmental Variability as Recorded in Bona-Churchill (Alaska) Ice Cores

NASA Astrophysics Data System (ADS)

Thompson, L. G.; Mosley-Thompson, E. S.; Zagorodnov, V.; Davis, M. E.; Mashiotta, T. A.; Lin, P.

2004-12-01

In 2003, six ice cores measuring 10.5, 11.5, 11.8, 12.4, 114 and 460 meters were recovered from the col between Mount Bona and Mount Churchill (61° 24'N; 141° 42'W; 4420 m asl). These cores have been analyzed for stable isotopic ratios, insoluble dust content and concentrations of major chemical species. Total Beta radioactivity was measured in the upper sections. The 460-meter core, extending to bedrock, captured the entire depositional record at this site where ice temperatures ranged from -24° C at 10 meters to -19.8° C at the ice/bedrock contact. The shallow cores allow assessment of surface processes under modern meteorological conditions while the deep core offers a ˜1500-year climate and environmental perspective. The average annual net balance is ˜~1000 mm of water equivalent and distinct annual signals in dust and calcium concentrations along with δ 18O allow annual resolution over most of the core. The excess sulfate record reflects many known large volcanic eruptions such as Katmai, Krakatau, Tambora, and Laki which allow validation of the time scale in the upper part of the core. The lower part of the core yields a history of earlier volcanic events. The 460-m Bona-Churchill ice core provides a detailed history of the `Little Ice Age' and medieval warm periods for southeastern Alaska. The source of the White River Ash will be discussed in light of the evidence from this core. The 460-m core also provides a long-term history of the dust fall that originates in north-central China. The annual ice core-derived climate records from southeastern Alaska will facilitate an investigation of the likelihood that the high resolution 1500-year record from the tropical Quelccaya Ice Cap (Peru) preserves a history of the variability of both the PDO and the Aleutian Low.

Assessment of the Relationship between Andean Ice Core Precipitation Indicators and Amazon River Discharge

NASA Astrophysics Data System (ADS)

Johnson, N.; Alsdorf, D.; Thompson, L.; Mosley-Thompson, E.; Melack, J.

2006-12-01

Prior to the last 100 years, there is a significant lack of hydrologic knowledge for the Amazon Basin. A 100- year record of discharge from the city of Manaus, located at the confluence of the Solimoes and Negro rivers, is the most complete record for the basin. Inundated wetlands play a key role in carbon out-gassing to the atmosphere whereas discharge from the Amazon River contributes about 20% of the total freshwater flux delivered to the world's oceans. As discharge (Q) and inundation are directly related to precipitation, we are developing a method to extend our understanding of Q and inundation into the 19^{th} century. Using proxy data preserved in Andean glaciers and ice caps and recovered from ice cores, annually resolved histories of δ^{18)O and mass accumulation are available. The latter is a proxy for local precipitation amount whereas δ18O is influenced by continental scale processes (i.e., evaporation, convection) as well as by temperature and hence, by varying climate regimes. We have correlated the accumulation and δ18O records from Core 1 drilled on the Quelccaya ice-cap in the southern Andes of Peru with the Manaus discharge data. As ice core annual layers correspond to the thermal year (in Peru, July to June of the following year) and the discharge records are kept daily (January to December), we averaged 365 days of Q data seeking the optimal correlation for each start and end date. The best statistical relationship between δ18O and Q (r = -0.41, p = < 0.001) is attained when Q is averaged from March 16 to March 15 of the following year. We also correlated 23 years of ENSO events, which are linked to both Amazon River discharge and ice core δ18O (r = -0.60, p = < 0.001). These linear relationships are used to create Amazon discharge for the 20^{th} century and to extrapolate Q into the 19^{th} century. Previously developed relationships between Q and mainstem inundated area are then used to estimate inundated area along the main Amazon channel for the past 200 years. The ice core-derived estimate of inundated area for the past 100 years compares well with the previous and more straightforward estimates based on discharge and remote sensing data.

Analysis of vanillic acid in polar ice cores as a biomass burning proxy - preliminary results from the Akademii Nauk Ice Cap in Siberia

NASA Astrophysics Data System (ADS)

Grieman, M. M.; Jimenez, R.; McConnell, J. R.; Fritzsche, D.; Saltzman, E. S.

2013-12-01

Biomass burning influences global climate change and the composition of the atmosphere. The drivers, effects, and climate feedbacks related to fire are poorly understood. Many different proxies have been used to reconstruct past fire frequency from lake sediments and polar ice cores. Reconstruction of historical trends in biomass burning is challenging because of regional variability and the qualitative nature of various proxies. Vanillic acid (4-hydroxy-3-methoxybenzoic acid) is a product of the combustion of conifer lignin that is known to occur in biomass burning aerosols. Biomass burning is likely the only significant source of vanillic acid in polar ice. In this study we describe an analytical method for quantifying vanillic acid in polar ice using HPLC with electrospray ionization and tandem mass spectrometric detection. The method has a detection limit of 100 pM and a precision of × 10% at the 100 pM level for analysis of 100 μl of ice melt water. The method was used to analyze more than 1000 discrete samples from the Akademii Nauk ice cap on Severnaya Zemlya in the high Russia Arctic (79°30'N, 97°45'E) (Fritzsche et al., 2002; Fritzsche et al., 2005; Weiler et al., 2005). The samples range in age over the past 2,000 years. The results show a mean vanillic acid concentration of 440 × 710 pM (1σ), with elevated levels during the periods from 300-600 and 1450-1550 C.E.

Rapid wastage of the Hazen Plateau ice caps, northeastern Ellesmere Island, Nunavut, Canada

NASA Astrophysics Data System (ADS)

Serreze, Mark C.; Raup, Bruce; Braun, Carsten; Hardy, Douglas R.; Bradley, Raymond S.

2017-01-01

Two pairs of small stagnant ice bodies on the Hazen Plateau of northeastern Ellesmere Island, the St. Patrick Bay ice caps and the Murray and Simmons ice caps, are rapidly shrinking, and the remnants of the St. Patrick Bay ice caps are likely to disappear entirely within the next 5 years. Vertical aerial photographs of these Little Ice Age relics taken during August of 1959 show that the larger of the St. Patrick Bay ice caps had an area of 7.48 km2 and the smaller one 2.93 km2; the Murray and Simmons ice caps covered 4.37 and 7.45 km2 respectively. Outlines determined from ASTER satellite data for July 2016 show that, compared to 1959, the larger and the smaller of the St. Patrick Bay ice caps had both been reduced to only 5 % of their former area, with the Murray and Simmons ice caps faring better at 39 and 25 %, likely reflecting their higher elevation. Consistent with findings from other glaciological studies in the Queen Elizabeth Islands, ASTER imagery in conjunction with past GPS surveys documents a strikingly rapid wastage of the St. Patrick Bay ice caps over the last 15 years. These two ice caps shrank noticeably even between 2014 and 2015, apparently in direct response to the especially warm summer of 2015 over northeastern Ellesmere Island. The well-documented recession patterns of the Hazen Plateau ice caps over the last 55+ years offer an opportunity to examine the processes of plant recolonization of polar landscapes.

Winter mass balance of Drangajökull ice cap (NW Iceland) derived from satellite sub-meter stereo images

NASA Astrophysics Data System (ADS)

Belart, Joaquín M. C.; Berthier, Etienne; Magnússon, Eyjólfur; Anderson, Leif S.; Pálsson, Finnur; Thorsteinsson, Thorsteinn; Howat, Ian M.; Aðalgeirsdóttir, Guðfinna; Jóhannesson, Tómas; Jarosch, Alexander H.

2017-06-01

Sub-meter resolution, stereoscopic satellite images allow for the generation of accurate and high-resolution digital elevation models (DEMs) over glaciers and ice caps. Here, repeated stereo images of Drangajökull ice cap (NW Iceland) from Pléiades and WorldView2 (WV2) are combined with in situ estimates of snow density and densification of firn and fresh snow to provide the first estimates of the glacier-wide geodetic winter mass balance obtained from satellite imagery. Statistics in snow- and ice-free areas reveal similar vertical relative accuracy (< 0.5 m) with and without ground control points (GCPs), demonstrating the capability for measuring seasonal snow accumulation. The calculated winter (14 October 2014 to 22 May 2015) mass balance of Drangajökull was 3.33 ± 0.23 m w.e. (meter water equivalent), with ∼ 60 % of the accumulation occurring by February, which is in good agreement with nearby ground observations. On average, the repeated DEMs yield 22 % less elevation change than the length of eight winter snow cores due to (1) the time difference between in situ and satellite observations, (2) firn densification and (3) elevation changes due to ice dynamics. The contributions of these three factors were of similar magnitude. This study demonstrates that seasonal geodetic mass balance can, in many areas, be estimated from sub-meter resolution satellite stereo images.

Molecular Markers in the Quelccaya Ice Cap, Peru Describe 20th Century Biomass Burning Variability

NASA Astrophysics Data System (ADS)

Makou, M. C.; Thompson, L. G.; Eglinton, T. I.; Montluçon, D. B.

2007-12-01

Organic geochemical analytical methods were applied to Andean ice core samples, resulting in a multi- molecular biomass burning record spanning 1915 to 2001 AD. The Quelccaya Ice Cap in Peru is situated on the eastern flank of the Andes at 14°S and is well situated to receive aeolian inputs of organic matter derived from Amazonian forest fire events. Compounds of interest, which occur in trace quantities in ice, were recovered by stir bar sorptive extraction and analyzed by gas chromatography/time-of-flight mass spectrometry coupled with thermal desorption. These methods permitted identification and quantitation of numerous biomarkers in sample volumes of as little as 10 ml. At least one wet and dry season sample was analyzed for every year. Observed biomarkers that may be derived from vegetation fires include several polycyclic aromatic hydrocarbons (PAHs), atraric acid, 2-ethylhexyl p-methoxycinnamate, and a range of other aromatic compounds. Abrupt changes in compound abundances were superimposed on decadal variability. Systematic offsets between wet and dry season abundances were not observed, suggesting that the biomass burning signal is not biased by seasonal depositional effects, such as dust delivery. Inputs likely reflect a combination of sources from anthropogenic burning of the Amazon rainforest as well as natural fires related to aridity, and include both high and low elevation vegetation. These compounds and techniques can be applied to older ice in this and other core locations as an independent estimate of aridity.

Recent Increases in Snow Accumulation and Decreases in Sea-Ice Concentration Recorded in a Coastal NW Greenland Ice Core

NASA Astrophysics Data System (ADS)

Osterberg, E. C.; Thompson, J. T.; Wong, G. J.; Hawley, R. L.; Kelly, M. A.; Lutz, E.; Howley, J.; Ferris, D. G.

2013-12-01

A significant rise in summer temperatures over the past several decades has led to widespread retreat of the Greenland Ice Sheet (GIS) margin and surrounding sea ice. Recent observations from geodetic stations and GRACE show that ice mass loss progressed from South Greenland up to Northwest Greenland by 2005 (Khan et al., 2010). Observations from meteorological stations at the U.S. Thule Air Force Base, remote sensing platforms, and climate reanalyses indicate a 3.5C mean annual warming in the Thule region and a 44% decrease in summer (JJAS) sea-ice concentrations in Baffin Bay from 1980-2010. Mean annual precipitation near Thule increased by 12% over this interval, with the majority of the increase occurring in fall (SON). To improve projections of future ice loss and sea-level rise in a warming climate, we are currently developing multi-proxy records (lake sediment cores, ice cores, glacial geologic data, glaciological models) of Holocene climate variability and cryospheric response in NW Greenland, with a focus on past warm periods. As part of our efforts to develop a millennial-length ice core paleoclimate record from the Thule region, we collected and analyzed snow pit samples and short firn cores (up to 20 m) from the coastal region of the GIS (2Barrel site; 76.9317 N, 63.1467 W) and the summit of North Ice Cap (76.938 N, 67.671 W) in 2011 and 2012, respectively. The 2Barrel ice core was sampled using a continuous ice core melting system at Dartmouth, and subsequently analyzed for major anion and trace element concentrations and stable water isotope ratios. Here we show that the 2Barrel ice core spanning 1990-2010 records a 25% increase in mean annual snow accumulation, and is positively correlated (r = 0.52, p<0.01) with ERA-Interim precipitation. The 2Barrel annual sea-salt Na concentration is strongly correlated (r = 0.5-0.8, p<0.05) with summer and fall sea-ice concentrations in northern Baffin Bay near Thule (Figure 1). We hypothesize that the positive correlation represents a significant Na contribution from frost flowers growing on fall frazil ice. Ongoing analyses will evaluate the relationship between MSA concentrations and sea ice extent. Our results show that a deep ice core collected from this dynamic and climate-sensitive region of NW Greenland would produce a valuable record of late Holocene climate and sea ice extent.

The projected demise of Barnes Ice Cap: Evidence of an unusually warm 21st century Arctic

NASA Astrophysics Data System (ADS)

Gilbert, A.; Flowers, G. E.; Miller, G. H.; Refsnider, K. A.; Young, N. E.; Radić, V.

2017-03-01

As a remnant of the Laurentide Ice Sheet, Barnes Ice Cap owes its existence and present form in part to the climate of the last glacial period. The ice cap has been sustained in the present interglacial climate by its own topography through the mass balance-elevation feedback. A coupled mass balance and ice-flow model, forced by Coupled Model Intercomparison Project Phase 5 climate model output, projects that the current ice cap will likely disappear in the next 300 years. For greenhouse gas Representative Concentration Pathways of +2.6 to +8.5 Wm-2, the projected ice-cap survival times range from 150 to 530 years. Measured concentrations of cosmogenic radionuclides 10Be, 26Al, and 14C at sites exposed near the ice-cap margin suggest the pending disappearance of Barnes Ice Cap is very unusual in the last million years. The data and models together point to an exceptionally warm 21st century Arctic climate.

Polar Ice Caps: a Canary for the Greenland Ice Sheet

NASA Astrophysics Data System (ADS)

Honsaker, W.; Lowell, T. V.; Sagredo, E.; Kelly, M. A.; Hall, B. L.

2010-12-01

Ice caps are glacier masses that are highly sensitive to climate change. Because of their hypsometry they can have a binary state. When relatively slight changes in the equilibrium line altitude (ELA) either intersect or rise above the land the ice can become established or disappear. Thus these upland ice masses have a fast response time. Here we consider a way to extract the ELA signal from independent ice caps adjacent to the Greenland Ice Sheet margin. It may be that these ice caps are sensitive trackers of climate change that also impact the ice sheet margin. One example is the Istorvet Ice Cap located in Liverpool Land, East Greenland (70.881°N, 22.156°W). The ice cap topography and the underlying bedrock surface dips to the north, with peak elevation of the current ice ranging in elevation from 1050 to 745 m.a.s.l. On the eastern side of the ice mass the outlet glaciers extending down to sea level. The western margin has several small lobes in topographic depressions, with the margin reaching down to 300 m.a.s.l. Topographic highs separate the ice cap into at least 5 main catchments, each having a pair of outlet lobes toward either side of the ice cap. Because of the regional bedrock slope each catchment has its own elevation range. Therefore, as the ELA changes it is possible for some catchments of the ice cap to experience positive mass balance while others have a negative balance. Based on weather observations we estimate the present day ELA to be ~1000 m.a.s.l, meaning mass balance is negative for the majority of the ice cap. By tracking glacier presence/absence in these different catchments, we can reconstruct small changes in the ELA. Another example is the High Ice Cap (informal name) in Milne Land (70.903°N, 25.626°W, 1080 m), East Greenland. Here at least 4 unconformities in ice layers found near the southern margin of the ice cap record changing intervals of accumulation and ablation. Therefore, this location may also be sensitive to slight changes in ELA where you can track an “on-off” type of mass balance switch. To place these ELA changes into temporal context, we propose to investigate proglacial lake environments below the various catchments. We intend to take rock flour as an indicator that the individual catchment is above the ELA. By contrasting the chronology from different catchments we can assemble minor ELA changes. Such an approach could be applied for other ice caps in Greenland and other areas, such as the Quelccaya Ice Cap, Peru.

Sensitivity, stability and future evolution of the world's northernmost ice cap, Hans Tausen Iskappe (Greenland)

NASA Astrophysics Data System (ADS)

Zekollari, Harry; Huybrechts, Philippe; Noël, Brice; van de Berg, Willem Jan; van den Broeke, Michiel R.

2017-03-01

In this study the dynamics and sensitivity of Hans Tausen Iskappe (western Peary Land, Greenland) to climatic forcing is investigated with a coupled ice flow-mass balance model. The surface mass balance (SMB) is calculated from a precipitation field obtained from the Regional Atmospheric Climate Model (RACMO2.3), while runoff is calculated from a positive-degree-day runoff-retention model. For the ice flow a 3-D higher-order thermomechanical model is used, which is run at a 250 m resolution. A higher-order solution is needed to accurately represent the ice flow in the outlet glaciers. Under 1961-1990 climatic conditions a steady-state ice cap is obtained that is overall similar in geometry to the present-day ice cap. Ice thickness, temperature and flow velocity in the interior agree well with observations. For the outlet glaciers a reasonable agreement with temperature and ice thickness measurements can be obtained with an additional heat source related to infiltrating meltwater. The simulations indicate that the SMB-elevation feedback has a major effect on the ice cap response time and stability. This causes the southern part of the ice cap to be extremely sensitive to a change in climatic conditions and leads to thresholds in the ice cap evolution. Under constant 2005-2014 climatic conditions the entire southern part of the ice cap cannot be sustained, and the ice cap loses about 80 % of its present-day volume. The projected loss of surrounding permanent sea ice and resultant precipitation increase may attenuate the future mass loss but will be insufficient to preserve the present-day ice cap for most scenarios. In a warmer and wetter climate the ice margin will retreat, while the interior is projected to thicken, leading to a steeper ice cap, in line with the present-day observed trends. For intermediate- (+4 °C) and high- warming scenarios (+8 °C) the ice cap is projected to disappear around AD 2400 and 2200 respectively, almost independent of the projected precipitation regime and the simulated present-day geometry.

Present-day dynamics and future evolution of the world's northernmost ice cap, Hans Tausen Iskappe (Greenland)

NASA Astrophysics Data System (ADS)

Zekollari, Harry; Huybrechts, Philippe; Noël, Brice; van de Berg, Willem Jan; van den Broeke, Michiel R.

2017-04-01

In this study the dynamics of Hans Tausen Iskappe (western Peary Land, Greenland) are investigated with a coupled ice flow - mass balance model. Precipitation is obtained from the Regional Climate Model RACMO 2.3 and the surface mass balance is calculated from a Positive Degree-Day runoff/retention model, for which the input parameters are derived from field observations. For the ice flow a 3-D higher-order thermo-mechanical model is used, which is run at a 250 m resolution. Under 1961-1990 climatic conditions a steady state ice cap is obtained that is overall similar in geometry to the present-day ice cap. Ice thickness, temperature and flow velocity in the interior agree well with observations. For the outlet glaciers a reasonable agreement with temperature and ice thickness measurements can only be obtained with an additional heat source related to infiltrating meltwater. The simulations indicate that the SMB-elevation feedback has a major effect on the ice cap response time and stability. This causes the southern part of the ice cap to be extremely sensitive to a change in climatic conditions and leads to thresholds in the ice cap evolution. Under constant 2005-2014 climatic conditions the entire southern part of the ice cap cannot be sustained and the ice cap loses about 80% of its present-day volume. The future projected loss of surrounding permanent sea-ice and corresponding potential sharp precipitation increase may however lead to an attenuation of the retreat and even potential stabilization of the ice cap for a warming of up to 2-3°C. In a warmer and wetter climate the ice margin will retreat while the interior is projected to grow, leading to a steeper ice cap, in line with the present-day observed trends. For intermediate (+4°C) and high warming scenarios (+8°C) the ice cap is projected to disappear respectively around 2400 and 2200 A.D., almost irrespective of the projected precipitation regime and the simulated present-day geometry.

The Size of Mars' Fluid Core From Mars k2 Love Number Obtained From Analysis of MGS Doppler Tracking.

NASA Astrophysics Data System (ADS)

Yoder, C. F.; Konopliv, A. S.; Yuan, D. N.; Standish, E. M.; Folkner, W. M.

2002-12-01

The solar tidal deformation of Mars, measured by its k2 potential Love number, has been obtained from analysis of MGS radio tracking. The observed k2 =0.164+-0.016 is large enough to rule out a solid iron core. The inferred core radius Rc (1600km

Present and Future Surface Mass Budget of Small Arctic Ice Caps in a High Resolution Regional Climate Model

NASA Astrophysics Data System (ADS)

Mottram, Ruth; Langen, Peter; Koldtoft, Iben; Midefelt, Linnea; Hesselbjerg Christensen, Jens

2016-04-01

Globally, small ice caps and glaciers make a substantial contribution to sea level rise; this is also true in the Arctic. Around Greenland small ice caps are surprisingly important to the total mass balance from the island as their marginal coastal position means they receive a large amount of precipitation and also experience high surface melt rates. Since small ice caps and glaciers have had a disproportionate number of long-term monitoring and observational schemes in the Arctic, likely due to their relative accessibility, they can also be a valuable source of data. However, in climate models the surface mass balance contributions are often not distinguished from the main ice sheet and the presence of high relief topography is difficult to capture in coarse resolution climate models. At the same time, the diminutive size of marginal ice masses in comparison to the ice sheet makes modelling their ice dynamics difficult. Using observational data from the Devon Ice Cap in Arctic Canada and the Renland Ice Cap in Eastern Greenland, we assess the success of a very high resolution (~5km) regional climate model, HIRHAM5 in capturing the surface mass balance (SMB) of these small ice caps. The model is forced with ERA-Interim and we compare observed mean SMB and the interannual variability to assess model performance. The steep gradient in topography around Renland is challenging for climate models and additional statistical corrections are required to fit the calculated surface mass balance to the high relief topography. Results from a modelling experiment at Renland Ice Cap shows that this technique produces a better fit between modelled and observed surface topography. We apply this statistical relationship to modelled SMB on the Devon Ice Cap and use the long time series of observations from this glacier to evaluate the model and the smoothed SMB. Measured SMB values from a number of other small ice caps including Mittivakkat and A.P. Olsen ice cap are also compared with model output. Finally we use climate simulations forced with two different RCP scenarios to examine the likely future evolution of SMB over these small ice masses.

New Zealand Maritime Glaciation: Millennial-Scale Southern Climate Change Since 3.9 Ma

NASA Astrophysics Data System (ADS)

Carter, Robert M.; Gammon, Paul

2004-06-01

Ocean Drilling Program Site 1119 is ideally located to intercept discharges of sediment from the mid-latitude glaciers of the New Zealand Southern Alps. The natural gamma ray signal from the site's sediment core contains a history of the South Island mountain ice cap since 3.9 million years ago (Ma). The younger record, to 0.37 Ma, resembles the climatic history of Antarctica as manifested by the Vostok ice core. Beyond, and back to the late Pliocene, the record may serve as a proxy for both mid-latitude and Antarctic polar plateau air temperature. The gamma ray signal, which is atmospheric, also resembles the ocean climate history represented by oxygen isotope time series.

Atmospheric Depositions of Natural and Anthropogenic Aerosols on the Guliya Ice Cap (Northwestern Tibetan Plateau) during the last 340 years

NASA Astrophysics Data System (ADS)

Sierra Hernandez, R.; Gabrielli, P.; Beaudon, E.; Thompson, L. G.; Wegner, A.

2017-12-01

Anthropogenic emissions (e.g., greenhouse gases, trace elements (TE) including toxic metals) to the atmosphere have dramatically increased since the Industrial Revolution in the 19th century. High temperature processes such as fossil fuel combustion and pyrometallurgy generate fumes and fine particles (< 0.1µm - 10 µm) containing toxic metals (e.g., Cd, Zn, Pb) that if not captured by emission controls can be transported over long distances by air masses and subsequently deposited far from their emission sources. Atmospheric TE monitoring programs, along with emission inventories, have been conducted in recent decades. However, they lack pre-1900 information which is necessary to contextualize current atmospheric changes. Thus, it is necessary to use natural archives (e.g., ice cores, lake sediments) to reconstruct atmospheric pollution trends. Glaciers and ice sheets preserve atmospheric species that are deposited as snow accumulates over time, creating valuable records of past climatic/environmental conditions. Polar ice cores have been used to obtain TE records. However, only a few non-polar ice core records provide continuous information back to pre-industrial times. Thus, ice core records of TEs from mid- and low-latitudes are needed to assess the spatial and temporal extent and levels of pollution in the environment. Here we present records of 29 TEs spanning the period 1650-1991 CE from the Guliya ice cap in the western Kunlun Mountains, northwest Tibetan Plateau to assess their natural and anthropogenic sources. The Guliya TEs records show two distinct periods with only crustal contributions prior to the 1850s and non-crustal contributions (Pb, Cd, Sb, Zn, Sn) after the 1850s. Enrichments of Pb, Cd, Sb, and Zn in Guliya between 1850 and 1950 can be attributed primarily to coal combustion emissions from western countries (Europe) while regional emissions (fossil fuel combustion, mining/smelting, fertilizers) from Central Asia, and probably from Kashgar in western China, and South Asia (India, Nepal) could be the source of the TE enrichments (Cd, Pb, Sn) observed in Guliya after 1950. This information can be used by modelers to assess pollution transport at local, regional, and global scales and by policy makers to develop strategies and policies to reduce their emissions.

Nature and History of Cenozoic Polar Ice Covers: The Case of the Greenland Ice Sheet

NASA Astrophysics Data System (ADS)

Spielhagen, R.; Thiede, J.

2009-04-01

The nature of the modern climate System is characterized by steep temperature gradients between the tropical and polar climatic zones and finds its most spectacular expression in the formation of ice caps in high Northern and Southern latitudes. While polar regions of Planet Earth have been glaciated repeatedly in the long course of their geological history, the Cenozoic transition from a „greenhouse" to an „icehouse" has in fact produced a unique climatic scenario with bipolar glacation, different from all previous glacial events. The Greenland ice sheet is a remainder of the Northern Hemisphere last glacial maximum ice sheets and represents hence a spectacular anomaly. Geological records from Tertiary and Quaternary terrestrial and oceanic sections have documented the presence of ice caps and sea ice covers both on the Southern as well on the Northern hemisphere since Eocene times, aqpprox. 45 Mio. years ago. While this was well known in the case of Antarctica already for some time, previous ideas about the origin of Northern hemisphere glaciation during Pliocene times (approx. 2-3 Mio. years ago) have been superceded by the dramatic findings of coarse, terrigenous ice rafted detritus in Eocene sediments from Lomonosov Ridge (close to the North Pole) apparently slightly older than the oldest Antarctic records of ice rafting.The histories of the onset of Cenozoic glaciation in high Northern and Southern latitudes remain enigmatic and are presently subjects of international geological drilling projects, with prospects to reveal some of their secrets over the coming decades. By virtue of the physical porperties of ice and the processes controlling the dynamics of the turn-over of the ice-sheets only young records of glacial ice caps on Antarctica and on Greemnland have been preserved, on Greenland with ice probably not older than a few hundred thousand years, on Antarctica potentially as old as 1.5-2 Mio. years. Deep-sea cores with their records od ice-rafting from off NE Greenland, Fram Strait and to the South of Greenland suggest the more or less continous existence of the Greenland ice sheet for the past 18 Mio. years, if not more, a phantastic supplement of the Northern hemisphere glaciation deduced from the ice cores. The dramatic decrease of extent and thickness of the Arctic sea ice cover of the past decades has aroused much public and political interest because of the potentially dramatic consequences for the exploitation of living and non-living resources as well as the socio-economic, technical and commercial systems developed in the Arctic seas and in the permafrost-infested adjacent land areas. The fate of the Greenland ice sheet with its impact on global sea level changes is one of the central unresolved problems. We urgently need novel marine research platforms which allow for an all-season presence of research and monitoring programs as well of scientific drilling programs in the Arctic Ocean.

Pre-industrial and recent (1970-2010) atmospheric deposition of sulfate and mercury in snow on southern Baffin Island, Arctic Canada.

PubMed

Zdanowicz, Christian; Kruemmel, Eva; Lean, David; Poulain, Alexandre; Kinnard, Christophe; Yumvihoze, Emmanuel; Chen, JiuBin; Hintelmann, Holger

2015-03-15

Sulfate (SO4(2-)) and mercury (Hg) are airborne pollutants transported to the Arctic where they can affect properties of the atmosphere and the health of marine or terrestrial ecosystems. Detecting trends in Arctic Hg pollution is challenging because of the short period of direct observations, particularly of actual deposition. Here, we present an updated proxy record of atmospheric SO4(2-) and a new 40-year record of total Hg (THg) and monomethyl Hg (MeHg) deposition developed from a firn core (P2010) drilled from Penny Ice Cap, Baffin Island, Canada. The updated P2010 record shows stable mean SO4(2-) levels over the past 40 years, which is inconsistent with observations of declining atmospheric SO4(2-) or snow acidity in the Arctic during the same period. A sharp THg enhancement in the P2010 core ca 1991 is tentatively attributed to the fallout from the eruption of the Icelandic volcano Hekla. Although MeHg accumulation on Penny Ice Cap had remained constant since 1970, THg accumulation increased after the 1980s. This increase is not easily explained by changes in snow accumulation, marine aerosol inputs or air mass trajectories; however, a causal link may exist with the declining sea-ice cover conditions in the Baffin Bay sector. The ratio of THg accumulation between pre-industrial times (reconstructed from archived ice cores) and the modern industrial era is estimated at between 4- and 16-fold, which is consistent with estimates from Arctic lake sediment cores. The new P2010 THg record is the first of its kind developed from the Baffin Island region of the eastern Canadian Arctic and one of very few such records presently available in the Arctic. As such, it may help to bridge the knowledge gap linking direct observation of gaseous Hg in the Arctic atmosphere and actual net deposition and accumulation in various terrestrial media. Copyright © 2014 Elsevier B.V. All rights reserved.

Devon Ice cap's future: results from climate and ice dynamics modelling via surface mass balance modelling

NASA Astrophysics Data System (ADS)

Rodehacke, C. B.; Mottram, R.; Boberg, F.

2017-12-01

The Devon Ice Cap is an example of a relatively well monitored small ice cap in the Canadian Arctic. Close to Greenland, it shows a similar surface mass balance signal to glaciers in western Greenland. Here we various boundary conditions, ranging from ERA-Interim reanalysis data via global climate model high resolution (5km) output from the regional climate model HIRHAM5, to determine the surface mass balance of the Devon ice cap. These SMB estimates are used to drive the PISM glacier model in order to model the present day and future prospects of this small Arctic ice cap. Observational data from the Devon Ice Cap in Arctic Canada is used to evaluate the surface mass balance (SMB) data output from the HIRHAM5 model for simulations forced with the ERA-Interim climate reanalysis data and the historical emissions scenario run by the EC-Earth global climate model. The RCP8.5 scenario simulated by EC-Earth is also downscaled by HIRHAM5 and this output is used to force the PISM model to simulate the likely future evolution of the Devon Ice Cap under a warming climate. We find that the Devon Ice Cap is likely to continue its present day retreat, though in the future increased precipitation partly offsets the enhanced melt rates caused by climate change.

The future of the Devon Ice cap: results from climate and ice dynamics modelling

NASA Astrophysics Data System (ADS)

Mottram, Ruth; Rodehacke, Christian; Boberg, Fredrik

2017-04-01

The Devon Ice Cap is an example of a relatively well monitored small ice cap in the Canadian Arctic. Close to Greenland, it shows a similar surface mass balance signal to glaciers in western Greenland. Here we use high resolution (5km) simulations from HIRHAM5 to drive the PISM glacier model in order to model the present day and future prospects of this small Arctic ice cap. Observational data from the Devon Ice Cap in Arctic Canada is used to evaluate the surface mass balance (SMB) data output from the HIRHAM5 model for simulations forced with the ERA-Interim climate reanalysis data and the historical emissions scenario run by the EC-Earth global climate model. The RCP8.5 scenario simulated by EC-Earth is also downscaled by HIRHAM5 and this output is used to force the PISM model to simulate the likely future evolution of the Devon Ice Cap under a warming climate. We find that the Devon Ice Cap is likely to continue its present day retreat, though in the future increased precipitation partly offsets the enhanced melt rates caused by climate change.

Perennial water ice identified in the south polar cap of Mars

NASA Astrophysics Data System (ADS)

Bibring, Jean-Pierre; Langevin, Yves; Poulet, François; Gendrin, Aline; Gondet, Brigitte; Berthé, Michel; Soufflot, Alain; Drossart, Pierre; Combes, Michel; Bellucci, Giancarlo; Moroz, Vassili; Mangold, Nicolas; Schmitt, Bernard; OMEGA Team; Erard, S.; Forni, O.; Manaud, N.; Poulleau, G.; Encrenaz, T.; Fouchet, T.; Melchiorri, R.; Altieri, F.; Formisano, V.; Bonello, G.; Fonti, S.; Capaccioni, F.; Cerroni, P.; Coradini, A.; Kottsov, V.; Ignatiev, N.; Titov, D.; Zasova, L.; Pinet, P.; Sotin, C.; Hauber, E.; Hoffman, H.; Jaumann, R.; Keller, U.; Arvidson, R.; Mustard, J.; Duxbury, T.; Forget, F.

2004-04-01

The inventory of water and carbon dioxide reservoirs on Mars are important clues for understanding the geological, climatic and potentially exobiological evolution of the planet. From the early mapping observation of the permanent ice caps on the martian poles, the northern cap was believed to be mainly composed of water ice, whereas the southern cap was thought to be constituted of carbon dioxide ice. However, recent missions (NASA missions Mars Global Surveyor and Odyssey) have revealed surface structures, altimetry profiles, underlying buried hydrogen, and temperatures of the south polar regions that are thermodynamically consistent with a mixture of surface water ice and carbon dioxide. Here we present the first direct identification and mapping of both carbon dioxide and water ice in the martian high southern latitudes, at a resolution of 2km, during the local summer, when the extent of the polar ice is at its minimum. We observe that this south polar cap contains perennial water ice in extended areas: as a small admixture to carbon dioxide in the bright regions; associated with dust, without carbon dioxide, at the edges of this bright cap; and, unexpectedly, in large areas tens of kilometres away from the bright cap.

Interannual observations and quantification of summertime H2O ice deposition on the Martian CO2 ice south polar cap

USGS Publications Warehouse

Brown, Adrian J.; Piqueux, Sylvain; Titus, Timothy N.

2014-01-01

The spectral signature of water ice was observed on Martian south polar cap in 2004 by the Observatoire pour l'Mineralogie, l'Eau les Glaces et l'Activite (OMEGA) ( Bibring et al., 2004). Three years later, the OMEGA instrument was used to discover water ice deposited during southern summer on the polar cap ( Langevin et al., 2007). However, temporal and spatial variations of these water ice signatures have remained unexplored, and the origins of these water deposits remains an important scientific question. To investigate this question, we have used observations from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument on the Mars Reconnaissance Orbiter (MRO) spacecraft of the southern cap during austral summer over four Martian years to search for variations in the amount of water ice. We report below that for each year we have observed the cap, the magnitude of the H2O ice signature on the southern cap has risen steadily throughout summer, particularly on the west end of the cap. The spatial extent of deposition is in disagreement with the current best simulations of deposition of water ice on the south polar cap (Montmessin et al., 2007). This increase in water ice signatures is most likely caused by deposition of atmospheric H2O ice and a set of unusual conditions makes the quantification of this transport flux using CRISM close to ideal. We calculate a ‘minimum apparent‘ amount of deposition corresponding to a thin H2O ice layer of 0.2 mm (with 70% porosity). This amount of H2O ice deposition is 0.6–6% of the total Martian atmospheric water budget. We compare our ‘minimum apparent’ quantification with previous estimates. This deposition process may also have implications for the formation and stability of the southern CO2 ice cap, and therefore play a significant role in the climate budget of modern day Mars.

Southwest Greenland's Alpine Glacier History: Recent Glacier Change in the Context of the Holocene Geologic Record

NASA Astrophysics Data System (ADS)

Larocca, L. J.; Axford, Y.; Lasher, G. E.; Lee, C. W.

2017-12-01

Due to anthropogenic climate change, the Arctic region is currently undergoing major transformation, and is expected to continue warming much faster than the global average. To put recent and future changes into context, a longer-term understanding of this region's past response to natural climate variability is needed. Given their sensitivity to modest climate change, small alpine glaciers and ice caps on Greenland's coastal margin (beyond the Greenland Ice Sheet) represent ideal features to record climate variability through the Holocene. Here we investigate the Holocene history of a small ( 160 square km) ice cap and adjacent alpine glaciers, located in southwest Greenland approximately 50 km south of Nuuk. We employ measurements on sediment cores from a glacier-fed lake in combination with geospatial analysis of satellite images spanning the past several decades. Sedimentary indicators of sediment source and thus glacial activity, including organic matter abundance, inferred chlorophyll-a content, sediment major element abundances, grain size, and magnetic susceptibility are presented from cores collected from a distal glacier-fed lake (informally referred to here as Per's Lake) in the summer of 2015. These parameters reflect changes in the amount and character of inorganic detrital input into the lake, which may be linked to the size of the upstream glaciers and ice cap and allow us to reconstruct their status through the Holocene. Additionally, we present a complementary record of recent changes in Equilibrium Line Altitude (ELA) for the upstream alpine glaciers. Modern ELAs are inferred using the accumulation area ratio (AAR) method in ArcGIS via Landsat and Worldview-2 satellite imagery, along with elevation data obtained from digital elevation models (DEMs). Paleo-ELAs are inferred from the positions of moraines and trim lines marking the glaciers' most recent expanded state, which we attribute to the Little Ice Age (LIA). This approach will allow us to explore the possibility of quantitatively or qualitatively linking changes in ELA (and thus the size of upstream glaciers) to specific sediment parameters. Ultimately, we aim to reconstruct glacier variability through the entire Holocene epoch, and to compare this history with 20th and 21st Century changes.

An East Siberian ice shelf during the Late Pleistocene glaciations: Numerical reconstructions

NASA Astrophysics Data System (ADS)

Colleoni, Florence; Kirchner, Nina; Niessen, Frank; Quiquet, Aurélien; Liakka, Johan

2016-09-01

A recent data campaign in the East Siberian Sea has revealed evidence of grounded and floating ice dynamics in regions of up to 1000 m water depth, and which are attributed to glaciations older than the Last Glacial Maximum (21 kyrs BP). The main hypothesis based on this evidence is that a small ice cap developed over Beringia and expanded over the East Siberian continental margin during some of the Late Pleistocene glaciations. Other similar evidence of ice dynamics that have been previously collected on the shallow continental shelves of the Arctic Ocean have been attributed to the penultimate glaciation, i.e. Marine Isotopes Stage 6 (≈140 kyrs BP). We use an ice sheet model, forced by two previously simulated MIS 6 glacial maximum climates, to carry out a series of sensitivity experiments testing the impact of dynamics and mass-balance related parameters on the geometry of the East Siberian ice cap and ice shelf. Results show that the ice cap developing over Beringia connects to the Eurasian ice sheet in all simulations and that its volume ranges between 6 and 14 m SLE, depending on the climate forcing. This ice cap generates an ice shelf of dimensions comparable with or larger than the present-day Ross ice shelf in West Antarctica. Although the ice shelf extent strongly depends on the ice flux through the grounding line, it is particularly sensitive to the choice of the calving and basal melting parameters. Finally, inhibiting a merging of the Beringia ice cap with the Eurasian ice sheet affects the expansion of the ice shelf only in the simulations where the ice cap fluxes are not large enough to compensate for the fluxes coming from the Eurasian ice sheet.

Forward Modeling of Oxygen Isotope Variability in Tropical Andean Ice Cores

NASA Astrophysics Data System (ADS)

Vuille, M. F.; Hurley, J. V.; Hardy, D. R.

2016-12-01

Ice core records from the tropical Andes serve as important archives of past tropical Pacific SST variability and changes in monsoon intensity upstream over the Amazon basin. Yet the interpretation of the oxygen isotopic signal in these ice cores remains controversial. Based on 10 years of continuous on-site glaciologic, meteorologic and isotopic measurements at the summit of the world's largest tropical ice cap, Quelccaya, in southern Peru, we developed a process-based physical forward model (proxy system model), capable of simulating intraseasonal, seasonal and interannual variability in delta-18O as observed in snow pits and short cores. Our results highlight the importance of taking into account post-depositional effects (sublimation and isotopic enrichment) to properly simulate the seasonal cycle. Intraseasonal variability is underestimated in our model unless the effects of cold air incursions, triggering significant monsoonal snowfall and more negative delta-18O values, are included. A number of sensitivity test highlight the influence of changing boundary conditions on the final snow isotopic profile. Such tests also show that our model provides much more realistic data than applying direct model output of precipitation delta-18O from isotope-enabled climate models (SWING ensemble). The forward model was calibrated with and run under present-day conditions, but it can also be driven with past climate forcings to reconstruct paleo-monsoon variability and investigate the influence of changes in radiative forcings (solar, volcanic) on delta-18O variability in Andean snow. The model is transferable and may be used to render a paleoclimatic context at other ice core locations.

Rapid Collapse of the Vavilov Ice Cap, Russian High Arctic.

NASA Astrophysics Data System (ADS)

Willis, M. J.; Zheng, W.; Durkin, W. J., IV; Pritchard, M. E.; Ramage, J. M.; Dowdeswell, J. A.; Benham, T. J.; Glazovsky, A.; Macheret, Y.; Porter, C. C.

2016-12-01

Cold based ice caps and glaciers are thought to respond slowly to environmental changes. As sea ice cover evolves in the Arctic, a feedback process alters air-temperatures and precipitation patterns across the region. During the last decades of the 20th century the land-terminating western margin of the Vavilov Ice Cap, on October Revolution Island of the Severnaya Zemlya Archipelago, advanced slowly westwards. The advance was driven by precipitation changes that occurred about half a millennia ago. InSAR shows that in 1996 the margin sustained ice speeds of around 20 m/yr. By 2000 the ice front had moved a short distance into the Kara Sea and had transitioned to a marine-terminating front, although an ice apron around the ice margin indicates the ice there was still frozen to the bed and there is no evidence of calving in satellite imagery. In 2013 ice motions near the terminus had accelerated to around 1 m/day. By late 2015 the main trunk of the newly activated outlet glacier attained speeds of 25 m/day and the inland portion of the ice cap thinned at rates of more than 0.3 m/day. The acceleration of the outlet glacier occurred due to its advance over weak, water-saturated marine sediments that provide little resistance to ice flow, and to the removal of lateral resistive stresses as the glacier advanced out into an open embayment. Longitudinal stretching at the front forces an increase in the surface slope upstream. Rapid rates of motion inland generate frictional melt at the bed, possibly aided by cryohydrological warming. Large areas of the interior of the Vavilov ice cap are now below the equilibrium line and the grounded portion of the ice cap is losing mass at a rate of 4.5 km3 w.e./year. The changes at the Vavilov are likely irrecoverable in a warming climate due to a reduction in the accumulation area of the ice cap. Increased precipitation drove the advance, which accelerated due to the presence of soft sediments. The acceleration lowered the elevation of the interior portion of the ice cap to a point from which it cannot recover. A second, similar collapse seems to be underway at basin-2 on the southern margin of the Austfonna Ice cap in Svalbard.

Sunlight penetration through the Martian polar caps: Effects on the thermal and frost budgets

NASA Technical Reports Server (NTRS)

Lindner, Bernhard Lee

1992-01-01

An energy balance model of the seasonal polar caps on Mars is modified to include penetration of solar radiation into and through the ice. Penetration of solar radiation has no effect on subsurface temperature or total frost sublimation if seasonal ice overlies a dust surface. An effect is noted for seasonal ice which overlies the residual polar caps. For the case of an exposed water-ice residual polar cap, the temperature at depth is calculated to be up to several degrees warmer and the calculated lifetime of seasonal CO2 frost is slightly lower when penetration of sunlight is properly treated in the model. For the case of a residual polar cap which is perennially covered by CO2 frost, the calculated lifetime of seasonal CO2 frost is very slightly increased as a result of sunlight penetration through the ice. Hence, penetration of sunlight into the ice helps to stabilize the observed dichotomy in the residual polar caps on Mars, although it is a small effect.

Sunlight penetration through the Martian polar caps - Effects on the thermal and frost budgets

NASA Technical Reports Server (NTRS)

Lindner, Bernhard L.

1992-01-01

An energy balance model of the seasonal polar caps on Mars is modified to include penetration of solar radiation into and through the ice. Penetration of solar radiation has no effect on subsurface temperature or total frost sublimation if seasonal ice overlies a dust surface. An effect is noted for seasonal ice which overlies the residual polar caps. For the case of an exposed water-ice residual polar cap, the temperature at depth is calculated to be up to several degrees warmer, and the calculated lifetime of seasonal CO2 frost is slightly lower when penetration of sunlight is properly treated in the model. For the case of a residual polar cap which is perennially covered by CO2 frost, the calculated lifetime of seasonal CO2 frost is very slightly increased as a result of sunlight penetration through the ice. Hence, penetration of sunlight into the ice helps to stabilize the observed dichotomy in the residual polar caps on Mars, although it is a small effect.

Is CO2 ice permanent?

NASA Technical Reports Server (NTRS)

Lindner, Bernhard Lee

1992-01-01

Carbon dioxide ice has been inferred to exist at the south pole in summertime, but Earth based measurements in 1969 of water vapor in the Martian atmosphere suggest that all CO2 ice sublined from the southern polar cap and exposed underlying water ice. This implies that the observed summertime CO2 ice is of recent origin. It appears possible to construct an energy balance model that maintains seasonal CO2 ice at the south pole year round and still reasonably simulates the polar cap regression and atmospheric pressure data. This implies that the CO2 ice observed in the summertime south polar cap could be seasonal in origin, and that minor changes in climate could cause CO2 ice to completely vanish, as would appear to have happened in 1969. However, further research remains before it is certain whether the CO2 ice observed in the summertime south polar cap is seasonal or is part of a permanent reservoir.

Paleo ice-cap surfaces and extents

NASA Astrophysics Data System (ADS)

Gillespie, A.; Pieri, D.

2008-12-01

The distribution, equilibrium-line altitude (ELA) and timing of Pleistocene alpine glaciers are used to constrain paleoclimatic reconstructions. Attention has largely focused on the geomorphic evidence for the former presence of simple valley glaciers; paleo alpine ice caps and their outlet glaciers have proven to be more problematical. This is especially so in the remote continental interior of Asia, where the research invested in the Alps or Rocky Mountains has yet to be duplicated. Even the putative existence and size of paleo ice caps in Tibet and the Kyrgyz Tien Shan is controversial. Remote sensing offers the opportunity to assess vast tracts of land quickly, with images and co-registered digital elevation models (DEMs) offering the most information for studies of paleoglaciers. We pose several questions: (1) With what confidence can nunataks be identified remotely? (2) What insights do their physiographic characteristics offer? (3) What characteristics of the bed of a paleo ice cap can be used to identify its former presence remotely? and (4) Can the geomorphic signatures of the edges of paleo ice caps be recognized and mapped? Reconstruction of the top surface of a paleo ice cap depends on the recognition of nunataks, typically rougher at 1 m to 100 m scales than their surroundings. Nunataks in southern Siberia are commonly notched by multiple sub- horizontal bedrock terraces. These step terraces appear to originate from freeze-thaw action on the rock-ice interface during periods of stability, and presence of multiple terraces suggests stepwise lowering of ice surfaces during deglaciation. An older generation of step-terraced nunataks, distinguished by degraded and eroded terraces, delineates a larger paleo ice cap in the Sayan Range (Siberian - Mongolian border) that significantly pre-dates the last glacial maximum (LGM). Large ice caps can experience pressure melting at their base and can manifest ice streams within the ice cap. Valleys left behind differ from fluvial valleys in their width/depth profiles: the channels maintain width but get shallower near their sources. Link junction angle distributions within superimposed drainage networks are broader and distinct from those of evolved fluvial networks, and their character and statistics can be used to identify the perimeters of large paleo ice caps. (This work was carried out in part at the Jet Propulsion Laboratory of the California Institute of Technology under contract to NASA.)

Insight into the latitudinal distribution of methane emissions throughout the Holocene from ice core methane records.

NASA Astrophysics Data System (ADS)

Sowers, T. A.; Vladimirova, D.; Blunier, T.

2017-12-01

During the preAnthropogenic era (prior to 1600AD) the interpolar CH4 gradient (IPG) is effectively dictated by the ratio of tropical to Pan Arctic CH4 emissions. IPG records from ice cores in Greenland and Antarctica provide fundamental information for assessing the latitudinal distribution of CH4 emissions and their relation to global climate change. We recently constructed a high-resolution (100yr) record of IPG changes throughout the Holocene using the ReCAP (E. Greenland) and WAIS (W. Antarctica) ice cores. Contemporaneous samples from both cores were analyzed on the same day to minimize analytical uncertainties associated with IPG reconstructions. CH4results from the WAIS core were indistinguishable from previous results suggesting our analytical scheme was intact (± 3ppb). Our reconstructed IPG showed early Holocene IPG values of 65ppb declining throughout the Holocene to values approximating 45 ppb during the latest portion of the Holocene (preAnthropogenic). We then utilized an eight box atmospheric methane box model (EBAMM) to quantify emission scenarios that agree with ice core CH4 records (concentration, IPG and isotopic composition). Our results are consistent with the idea that early Holocene peatland development in the PanArctic regions followed glacier retreat near the end of the last glacial termination contributing an additional 20Tg of CH4/yr relative to the late Holocene. In addition, we had to invoke elevated biomass burning emissions (40Tg/yr) during the early Holocene to account for the elevated d13CH4 values.

A high resolution record of chlorine-36 nuclear-weapons-tests fallout from Central Asia

USGS Publications Warehouse

Green, J.R.; Cecil, L.D.; Synal, H.-A.; Santos, J.; Kreutz, K.J.; Wake, C.P.

2004-01-01

The Inilchek Glacier, located in the Tien Shan Mountains, central Asia, is unique among mid-latitude glaciers because of its relatively large average annual accumulation. In July 2000, two ice cores of 162 and 167 meters (m) in length were collected from the Inilchek Glacier for (chlorine-36) 36Cl analysis a part of a collaborative international effort to study the environmental changes archived in mid-latitude glaciers worldwide. The average annual precipitation at the collection site was calculated to be 1.6 m. In contrast, the reported average annual accumulations at the high-latitude Dye-3 glacial site, Greenland, the mid-latitude Guliya Ice Cap, China, and the mid-latitude Upper Fremont Glacier, Wyoming, USA, were 0.52, 0.16 and 0.76 m, respectively. The resolution of the 36Cl record in one of the Inilchek ice cores was from 2 to 10 times higher than the resolution of the records at these other sites and could provide an opportunity for detailed study of environmental changes that have occurred over the past 150 years. Despite the differences in accumulation among these various glacial sites, the 36Cl profile and peak concentrations for the Inilchek ice core were remarkably similar in shape and magnitude to those for ice cores from these other sites. The 36Cl peak concentration from 1958, the year during the mid-1900s nuclear-weapons-tests period when 36Cl fallout was largest, was preserved in the Inilchek core at a depth of 90.56 m below the surface of the glacier (74.14-m-depth water equivalent) at a concentration of 7.7 ?? 105 atoms of 36Cl/gram (g) of ice. Peak 36Cl concentrations from Dye-3, Guliya and the Upper Fremont glacial sites were 7.1 ?? 105, 5.4 ?? 105 and 0.7 ?? 105 atoms of 36Cl/g of ice, respectively. Measurements of 36Cl preserved in ice cores improve estimates of historical worldwide atmospheric deposition of this isotope and allow the sources of 36Cl in ground water to be better identified. ?? 2004 Published by Elsevier B.V.

Tibetan Glaciers as Integrators and Sentinels of Climate Change

NASA Astrophysics Data System (ADS)

Thompson, L. G.; Tandong, Y.; Davis, M. E.; Kehrwald, N. M.; Mosley-Thompson, E. S.

2008-12-01

Information from ice cores collected over the last two decades across the Tibetan Plateau demonstrates that this is a climatically diverse and complex region. Records spanning more than 500,000 years have been recovered from the Guliya ice cap in the far northwestern Kunlun Mountains, where the climate is dominated by the westerly flow over the Eurasian land mass. Shorter records (less than 10,000 years) have been recovered from ice fields in the central Himalaya to the south, where a monsoonal climate regime dominates and the annual accumulation is high. On decadal and longer timescales IPCC climate models predict that continued anthropogenic greenhouse gas emissions will force air temperature to increase faster at higher elevations. This vertical amplification will be greatest in low latitudes due to upper tropospheric humidity and water vapor feedback. Meteorological records across the Tibetan Plateau indicate that temperatures have risen since the mid-1950s and the rate of warming is greater (0.3°C per decade) at the higher elevation stations. Likewise, the stable isotopic compositions of ice cores across the Plateau show an overall the 20th Century enrichment that is greatest at the highest elevation sites. Glaciers in the central Himalayas, including many around the Tibetan Plateau, are experiencing an accelerating rate of ice loss, due in part to current temperature trends and associated feedbacks. Ice loss in the central Himalayas is evident from ice cores recovered in 2006 from the Naimona'nyi ice field. Unlike previous cores from glaciers around the world, including those drilled across the Tibetan Plateau, the Naimona'nyi cores lack the elevated levels of beta radioactivity from the decay of 36Cl and 3H associated with atmospheric thermonuclear bomb testing in the 1950s and 1960s. This suggests that net mass (ice) loss has exceeded accumulation on this glacier since at least 1950. If the climate conditions that govern the mass balance on Naimona'nyi extend to other glaciers in the region, the implications for future water resources in South Asia could be dire as these glaciers feed the headwaters of the Indus, Ganges and Brahmaputra Rivers which sustain the world's most populous region.

Life Cores: A Sci-Art Collaboration Between a Snow/Ice Researcher, an Artist/Educator, Students, and Street Road Artists Space

NASA Astrophysics Data System (ADS)

Dooley, J.; Courville, Z.; Artinian, E.

2016-12-01

BackgroundStreet Road Artists Space Summer 2015 show was Sailing Stones. Works presented scenarios on tension between transience and permanence, highlighting cultural constructs imposed onto landscape and place. Dooley's installation, CryoZen Garden, operated as visual metaphor, modeling cryospheric processes and explored effects of melting polar ice caps on a warming world. A grant from Pennsylvania Partners in the Arts, with a focus on sharing contemporary works which were participatory, conceptual, and polar science research-based, allowed for a new project to engage community members, particularly students.MethodsIn this project students were introduced to the work of Dooley, artist/educator and Courville, snow/ice researcher. Students created `Life Cores', a take on ice and sediment coring scientists use as evidence of Earth's atmospheric and geologic changes. Students were given plastic tubes 2' long and 2" in diameter and were asked to add a daily layer of materials taken from everyday life, for a one month period. Students chose materials important to them personally, and kept journals, reflecting on items' significance, and/or relationship to life and world events. After creation of the Life Cores, Courville and Dooley visited students, shared their work on polar research, what it's like to live and work on ice, and ways science and art can intertwine to create better understanding of climate change issues. Students used core logging sheets to make observations of each others' life cores, noting layer colors, textures and deposition rates as some of the characteristics researchers use in ice and sediment core interpretation. Students' work was exhibited at Street Road and will remain on Street Road's website. Courville and Dooley presented to the general public during the opening. ConclusionsParticipants were better able to answer the question, How do we know what we know from coring? by relating the science to something that is known and personal, such as the passage of time with recognizable indicators. Success of the project was based on attendance, very positive feedback from participants, subsequent visits and the effects this programming had on continued efforts to forge long-term relationships with community groups.

Long-term evolution of a small ice cap in Greenland: a dynamic perspective from numerical flow modelling

NASA Astrophysics Data System (ADS)

Vieli, Andreas; Lane, Timothy; Adamson, Kathryn

2017-04-01

Small ice caps at the periphery of the Greenland ice sheet are often close to the limit of existence and are therefore expected to respond more sensitively to climate change than the land-margin of the neighboring ice sheet. However, their past evolution and dynamic behavior is poorly understood and their use as climate indicators therefore remains so far limited. We here aim to provide a long-term dynamic reconstruction of Lyngmarksbraeen, a small (32km2) ice cap on Disko Island in West Greenland, with a particular focus on the little ice age (LIA, since 1200AD). We use a 2-dim. time-dependent numerical flow model (SIA) and a PDD-mass balance model in combination with historical observations, geomorphological mapping and exposure dating to simulate its long-term evolution and dynamic behaviour. We specifically focus on retreat since the LIA, which is well constrained by geomorphological evidence and historical maps and length records of several small outlet glaciers and data from local and regional climate stations (Qeqertarssuaq and Ilulisat). We also explore aspects related to flow dynamics and find that the dynamic state of this ice cap is, at any time, far from being balanced and is highly sensitive to the surface elevation mass balance feedback and results in an asynchronous response of the different outlets and hysteresis-type behaviour. The modelling is able to reproduce the observed LIA-extent and the almost continuous retreat over the last hundred years well. It further indicates that the ice cap was already dynamically inert since the 1960s. Today, the ice cap has lost almost its entire accumulation area and even without any further warming in the future, the ice cap is expected to vanish within a couple of decades.

Variability of Mars' North Polar Water Ice Cap: I. Analysis of Mariner 9 and Viking Orbiter Imaging Data

USGS Publications Warehouse

Bass, Deborah S.; Herkenhoff, Kenneth; Paige, David A.

2000-01-01

Previous studies interpreted differences in ice coverage between Mariner 9 and Viking Orbiter observations of Mars' north residual polar cap as evidence of interannual variability of ice deposition on the cap. However, these investigators did not consider the possibility that there could be significant changes in the ice coverage within the northern residual cap over the course of the summer season. Our more comprehensive analysis of Mariner 9 and Viking Orbiter imaging data shows that the appearance of the residual cap does not show large-scale variance on an interannual basis. Rather we find evidence that regions that were dark at the beginning of summer look bright by the end of summer and that this seasonal variation of the cap repeats from year to year. Our results suggest that this brightening was due to the deposition of newly formed water ice on the surface. We find that newly formed ice deposits in the summer season have the same red-to-violet band image ratios as permanently bright deposits within the residual cap. We believe the newly formed ice accumulates in a continuous layer. To constrain the minimum amount of deposited ice, we used observed albedo data in conjunction with calculations using Mie theory for single scattering and a delta-Eddington approximation of radiative transfer for multiple scattering. The brightening could have been produced by a minimum of (1) a ~35-μm-thick layer of 50-μm-sized ice particles with 10% dust or (2) a ~14-μm-thick layer of 10-μm-sized ice particles with 50% dust.

Elevation Changes of Ice Caps in the Canadian Arctic Archipelago

NASA Technical Reports Server (NTRS)

Abdalati, W.; Krabill, W.; Frederick, E.; Manizade, S.; Martin, C.; Sonntag, J.; Swift, R.; Thomas, R.; Yungel, J.; Koerner, R.

2004-01-01

Precise repeat airborne laser surveys were conducted over the major ice caps in the Canadian Arctic Archipelago in the spring of 1995 and 2000 in order to measure elevation changes in the region. Our measurements reveal thinning at lower elevations (below 1600 m) on most of the ice caps and glaciers, but either very little change or thickening at higher elevations in the ice cap accumulation zones. Recent increases in precipitation in the area can account for the slight thickening where it was observed, but not for the thinning at lower elevations. For the northern ice caps on the Queen Elizabeth Islands, thinning was generally less than 0.5 m/yr , which is consistent with what would be expected from the warm temperature anomalies in the region for the 5-year period between surveys and appears to be a continuation of a trend that began in the mid 1980s. Further south, however, on the Barnes and Penny ice caps on Baffin Island, this thinning was much more pronounced at over 1 m/yr in the lower elevations. Here temperature anomalies were very small, and the thinning at low elevations far exceeds any associated enhanced ablation. The observations on Barnes, and perhaps Penny are consistent with the idea that the observed thinning is part of a much longer term deglaciation, as has been previously suggested for Barnes Ice Cap. Based on the regional relationships between elevation and elevation-change in our data, the 1995-2000 mass balance for the region is estimated to be 25 cu km/yr of ice, which corresponds to a sea level increase of 0.064 mm/ yr . This places it among the more significant sources of eustatic sea level rise, though not as substantial as Greenland ice sheet, Alaskan glaciers, or the Patagonian ice fields.

Tracing the hydrological cycle by water stable isotopes on the Tibetan plateau

NASA Astrophysics Data System (ADS)

Tian, L.; Yao, T.; Yu, W.

2013-05-01

A network of precipitation, river, lake water, ice core and atmospheric vapor sampling was set up on the Tibetan Plateau to trance the moisture origins supplied to the plateau, the inland hydrological cycle process and land surface evaporation processes. This work shows different moisture from Indian Ocean monsoon and the westerlies dominate the precipitation δ18O in the south and north of the plateau respectively, which can cause a difference in precipitation δ18O of about 5‰ in average. Precipitation δ18O bears "temperature effect" in the northern Tibetan Plateau, whereas the seasonal precipitation δ18O shows precipitation "amount effect" in the south. This relation is also held in the ice core records on the plateau. An instance is the δ18O record from shallow ice cores in Muztagata Glacier, Dunde ice cap and Naimona'Nyi Glacier. The ice core δ18O record from monsoon region in south Tibet, such as Dasuopu glacier in Xixiabangma, shows a precipitation "amount effect" at least in the annual scale. Further isotope enrichment can be found in the land surface evaporation processes. A simple case is in the close lake system in Yamdruk-tso catchment, southern part of Tibetan Plateau. Both observation and simulation work shows the enrichment of heavy isotope in lake water can be over 10‰ for δ18O, which is much linked to the local climatic condition. Simulation work also shows that atmospheric vapor isotope is also very important to capture the lake water δD value. However, vapor isotopes data are usually less available on the plateau.

Influence of aeolian activities on the distribution of microbial abundance in glacier ice

NASA Astrophysics Data System (ADS)

Chen, Y.; Li, X.-K.; Si, J.; Wu, G.-J.; Tian, L.-D.; Xiang, S.-R.

2014-10-01

Microorganisms are continuously blown onto the glacier snow, and thus the glacial depth profiles provide excellent archives of microbial communities and climatic and environmental changes. However, it is uncertain about how aeolian processes that cause climatic changes control the distribution of microorganisms in the glacier ice. In the present study, microbial density, stable isotopic ratios, 18O / 16O in the precipitation, and mineral particle concentrations along the glacial depth profiles were collected from ice cores from the Muztag Ata glacier and the Dunde ice cap. The ice core data showed that microbial abundance was often, but not always associated with high concentrations of particles. Results also revealed clear seasonal patterning with high microbial abundance occurring in both the cooling autumn and warming spring-summer seasons. Microbial comparisons among the neighbouring glaciers display a heterogeneous spatial pattern, with the highest microbial cell density in the glaciers lying adjacent to the central Asian deserts and lowest microbial density in the southwestern margin of the Tibetan Plateau. In conclusion, microbial data of the glaciers indicates the aeolian deposits of microorganisms in the glacier ice and that the spatial patterns of microorgansisms are related to differences in sources of microbial flux and intensity of aeolian activities in the current regions. The results strongly support our hypothesis of aeolian activities being the main agents controlling microbial load in the glacier ice.

Emergent Dead Vegetation and Paired Cosmogenic Isotope Constraints on Ice Cap Activity, Baffin Island, Arctic Canada

NASA Astrophysics Data System (ADS)

Pendleton, S.; Miller, G. H.

2014-12-01

Recent summer warming has now raised the equilibrium line above almost all ice caps on Baffin Island, resulting in surface lowering and marginal recession everywhere. As cold-based ice recedes it frequently exposes in situ tundra plants that were living at the time ice expanded across the site. Radiocarbon dates for each plant records when cold summers dropped regional snowline below the site, killing the plants, and snowline remained below the site until the collection date. The kill dates also represent the last time that the climate was warm enough to expose the sampling location. Seventy-six vegetation samples collected in 2013 from the Penny Ice Cap region have been dated, with significant age populations at ~0.5, 1.8, 2.3, and 3.6 ka. The absence of ages around ~1, 2, 3, 4.5, and 5.5 ka suggest periods of either no snowline depression or stability. Sixteen vegetation samples returned ages of >45 ka (2 revisited sites from 2010, 14 new). It is postulated that these radiocarbon dead samples were last exposed during the last interglaciation (~120 ka), the last time climate was as warm as present. In addition to plant collections, bedrock exposures at the ice margins were sampled for 26Al/10Be cosmogenic nuclide dating. Seven samples from and around the Penny Ice cap have returned maximum exposure ages from ~ 0.6-0.9 ma and total histories of ~0.6-1.5 ma. In general, samples from the larger Penny Ice Cap exhibited lower amounts of exposure (~20% of total history) than those samples from smaller, localized ice caps (~55%). Radiocarbon dead sites north of the Penny Ice cap experienced significantly more exposure over their lifetimes than their counterparts east of the Penny Ice cap, suggesting significant differences in local and regional land ice fluctuations over the last 2 million years. Utilizing both the method of in situ moss and 26Al/10Be dating provides new insight into both the recent activity and long-term evolution of ice on Baffin Island. In particular these new data help to shed light on how late Holocene coolings affect both large and small ice bodies and how this behavior is represented in the longer-term burial/exposure record contained within the rock surface.

Ice thickness measurements and volume estimates for glaciers in Norway

NASA Astrophysics Data System (ADS)

Andreassen, Liss M.; Huss, Matthias; Melvold, Kjetil; Elvehøy, Hallgeir; Winsvold, Solveig H.

2014-05-01

Whereas glacier areas in many mountain regions around the world now are well surveyed using optical satellite sensors and available in digital inventories, measurements of ice thickness are sparse in comparison and a global dataset does not exist. Since the 1980s ice thickness measurements have been carried out by ground penetrating radar on many glaciers in Norway, often as part of contract work for hydropower companies with the aim to calculate hydrological divides of ice caps. Measurements have been conducted on numerous glaciers, covering the largest ice caps as well as a few smaller mountain glaciers. However, so far no ice volume estimate for Norway has been derived from these measurements. Here, we give an overview of ice thickness measurements in Norway, and use a distributed model to interpolate and extrapolate the data to provide an ice volume estimate of all glaciers in Norway. We also compare the results to various volume-area/thickness-scaling approaches using values from the literature as well as scaling constants we obtained from ice thickness measurements in Norway. Glacier outlines from a Landsat-derived inventory from 1999-2006 together with a national digital elevation model were used as input data for the ice volume calculations. The inventory covers all glaciers in mainland Norway and consists of 2534 glaciers (3143 glacier units) covering an area of 2692 km2 ± 81 km2. To calculate the ice thickness distribution of glaciers in Norway we used a distributed model which estimates surface mass balance distribution, calculates the volumetric balance flux and converts it into thickness using the flow law for ice. We calibrated this model with ice thickness data for Norway, mainly by adjusting the mass balance gradient. Model results generally agree well with the measured values, however, larger deviations were found for some glaciers. The total ice volume of Norway was estimated to be 275 km3 ± 30 km3. From the ice thickness data set we selected glacier units or entire ice caps with sufficient data to interpolate mean ice thickness. Scaling constants c and γ were fitted by least square regression for totally 86 glacier units and 8 ice caps. The ice volume results from scaling were sensitive to how the glaciers are divided and scaling applied to glaciers divided into glacier units gave best results. Scaling laws for ice caps did not work well, as the mean thickness of the ice caps varies less than their areas and the sample of ice caps with sufficient measurement coverage was small. Calculated ice volumes range from 280 to 305 km3, much higher than values obtained from the literature (134-184 km3). As measurements are biased towards outlets from the largest and thickest ice caps, more measurements are needed for a better estimate of the present ice volume of the smaller glaciers.

The last forests in Greenland, and the age of the ice sheet

NASA Astrophysics Data System (ADS)

Funder, Svend; Schmidt, Astrid M. Z.; Dahl-Jensen, Dorthe; Steffensen, Jørgen Peder; Willerslev, Eske

2014-05-01

Recently ancient DNA (aDNA) studies of the basal ice in the Camp Century ice core, northern Greenland, have shown that mixed coniferous-deciduous forest grew here before the area was invaded and permanently covered by the ice sheet. The coring site is situated only 100 km from the present ice margin and more than 500 km from the ice divide, indicating that since this last inception the northern part of the ice sheet never receded more than 100 km from its present margin. Dating of the basal ice and obtaining an age for the forest and for the beginning of the ice sheet's permanency has been attempted by analyzing for optically stimulated luminescence (OSL), meteoric 10Be/36Cl cosmogenic nuclides, 234U/238U recoil. These methods all provide only minimum ages and show that the forest at Cap Century is older than 500 ka. Comparison with other Pleistocene "forest sites" in Greenland - the Kap København Formation in northernmost Greenland, the DYE-3 ice core in the south, the ODP boring 646 south of Greenland, as well as results from basal ice in the GRIP ice core - extends the minimum age to c. 1 ma. The maximum age is provided by the Kap København Formation, which must be older - or contemporaneous. The formation has recently been confirmed to date within the interval 2-2.5 ma, with a preferred age of 2.3-2.4 ma. Surprisingly, application of the molecular clock of insect COI sequences on the Camp Century aDNA now seem to push the minimum age just as far back - to 2.4 ma, suggesting that the timberline boreal forest at Kap København is contemporaneous with the mixed forest at Camp Century, 600 km to the south. From this we conclude that the northern ice sheet dome, which today contains 85% of the total ice sheet volume, has remained within 100 km of its present margin for at least 1 ma, and possibly may go back as far as 2.4 ma. The ice sheet has therefore survived both interglacials and "super interglacials" that were both warmer and longer than the present. This may give us some hope for the future.

The Climate and Human Impacts of Major Explosive Volcanism AD670-730, A Multi-proxy Assessment

NASA Astrophysics Data System (ADS)

Gao, C.; Ludlow, F.

2013-12-01

Chronologically secure volcanic events can provide an important tool to improve ice core dating as well as our understanding of volcano-climate responses. However, there is a substantial lack of reference horizons for ice-core dating during the first millennium, excepting the Taupo (New Zealand, AD186×10) and Vesuvius (Italy, AD 79) eruptions. In this exploratory case-study, we use a total of 20 ice core records, 9 from the Arctic and 11 from the Antarctic, together with historical records to examine the occurrence and climatic impact of explosive volcanism, AD 670-730. Sulfate signals comparable in magnitude to the sizeable 1815 Tambora eruption are detected in all of the ice-core time series, with different cores attributing the timing of eruptions to AD 676×2, 688×2, or 700×2, respectively. Historical records of widespread frost damage, anomalously warm winters, drought, famine and mortality from Chinese, European and Middle Eastern chronicles suggest substantial climate and social perturbations during AD 677-685 and AD 699-709. The distinctive double-peak feature seen in the majority of the volcanic signals from both poles at AD 676×2 and AD 688×2 suggests that these signals may belong to the same eruption, with those cores dating the signals to c.AD 676 generally considered to have a more precise chronology. Combining the evidence from natural and historical anthropogenic records and taking into account uncertainties (e.g. resolution, dating accuracy) associated with individual ice cores, we propose that a (most-likely) low-latitude eruption took place around AD676, followed by another possible eruption around AD700, identifiable by the significant acidity in polar ice-caps and historical documents. Unique historical observations of 'blood rain' in Ireland (often associated with Saharan sand deposition, but also plausibly with iron and manganese-rich tephra falls) also suggest a high-latitude eruption (possibly Icelandic) at AD693, corresponding to a GISP2 volcanic signal at 690.7×2.5. Results from this study attempt to characterize and reduce uncertainties in ice-core volcanic reconstructions, and make a contribution towards establishing a new reference horizon for this relatively under-studied period.

Ganymede G1 & G2 Encounters - Interior of Ganymede

NASA Image and Video Library

1997-12-16

NASA's Voyager images are used to create a global view of Ganymede. The cut-out reveals the interior structure of this icy moon. This structure consists of four layers based on measurements of Ganymede's gravity field and theoretical analyses using Ganymede's known mass, size and density. Ganymede's surface is rich in water ice and Voyager and Galileo images show features which are evidence of geological and tectonic disruption of the surface in the past. As with the Earth, these geological features reflect forces and processes deep within Ganymede's interior. Based on geochemical and geophysical models, scientists expected Ganymede's interior to either consist of: a) an undifferentiated mixture of rock and ice or b) a differentiated structure with a large lunar sized "core" of rock and possibly iron overlain by a deep layer of warm soft ice capped by a thin cold rigid ice crust. Galileo's measurement of Ganymede's gravity field during its first and second encounters with the huge moon have basically confirmed the differentiated model and allowed scientists to estimate the size of these layers more accurately. In addition the data strongly suggest that a dense metallic core exists at the center of the rock core. This metallic core suggests a greater degree of heating at sometime in Ganymede's past than had been proposed before and may be the source of Ganymede's magnetic field discovered by Galileo's space physics experiments. http://photojournal.jpl.nasa.gov/catalog/PIA00519

Change in the Extent of Baffin Island's Penny Ice Cap in Response to Regional Warming, 1969 - 2014

NASA Astrophysics Data System (ADS)

Cox, M. C.; Cormier, H. M.; Gardner, A. S.

2014-12-01

Glaciers are retreating globally in response to warmer atmospheric temperatures, adding large volumes of melt water to the world's oceans. The largest glacierized region and present-day contributor to sea level rise outside of the massive ice sheets is the Canadian Arctic. Recent work has shown that the glaciers of the southern Canadian Arctic (Baffin and Bylot Island) have experienced accelerated rates of ice loss in recent decades, but little is known regarding the spatial and temporal variations in rates of loss. For this study we examine in detail changes in the extent of the Penny Ice Cap (a proxy for ice loss) between 1969 and 2014 to better understand the climatic drivers of the recently observed accelerated rates of ice loss on Baffin Island. To do this, we reconstruct the extent of the ice cap for the year 1969 from historical maps and for the years 1985, 1995, 2010, and 2014 from Landsat 5 TM and Landsat 8 OLI imagery. We use 2009 SPOT HRS imagery and a novel extent comparison algorithm to assess the accuracy of glacier extents derived from Landsat imagery. Regional temperature and precipitation records were used to explain the spatial pattern of change. Due to large variation in elevations, hypsometry was also investigated as a contributor to differences in rates of change across the ice cap. Preliminary results show overall retreat throughout the ice cap but with regional differences in area and length change on either side of the Ice Cap divide.

Martian North Polar Water-Ice Clouds During the Viking Era

NASA Technical Reports Server (NTRS)

Tamppari, L. K.; Bass, D. S.

2000-01-01

The Viking Orbiters determined that the surface of Mars' northern residual cap consists of water ice. Observed atmospheric water vapor abundances in the equatorial regions have been related to seasonal exchange between reservoirs such as the polar caps, the regolith and between different phases in the atmosphere. Kahn modeled the physical characteristics of ice hazes seen in Viking Orbiter imaging limb data, hypothesizing that ice hazes provide a method for scavenging water vapor from the atmosphere and accumulating it into ice particles. Given that Jakosky found that these particles had sizes such that fallout times were of order one Martian sol, these water-ice hazes provided a method for returning more water to the regolith than that provided by adsorption alone. These hazes could also explain the rapid hemispheric decrease in atmospheric water in late northern summer as well as the increase during the following early spring. A similar comparison of water vapor abundance versus polar cap brightness has been done for the north polar region. They have shown that water vapor decreases steadily between L(sub s) = 100-150 deg while polar cap albedo increases during the same time frame. As a result, they suggested that late summer water-ice deposition onto the ice cap may be the cause of the cap brightening. This deposition could be due to adsorption directly onto the cap surface or to snowfall. Thus, an examination of north polar waterice clouds could lend insight into the fate of the water vapor during this time period. Additional information is contained in the original extended abstract.

A Chronology of Late-Glacial and Holocene Advances of Quelccaya Ice Cap, Peru, Based on 10Be and Radiocarbon Dating

NASA Astrophysics Data System (ADS)

Kelly, M. A.; Lowell, T. V.; Schaefer, J. M.

2007-12-01

The Quelccaya Ice Cap region in the southeastern Peruvian Andes (~13-14°S latitude) is a key location for the development of late-glacial and Holocene terrestrial paleoclimate records in the tropics. We present a chronology of past extents of Quelccaya Ice Cap based on ~thirty internally consistent 10Be dates of boulders on moraines and bedrock as well as twenty radiocarbon dates of organic material associated with moraines. Based on results from both dating methods, we suggest that significant advances of Quelccaya Ice Cap occurred during late-glacial time, at ~12,700-11,400 yr BP, and during Late Holocene time ~400-300 yr BP. Radiocarbon dating of organic material associated with moraines provides maximum and minimum ages for ice advances and recessions, respectively, thus providing an independent check on 10Be dates of boulders on moraines. The opportunity to use both 10Be and radiocarbon dating makes the Quelccaya Ice Cap region a potentially important low-latitude calibration site for production rates of cosmogenic nuclides. Our radiocarbon chronology provides a tighter constraint on maximum ages of late-glacial and Late Holocene ice advances. Upcoming field research will obtain organic material for radiocarbon dating to improve minimum age constrains for late-glacial and Late Holocene ice recessions.

Mars residual north polar cap - Earth-based spectroscopic confirmation of water ice as a major constituent and evidence for hydrated minerals

NASA Technical Reports Server (NTRS)

Clark, R. N.; Mccord, T. B.

1982-01-01

A description is presented of new earth-based reflectance spectra of the Martian north residual polar cap. The spectra indicate that the composition is at least mostly water ice plus another component with a 'gray' reflectance. The other minerals in the ice cap appear to be hydrated. The data were obtained with a cooled circular variable filter spectrometer on February 20, 1978, using the 2.2-m telescope on Mauna Kea, Hawaii. It is pointed out that the identification of water ice in the north polar cap alone does not indicate that water makes up all or even most of the bulk of the cap. Kieffer (1970) has shown that a small amount of water will mask the spectral features of CO2.

Proceedings of the Fourth International Conference on Mars Polar Science and Exploration

NASA Technical Reports Server (NTRS)

2006-01-01

Sessions in this conference include: Mars polar geology and glaciology; Mars and terrestrial radar investigations; Observations, nature, and evolution of the Martian seasonal polar caps; Mars' residual south polar cap; Climate change, ice core analysis, and the redistribution of volatiles on Mars; errestrial Mars analog environments; The Phoenix Scout mission and the nature of the near-polar environment; Moderated Discussion: Key Issues Regarding Phoenix Scout Mission and the nature of the near-polar environment; Panel Discussion: Key Issues in Mars Polar Science and Exploration; Mars Reconnaissance Orbiter investigations of the Martian polar regions and climate; Mars Polar Scout Mission concepts; and Panel Discussion: New perspectives on Mars polar science and exploration

Rapid onset of Little Ice Age summer cold in the northern North Atlantic derived from precisely dated ice cap records (Invited)

NASA Astrophysics Data System (ADS)

Miller, G. H.; Larsen, D.; Geirsdottir, A.; Refsnider, K. A.; Anderson, C.

2009-12-01

Precise radiocarbon dates on dead vegetation emerging beneath retreating non-erosive ice caps in NE Arctic Canada define the onset of ice cap growth, and provide a Holocene context for 20th Century warming. Although most plateau ice caps melted during the Medieval Warm Period, a few that are now disappearing remained intact since at least 350 AD. Little Ice Age ice cap inception occurred in two pulses, centered on 1250-1300 AD and around 1450 AD, with ice caps remaining in an expanded state until the warming of the past few decades. Ice cap inception occurred simultaneously (±10 years) over a 200 m elevational range, suggesting an abrupt onset of Little Ice Age cold, rather than a slow cooling over many decades. Similarly, a 3000 year annually resolved lacustrine record of glacier power and a complementary independent proxy for landscape instability in the highlands of central Iceland show an initial jump in both glacier power and landscape instability between 1250 and 1300 AD, with a second step-increase around 1450 AD, and dramatic increases in both proxies around 1800 AD, retracting in the 20th Century. A sub-decadal record of hillslope stability and within-lake primary productivity in sediments from a low-elevation lake in northern Iceland shows parallel changes at similar times. Sea ice proxies and historical records document the first appearance of sea ice around Iceland following Medieval time about 1250 AD. The similarity in the onset and intensification of Little Ice Age cold-weather proxies across a wide region of the northern North Atlantic suggests at least a regional driver of abrupt climate change. The time intervals for which these abrupt changes occur coincide with the three most intense episodes of multiple explosive volcanic eruptions that introduced large volumes of sulfate aerosols into the stratosphere during the past millennium. Although the direct impacts of volcanic aerosols have a duration of only a few years, the memory stored by the cooled ocean surface waters allows a cumulative effect to have a longer-term impact. To explain the apparent irreversible shift to colder summers following volcanic eruptions requires additional strong positive feedbacks, most likely a consequence of expanded sea ice cover.

Characterizing the Chemical and Physical Signature of the 2015-16 El Niño in the Quelccaya Ice Cap Snow and Ice to Calibrate Past ENSO Reconstructions.

NASA Astrophysics Data System (ADS)

Beaudon, E.; Barker, J. D.; Kenny, D. V.; Thompson, L. G.

2017-12-01

Pacific Sea Surface Temperature (SST) anomalies have reached +3°C in the Niño 3.4 region in November 2015 making this one of the strongest El Niños in 100 years. This warm phase of the El Niño - Southern Oscillation (ENSO) has pronounced differential impacts across the tropical Pacific as well as in South America. Peru statistically experienced flooding in the northern and central regions and drought conditions in the south on the Altiplano. However, the 2015-16 El Nino event led to drought throughout the Peruvian Andes. El Niño is a warm and dry episode, phase locked with the accumulation season on the Quelccaya Ice Cap (QIC) so that this strong event create conditions favorable for enhanced surface ablation and dry deposition of soluble and insoluble aerosols. Here we present new glaciochemical (major and organic ions, dust, black carbon, oxygen isotopes) results from two consecutive snow and ice sampling campaign on QIC framing the climax of the 2015/2016 El Niño episode in Peru. We allocate the ionic and black carbon sources and describe the biogenic and evaporitic contributions to Quelccaya snow chemistry under El Niño atmospheric conditions. Elution factors and ionic budgets are compared to those of the snow and ice samples collected prior to the El Niño initiation and thereby assess the magnitude of the impact of El Niño-induced post-depositional processes. Our results provide the database needed to verify that: 1) melt and percolation induced by El Niño is identifiable in the prior year's snow layer and thus might be calibrated to the El Niño's strength; and 2) the concentration and co-association of biogenic (e.g., NH4, black carbon) and evaporitic (salts) species is enhanced and detectable deeper in the ice and thereby might serve as a proxy for documenting past El Niño frequency. By capturing the chemical signature of a modern El Niño event occurring in a warming world, these results shed light on past ENSO variability preserved in ice core but also ensure better interpretation of other Andean ice cores records that could be hampered by melt.

High-amplitude, centennial-scale climate oscillations during the last glacial in the western Third Pole as recorded in the Guliya ice cap

NASA Astrophysics Data System (ADS)

Thompson, L. G.; Yao, T.; Mosley-Thompson, E.; Wu, G.; Davis, M. E.; Tian, L.; Lin, P. N.

2015-12-01

The Guliya ice cap, located in the Kunlun Mountains in the western Third Pole (TP) region near the northern limit of the southwest monsoon influence, may be the only non-polar ice field that provides detailed histories of climate and environment over the last glacial cycle. A continuous climate record from an ice core drilled in 1992 contains Eemian ice, and basal temperatures measured that year confirmed that the record was not being removed from the bottom. The δ18O record throughout Marine Isotope Stage 2 (MIS2) displays the occurrence of high-amplitude (~20‰) episodes of ~200-year periodicity, and the aerosol records suggest snow cover, regional vegetation and fire frequency that vary in synchrony. These oscillations might reflect the movement of the northernmost penetration of the monsoon precipitation through the Late Glacial Stage, which is restricted by the topographic barrier posed by the Kunlun range, and might also reflect solar-driven nonlinearities in the climate system such as sudden shifts in the jet stream. Recent model simulations suggest that glacial cooling over China was significantly amplified by stationary waves, and the Guliya MIS2 oscillations could reflect cyclical variability in these waves. These results are supported by clumped isotope thermometry of carbonates from the Chinese Loess Plateau, which indicate a 6 to 7oC decrease in Last Glacial Maximum summer temperatures. These studies will lead to a better understanding of the mechanisms driving such high-frequency, high-amplitude oscillations. A review of the 2015 Sino-American cooperative ice core drilling program on Guliya is presented. This program will serve as a flagship for the TP Environment Program, an international, multidisciplinary collaboration among professionals and students in 14 countries designed to investigate environmental changes across the TP. The rapidly warming TP contains ~46,000 glaciers that collectively hold one of Earth's largest stores of fresh water that feeds Asia's largest rivers and helps sustain 1.5 billion people. Information on the accelerating warming of these glaciers and the impact on future water resources in this important region is urgently needed to help guide mitigation and adaptation policies.

Landscape Evolution and the Reincarnation of the Residual CO2 Ice Cap of Mars

NASA Astrophysics Data System (ADS)

Byrne, S.; Zuber, M.

2006-12-01

Observations of the southern residual CO2 cap of Mars reveal a wide range of landforms including flat-floored quasi-circular pits with steep walls (dubbed Swiss-cheese features). Interannual comparisons show that these depressions are expanding laterally at rates of ~2m/yr to ~4m/yr, prompting suggestions of climate change. The residual CO2 ice cap is up to 10m thick and underlain by an involatile basement, it also contains layers roughly 2m thick representing different accumulation episodes in the recent past. Changes in the appearance of the residual ice between the Mariner 9 and Viking missions indicate that the top-most layer was deposited in that time-frame, soon after the global dust storm of 1971. The spatial density of the Swiss-cheese features, and the rate at which they expand, mean that it is unlikely that any part of the residual ice cap is older than a few centuries. Given this, we may ask: how can there be a residual cap present today for us to observe? To answer this and other questions we have developed a model to examine the evolution of a CO2 ice landscape. This model reproduces the morphologies and expansion rates seen in the actual residual CO2 ice cap. Our model results indicate that the fate of CO2 ice surfaces is controlled by their surface roughness. Surface roughness always increases with time, which results in an unstable situation. When the surface roughness exceeds a critical point small pits can begin to develop. The walls of these pits rapidly steepen and begin retreating which enlarges and deepens the pit. This situation always occurs even if the surface of the CO2 slab has a high enough albedo to have a net mass gain each year. Once these pits begin expanding they quickly erode the entire ice slab. When the underlying non-CO2 material is exposed, it will not frost over again if Mars were to repeat like clockwork every year. We conclude that interannual climatic variability is actually a requirement for the continued existence of a residual CO2 ice cap. We invoke unusual depositional episodes (which have a surface smoothing effect) after which the cap can begin accumulating mass and growing in thickness again. This continues until the surface roughness again exceeds a stable state and the process repeats itself. The thickness of the residual cap therefore oscillates on timescales of centuries. The total cap volume may also be affected by variations in residual cap extent. The cap is not 'stable' in the usual sense of the word, but instead is constantly being destroyed and recreated. Evidence suggests that these rejuvenating depositional events are linked to global dust storms. The 10m thick stratigraphic record thus provides a unique measure of interannual variability of the current climate, the expanding Swiss-cheese features do not indicate secular climate change, but instead are just part of the larger life-cycle of this ice deposit. We will report on this surface modeling which reproduces other morphologies within the residual cap and present a historical model based on combining our modeling with the feature sizes and ablation rates found within the present residual ice cap.

A GCM Recent History of Northern Martian Polar Layered Deposits: Contribution from Past Equatorial Ice Reservoirs

NASA Technical Reports Server (NTRS)

Levrard, B.; Laskar, J.; Montmessin, F.; Forget, F.

2005-01-01

Polar layered deposits are exposed in the walls of the troughs cutting the north polar cap of Mars. They consist of alternating ice and dust layers or layers of an ice-dust mixture with varying proportions and are found throughout the cap. Layers thickness ranges from meters to several tens of meters with an approximately 30 meter dominant wavelength. Although their formation processes is not known, they are presumed to reflect changes in ice and dust stability over orbital and axial variations. Intensive 3-D LMD GCM simulations of the martian water cycle have been thus performed to determine the annual rates of exchange of surface ice between the northern cap and tropical areas for a wide range of obliquity and orbital parameters values.These rates have been employed to reconstruct an history of the northern cap and test simple models of dust-ice layers formation over the last 10 Ma orbital variations. We use the 3-D water cycle model simulated by the 3-D LMD GCM with an intermediate grid resolution (7.5 longitude x 5.625 latitude) and 25 vertical levels. The dust opacity is constant and set to 0,15. No exchange of ice with regolith is allowed. The evolution of the northern cap over obliquity and orbital changes (eccentricity, Longitude of perihelion) has been recently described with this model. High summer insolation favors transfer of ice from the northern pole to the Tharsis and Olympus Montes, while at low obliquity, unstable equatorial ice is redeposited in high-latitude and polar areas of both hemisphere. The disappearance of the equatorial ice reservoir leads to a poleward recession of icy high latitude reservoirs, providing an additional source for the cap accumulation during each obliquity or orbital cycle. Furthering the efforts, a quantitative evolution of ice reservoirs is here investigated for various astronomical conditions.

Using Ice Predictions to Guide Submarines

DTIC Science & Technology

2016-01-01

the Arctic Cap Nowcast/ Forecast System (ACNFS) in September 2013. The ACNFS consists of a coupled ice -ocean model that assimilates available real...of the ice cover. The age of the sea ice serves as an indicator of its physical properties including surface roughness, melt pond coverage, and...the Arctic Cap Nowcast/Forecast System (ACNFS). Ice thickness is in meters for 11 September 2015. Thickness ranges from zero to five meters as shown

CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap

USGS Publications Warehouse

Kieffer, H.H.; Christensen, P.R.; Titus, T.N.

2006-01-01

The martian polar caps are among the most dynamic regions on Mars, growing substantially in winter as a significant fraction of the atmosphere freezes out in the form of CO2 ice. Unusual dark spots, fans and blotches form as the south-polar seasonal CO2 ice cap retreats during spring and summer. Small radial channel networks are often associated with the location of spots once the ice disappears. The spots have been proposed to be simply bare, defrosted ground; the formation of the channels has remained uncertain. Here we report infrared and visible observations that show that the spots and fans remain at CO2 ice temperatures well into summer, and must be granular materials that have been brought up to the surface of the ice, requiring a complex suite of processes to get them there. We propose that the seasonal ice cap forms an impermeable, translucent slab of CO2 ice that sublimates from the base, building up high-pressure gas beneath the slab. This gas levitates the ice, which eventually ruptures, producing high-velocity CO 2 vents that erupt sand-sized grains in jets to form the spots and erode the channels. These processes are unlike any observed on Earth. ?? 2006 Nature Publishing Group.

Earth tides, volcanos and climatic change

NASA Technical Reports Server (NTRS)

Roosen, R. G.; Harrington, R. S.; Giles, J.; Browning, I.

1976-01-01

The effect of variations in tidal stresses on the earth caused by the sun and moon on volcanic activity and climate is investigated. A statistically significant correlation is found between the derivatives of the envelopes of peak tidal stresses at high northern latitudes and the mean temperature of the Northern Hemisphere as reflected in oxygen isotope ratios in the Greenland ice cap. It is suggested that variations in tidal stresses cause changes in the amount of stratospheric dust produced by volcanic activity, which affects the thickness of the stratospheric dust veil and the atmospheric radiation balance. For a simple model, periodic variations in tidal stress account for 13% of the variance in the ice-core temperature record.

Exposure of Water Ice in the Northern Mid-lattitudes of Mars

NASA Technical Reports Server (NTRS)

Allen, Carlton C.; Kanner, Lisa C.

2007-01-01

Water ice is exposed in the martian north polar cap, and is occasionally exposed beyond the cap boundary. Orbital gamma ray spectrometry data strongly imply the presence of water ice within meters of the surface at latitudes north of approximately 60 deg. We have examined midlatitude areas of the northern plains displaying evidence of residual ice-rich layers, and report possible present-day exposures of ice. These exposures, if confirmed, could constrain the latitudinal and temporal stability of surface ice on Mars.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rose, Brian E. J.; Cronin, Timothy W.; Bitz, Cecilia M., E-mail: brose@albany.edu

Planetary obliquity determines the meridional distribution of the annual mean insolation. For obliquity exceeding 55°, the weakest insolation occurs at the equator. Stable partial snow and ice cover on such a planet would be in the form of a belt about the equator rather than polar caps. An analytical model of planetary climate is used to investigate the stability of ice caps and ice belts over the widest possible range of parameters. The model is a non-dimensional diffusive Energy Balance Model, representing insolation, heat transport, and ice−albedo feedback on a spherical planet. A complete analytical solution for any obliquity ismore » given and validated against numerical solutions of a seasonal model in the “deep-water” regime of weak seasonal ice line migration. Multiple equilibria and unstable transitions between climate states (ice-free, Snowball, or ice cap/belt) are found over wide swaths of parameter space, including a “Large Ice-Belt Instability” and “Small Ice-Belt Instability” at high obliquity. The Snowball catastrophe is avoided at weak radiative forcing in two different scenarios: weak albedo feedback and inefficient heat transport (favoring stable partial ice cover), or efficient transport at high obliquity (favoring ice-free conditions). From speculative assumptions about distributions of planetary parameters, three-fourths to four-fifths of all planets with stable partial ice cover should be in the form of Earth-like polar caps.« less

Evolving Technologies for In-Situ Studies of Mars Ice

NASA Technical Reports Server (NTRS)

Carsey, F. D.; Hecht, M. H.

2003-01-01

Icy sites on Mars continue to be of high scientific importance. These sites include the polar caps, the southern mid-latitude subsurface permafrost, and the seasonal frost. These sites have interest due to their roles in climate processes, past climates, surface and near-surface water, astrobiology, geomorphology, and other topics. As is the case for many planetary features, remote sensing, while of great value, cannot answer all questions; in-situ examination is essential, and the motivation for in-situ observations generally leads to the subsurface, which, fortunately, is accessible on Mars. It is clear in fact that a Mars polar cap subsurface mission is both scientifically compelling and practical. Recent data from orbiting platforms has provided a remarkable level of information about the Mars ice caps; we know, for example, the size, shape and annual cycle of the cap topography as well as we know that of Earth, and we have more information on stratification that we have of, for example, the ice of East Antarctica. To understand the roles that the Mars polar caps play, it is necessary to gather information on the ice cap surface, strata, composition and bed. In this talk the status of in-situ operations and observations will be summarized, and, since we have conveniently at hand another planet with polar caps, permafrost and ice, the role of testing and validation of experimental procedures on Earth will be addressed.

Polar Cap Formation on Ganymede

NASA Technical Reports Server (NTRS)

Pilcher, C. B.; Shaya, E. J.

1985-01-01

Since thermal migration is not an effective mechanism for water transport in the polar regions at the Galilean satellites, some other process must be responsible for the formation of Ganymede's polar caps. It is proposed that Ganymede's polar caps are the optical manifestation of a process that began with the distribution of an ice sheet over the surface of Ganymede. The combined processes of impact gardening and thermal migration led, in regions at latitudes less than 40 to 45 deg., to the burial of some fraction of this ice, the migration of some to the polar caps margins, and a depletion of free ice in the optical surface. At higher latitudes, no process was effective in removing ice from the optical surface, so the remanants of the sheet are visible today.

Recent Glaciers on Mars: Description and Solar System Perspective

NASA Astrophysics Data System (ADS)

Kargel, J. S.

2001-11-01

Active or recently active ice deposits occur on Mars at middle and high latitudes in fretted terrain, around massifs in highlands east of Hellas and in southern Argyre, on crater walls in the highlands, and in the south polar cap. Most mid-latitude icy flows are debris covered, apparently stagnant, and eroded by partial sublimation. Others are scarred by fresh crevasses and gullies, thus suggesting recent deformation and surface melting. Erosional features include a variety of small-scale relief elements due mainly to sublimation, but sublimation has not obliterated evidence of flow. Similar to terrestrial glaciers in many respects, there are also notable differences, especially in the nature of accumulation. Deformation of the south polar cap is indicated by folding, boudinage, strike-slip or normal faulting, forebulge tectonics near scarps, and thrust faulting. The north polar cap locally also exhibits flow indicators. The south cap's glacial features suggest interbedding of two or more types of ice of differing volatility and rheology, plus a locally deforming surficial dry-ice cap overlying the other materials. Major ice types may include two (or more) of the following, in order of highest to lowest mechanical strength: CO2 clathrate hydrate, water ice, water ice containing traces of liquid-soluble salts, water ice containing traces of solid-soluble acids, and CO2 ice; dust is another variable. Within our Solar System, the closest geomorphic analog to icy Martian flows are Earth's alpine glaciers, rock glaciers, and continental ice sheets, though key differences are apparent. If made dominantly of water ice, important and recent climatic shifts seem to be implicated. Ice-flow landforms also occur on some outer planet satellites; among them are Io, Europa, Enceladus, Ariel, and Triton. Volatile flows on these bodies may involve diverse materials, such as sulfur, water ice, hydrated salts, ammonia-water ices, and nitrogen ice. Most of these would not be suitable materials on Mars. This work was funded by grants from the NASA Mars Data Analysis Program.

Climate change: the evidence and our options.

PubMed

Thompson, Lonnie G

2010-01-01

Glaciers serve as early indicators of climate change. Over the last 35 years, our research team has recovered ice-core records of climatic and environmental variations from the polar regions and from low-latitude high-elevation ice fields from 16 countries. The ongoing widespread melting of high-elevation glaciers and ice caps, particularly in low to middle latitudes, provides some of the strongest evidence to date that a large-scale, pervasive, and, in some cases, rapid change in Earth's climate system is underway. This paper highlights observations of 20th and 21st century glacier shrinkage in the Andes, the Himalayas, and on Mount Kilimanjaro. Ice cores retrieved from shrinking glaciers around the world confirm their continuous existence for periods ranging from hundreds of years to multiple millennia, suggesting that climatological conditions that dominate those regions today are different from those under which these ice fields originally accumulated and have been sustained. The current warming is therefore unusual when viewed from the millennial perspective provided by multiple lines of proxy evidence and the 160-year record of direct temperature measurements. Despite all this evidence, plus the well-documented continual increase in atmospheric greenhouse gas concentrations, societies have taken little action to address this global-scale problem. Hence, the rate of global carbon dioxide emissions continues to accelerate. As a result of our inaction, we have three options: mitigation, adaptation, and suffering.

Climate Change: The Evidence and Our Options

PubMed Central

Thompson, Lonnie G

2010-01-01

Glaciers serve as early indicators of climate change. Over the last 35 years, our research team has recovered ice-core records of climatic and environmental variations from the polar regions and from low-latitude high-elevation ice fields from 16 countries. The ongoing widespread melting of high-elevation glaciers and ice caps, particularly in low to middle latitudes, provides some of the strongest evidence to date that a large-scale, pervasive, and, in some cases, rapid change in Earth's climate system is underway. This paper highlights observations of 20th and 21st century glacier shrinkage in the Andes, the Himalayas, and on Mount Kilimanjaro. Ice cores retrieved from shrinking glaciers around the world confirm their continuous existence for periods ranging from hundreds of years to multiple millennia, suggesting that climatological conditions that dominate those regions today are different from those under which these ice fields originally accumulated and have been sustained. The current warming is therefore unusual when viewed from the millennial perspective provided by multiple lines of proxy evidence and the 160-year record of direct temperature measurements. Despite all this evidence, plus the well-documented continual increase in atmospheric greenhouse gas concentrations, societies have taken little action to address this global-scale problem. Hence, the rate of global carbon dioxide emissions continues to accelerate. As a result of our inaction, we have three options: mitigation, adaptation, and suffering. PMID:22532707

The Contribution of Water Ice Clouds to the Water Cycle in the North Polar Region of Mars: Preliminary Analysis

NASA Technical Reports Server (NTRS)

Bass, D. S.; Tamppari, L. K.

2000-01-01

While it has long been known that Mars' north residual polar cap and the Martian regolith are significant sources of atmospheric water vapor, the amount of water vapor observed in the northern spring season by the Viking Mars Atmospheric Water Detector instrument (MAWD) cannot be attributed to cap and regolith sources alone. Kahn suggested that ice hazes may be the mechanism by which additional water is supplied to the Martian atmosphere. Additionally, a significant decrease in atmospheric water vapor was observed in the late northern summer that could not be correlated with the return of the cold seasonal C02 ice. While the detection of water ice clouds on Mars indicate that water exists in Mars' atmosphere in several different phases, the extent to which water ice clouds play a role in moving water through the Martian atmosphere remains uncertain. Work by Bass et. al. suggested that the time dependence of water ice cap seasonal variability and the increase in atmospheric water vapor depended on the polar cap center reaching 200K, the night time saturation temperature. Additionally, they demonstrated that a decrease in atmospheric water vapor may be attributed to deposition of water ice onto the surface of the polar cap; temperatures were still too warm at this time in the summer for the deposition of carbon dioxide. However, whether water ice clouds contribute significantly to this variability is unknown. Additional information is contained in original extended abstract.

CryoSat swath altimetry to measure ice cap and glacier surface elevation change

NASA Astrophysics Data System (ADS)

Tepes, P.; Gourmelen, N.; Escorihuela, M. J.; Wuite, J.; Nagler, T.; Foresta, L.; Brockley, D.; Baker, S.; Roca, M.; Shepherd, A.; Plummer, S.

2016-12-01

Satellite altimetry has been used extensively in the past few decades to observe changes affecting large and remote regions covered by land ice such as the Greenland and Antarctic ice sheets. Glaciers and ice caps have been studied less extensively due to limitation of altimetry over complex topography. However their role in current sea-level budgets is significant and is expected to continue over the next century and beyond (Gardner et al., 2011), particularly in the Arctic where mean annual surface temperatures have recently been increasing twice as fast as the global average (Screen and Simmonds, 2010). Radar altimetry is well suited to monitor elevation changes over land ice due to its all-weather year-round capability of observing ice surfaces. Since 2010, the Synthetic Interferometric Radar Altimeter (SIRAL) on board the European Space Agency (ESA) radar altimetry CryoSat (CS) mission has been collecting ice elevation measurements over glaciers and ice caps. Its Synthetic Aperture Radar Interferometric (SARIn) processing feature reduces the size of the footprint along-track and locates the across-track origin of a surface reflector in the presence of a slope. This offers new perspectives for the measurement of regions marked by complex topography. More recently, data from the CS-SARIn mode have been used to infer elevation beyond the point of closest approach (POCA) with a novel approach known as "swath processing" (Hawley et al., 2009; Gray et al., 2013; Christie et al., 2016; Smith et al., 2016). Together with a denser ground track interspacing of the CS mission, the swath processing technique provides unprecedented spatial coverage and resolution for space borne altimetry, enabling the study of key processes that underlie current changes of ice caps and glaciers. In this study, we use CS swath observations to generate maps of ice elevation change for selected ice caps and glaciers. We present a validation exercise and discuss the benefit of swath processing for assessing glaciers and ice caps changes and their contribution to changes in sea level.

South Polar Layers

NASA Image and Video Library

2016-08-25

Southern hemisphere spring has arrived at the south polar cap. The ice layers that make up the cap are easily seen in this image from NASA 2001 Mars Odyssey spacecraft. Southern hemisphere spring has arrived at the south polar cap. The ice layers that make up the cap are easily seen in this VIS image. Orbit Number: 64531 Latitude: -86.6334 Longitude: 97.7916 Instrument: VIS Captured: 2016-07-01 06:55 http://photojournal.jpl.nasa.gov/catalog/PIA20972

Present-day Exposures of Water Ice in the Northern Mid-latitudes of Mars

NASA Technical Reports Server (NTRS)

Allen, Carlton C.; Kanner, Lisa C.

2007-01-01

Water ice is exposed in the martian north polar cap, but is rarely exposed beyond the cap boundary. Orbital gamma ray spectrometry data strongly imply the presence of water ice within meters of the surface at latitudes north of approximately 60deg. We have examined mid-latitude areas of the northern plains displaying residual ice-rich layers, and report evidence of present-day surface exposures of water ice. These exposures, if confirmed, could con-strain the latitudinal and temporal stability of surface ice on Mars.

Modelled non-linear response to climate of Hardangerjøkulen ice cap, southern Norway, since the mid-Holocene

NASA Astrophysics Data System (ADS)

Åkesson, Henning; Nisancioglu, Kerim H.; Giesen, Rianne H.; Morlighem, Mathieu

2016-04-01

Glacier and ice cap volume changes currently amount to half of the total cryospheric contribution to sea-level rise and are projected to remain substantial throughout the 21st century. To simulate glacier behavior on centennial and longer time scales, models rely on simplified dynamics and tunable parameters for processes not well understood. Model calibration is often done using present-day observations, even though the relationship between parameters and parametrized processes may be altered for significantly different glacier states. In this study, we simulate the Hardangerjøkulen ice cap in southern Norway since the mid-Holocene, through the Little Ice Age (LIA) and into the future. We run an ensemble for both calibration and transient experiments, using a two-dimensional ice flow model with mesh refinement. For the Holocene, we apply a simple mass balance forcing based on climate reconstructions. For the LIA until 1962, we use geomorphological evidence and measured outlet glacier positions to find a mass balance history, while we use direct mass balance measurements from 1963 until today. Given a linear climate forcing, we show that Hardangerøkulen grew from ice-free conditions in the mid-Holocene, to its maximum LIA extent in a highly non-linear fashion. We relate this to local bed topography and demonstrate that volume and area of some but not all outlet glaciers, as well as the entire ice cap, become decoupled for several centuries during our simulation of the late Holocene, before co-varying approaching the LIA. Our model is able to simulate most recorded ice cap and outlet glacier changes from the LIA until today. We show that present-day Hardangerøkulen is highly sensitive to mass balance changes, and estimate that the ice cap will melt completely by the year 2100.

Martian Polar Caps: Folding, Faulting, Flowing Glaciers of Multiple Interbedded Ices

NASA Astrophysics Data System (ADS)

Kargel, J. S.

2001-12-01

The Martian south polar cap (permanent CO2 cap and polar layered deposits), exhibit abundant, varied, and widespread deformational phenomena. Folding and boudinage are very common. Strike-slip or normal faults are rarer. Common in the vicinity of major troughs and scarps are signs of convergent flow tectonics manifested as wrinkle-ridge-like surface folds, thrust faults, and viscous forebulges with thin-skinned extensional crevasses and wrinkle-ridge folds. Such flow convergence is predicted by theory. Boudinage and folding at the 300-m wavelength scale, indicating rheologically contrasting materials, is widely exposed at deep levels along erosional scarps. Independent morphologic evidence indicates south polar materials of contrasting volatility. Hence, the south polar cap appears to be a multiphase structure of interbedded ices. The north polar cap locally also exhibits flow indicators, though they are neither as common nor as varied as in the south. The large-scale quasi-spiral structure of the polar caps could be a manifestation of large-scale boudinage. According to this scenario, deep-level boudinage continuously originates under the glacial divide (the polar cap summit). Rod-like boudin structures are oriented transverse to flow and migrate outward with the large-scale flow field. Troughs develop over areas between major boudins. A dynamic competition, and possibly a rough balance, develops between the local flow field in the vicinity of a trough (which tends to close the trough by lateral closure and upwelling flow) and sublimation erosion (which tends to widen and deepen them). Over time, the troughs flow to the margins of the polar cap where they, along with other polar structures, are destroyed by sublimation. Major ice types contributing to rheological and volatility layering may include, in order of highest to lowest mechanical strength, CO2 clathrate hydrate, water ice containing inert/insoluble dust, pure water ice, water ice containing traces of liquid-soluble salts, water ice containing traces of solid-soluble acids, CO2 ice. This is also nearly the same sequence of highest to lowest melting/dissociation points, but it is different than the sequence of volatility. This geologic-structural interpretation and specific chemical models are amenable to testing by computational means and point the way toward future needed observations, including complete high-resolution imaging of the polar caps, measurement of flow fields (possibly by laser interferometry), mapping of subsurface structures (by radar and/or seismic methods), and determination of composition (by penetrators, drillers, or borers). New lab data are needed on the physical properties of candidate ices.

Destabilisation of an Arctic ice cap triggered by a hydro-thermodynamic feedback to summer-melt

NASA Astrophysics Data System (ADS)

Dunse, T.; Schellenberger, T.; Kääb, A.; Hagen, J. O.; Schuler, T. V.; Reijmer, C. H.

2014-05-01

Mass loss from glaciers and ice sheets currently accounts for two-thirds of the observed global sea-level rise and has accelerated since the 1990s, coincident with strong atmospheric warming in the Polar Regions. Here we present continuous GPS measurements and satellite synthetic aperture radar based velocity maps from the Austfonna ice cap, Svalbard, that demonstrate strong links between surface-melt and multiannual ice-flow acceleration. We identify a hydro-thermodynamic feedback that successively mobilizes stagnant ice regions, initially frozen to their bed, thereby facilitating fast basal motion over an expanding area. By autumn 2012, successive destabilization of the marine terminus escalated in a surge of the ice cap's largest drainage basin, Basin-3. The resulting iceberg discharge of 4.2 ± 1.6 Gt a-1 over the period April 2012 to May 2013 triples the calving loss from the entire ice cap. After accounting for the terminus advance, the related sea-level rise contribution of 7.2 ± 2.6 Gt a-1 matches the recent annual ice-mass loss from the entire Svalbard archipelago. Our study highlights the importance of dynamic glacier wastage and illuminates mechanisms that may trigger a sustained increase in dynamic glacier wastage or the disintegration of ice-sheets in response to climate warming, which is acknowledged but not quantified in global projections of sea-level rise.

Test results of Thermal Ice Cap prototype and final comments. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burley, W.

1982-01-01

The design and testing of an insulating cover, Ice Cap, for an ice rink are described. The radio-controlled reel system which houses, deploys, and harvests the 17,000 square feet of insulating material is essential to the success of the cover. Photographs showing the use of the system are included. (MHR)

77 FR 60651 - Airworthiness Directives; BAE Systems (Operations) Limited Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-04

... of the wing leading edge. This proposed AD would require a detailed inspection of the end caps on the... tube, and ice accretion on the wing leading edge or run-back ice, which could lead to a reduction in... leading edge anti- icing piccolo tube end caps on two aircraft. This was discovered during routine zonal...

78 FR 7259 - Airworthiness Directives; BAE SYSTEMS (OPERATIONS) LIMITED Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-02-01

... wing leading edge. This AD requires a detailed inspection of the end caps on the anti-icing piccolo... on the wing leading edge or run-back ice, which could lead to a reduction in the stall margin on... the loss of the wing leading edge anti- icing piccolo tube end caps on two aircraft. This was...

Early 21st-Century Mass loss of the North-Atlantic Glaciers and Ice Caps (Arne Richter Award for Outstanding Young Scientists Lecture)

NASA Astrophysics Data System (ADS)

Wouters, Bert; Ligtenberg, Stefan; Moholdt, Geir; Gardner, Alex S.; Noel, Brice; Kuipers Munneke, Peter; van den Broeke, Michiel; Bamber, Jonathan L.

2016-04-01

Historically, ice loss from mountain glaciers and ice caps has been one of the largest contributors to sea level rise over the last century. Of particular interest are the glaciers and ice caps in the North-Atlantic region of the Arctic. Despite the cold climate in this area, considerable melting and runoff occurs in summer. A small increase in temperature will have an immediate effect on these processes, so that a large change in the Arctic ice volume can be expected in response to the anticipated climate change in the coming century. Unfortunately, direct observations of glaciers are sparse and are biased toward glaciers systems in accessible, mostly maritime, climate conditions. Remote sensing is therefore essential to monitor the state of the the North-Atlantic glaciers and ice caps. In this presentation, we will discuss the progress that has been made in estimating the ice mass balance of these regions, with a particular focus on measurements made by ESA's Cryosat-2 radar altimeter mission (2010-present). Compared to earlier altimeter mission, Cryosat-2 provides unprecedented coverage of the cryosphere, with a resolution down to 1 km or better and sampling at monthly intervals. Combining the Cryosat-2 measurements with the laser altimetry data from ICESat (2003-2009) gives us a 12 yr time series of glacial mass loss in the North Atlantic. We find excellent agreement between the altimetry measurements and independent observations by the GRACE mission, which directly 'weighs' the ice caps, albeit at a much lower resolution. Mass loss in the region has increased from 120 Gigatonnes per year in 2003-2009 to roughly 140 Gt/yr in 2010-2014, with an important contribution from Greenland's peripheral glaciers and ice caps. Importantly, the mass loss is not stationary, but shows large regional interannual variability, with mass loss shifting between eastern and western regions from year to year. Comparison with regional climate models shows that these shifts can be explained by changes in surface mass balance processes, highlighting the sensitivity of the glaciers and ice caps to changes in the atmospheric circulation and underscoring the need for long-term observations of the region.

Rates of Deglaciation during the Last Glaciation and Holocene in the Cordillera Vilcanota-Quelccaya Ice Cap Region, Southeastern Perú

NASA Astrophysics Data System (ADS)

Mark, Bryan G.; Seltzer, Geoffrey O.; Rodbell, Donald T.; Goodman, Adam Y.

2002-05-01

Moraine chronology is combined with digital topography to model deglacial rates of paleoglacier volumes in both the Huancané Valley on the west side of the Quelccaya Ice Cap and the Upismayo Valley on the northwest side of the Cordillera Vilcanota. The fastest rates of deglaciation (39×10 -5 to 114×10 -5 km 3 yr -1 and 112×10 -5 to 247×10 -5 km 3 yr -1 for each valley, respectively) were calculated for the most recent paleoglaciers, corresponding to the last few centuries. These results are consistent with observations in the Venezuelan Andes showing high rates of deglaciation since the Little Ice Age. These rates also fall within the range of 20th century rates of deglaciation measured on the Quelccaya Ice Cap (29×10 -5 to 220×10 -5 km 3 yr -1, Brecher and Thompson, 1993; Thompson, 2000). These results imply that rates of deglaciation may fluctuate significantly over time and that high rates of deglaciation may not be exclusive to the late 20th century. Equilibrium line altitude (ELA) depressions for the ice volumes of the last glaciation modeled here were computed as 230 m for the Quelccaya Ice Cap and 170 m for the Cordillera Vilcanota. Maximum ELA depressions are lower than previously published: <500 m for the Cordillera Vilcanota and <400 m for the Quelccaya Ice Cap. These lower values could imply a topographic control over paleoglacier extent.

Microorganisms on comets, Europa, and the polar ice caps of Mars

NASA Astrophysics Data System (ADS)

Hoover, Richard B.; Pikuta, Elena V.

2004-02-01

Microbial extremophiles live on Earth wherever there is liquid water and a source of energy. Observations by ground-based observatories, space missions, and satellites have provided strong evidence that water ice exists today on comets, Europa, Callisto, and Ganymede and in the snow, permafrost, glaciers and polar ice caps of Mars. Studies of the cryoconite pools and ice bubble systems of Antarctica suggest that solar heating of dark rocks entrained in ice can cause localized melting of ice providing ideal conditions for the growth of microbial communities with the creation of micro-environments where trapped metabolic gasses produce entrained isolated atmospheres as in the Antarctic ice-bubble systems. It is suggested that these considerations indicate that several groups of microorganisms should be capable of episodic growth within liquid water envelopes surrounding dark rocks in cometary ices and the permafrost and polar caps of Mars. We discuss some of the types of microorganisms we have encountered within the permafrost and snow of Siberia, the cryoconite pools of Alaska, and frozen deep within the Antarctic ice sheet above Lake Vostok.

A Case for Microorganisms on Comets, Europa and the Polar Ice Caps of Mars

NASA Technical Reports Server (NTRS)

Hoover, Richard B.; Pikuta, Elena V.

2003-01-01

Microbial extremophiles live on Earth wherever there is liquid water and a source of energy. Observations by ground-based observatories, space missions, and satellites have provided strong evidence that water ice exists today on comets, Europa, Callisto, and Ganymede and in the snow, permafrost, glaciers and polar ice caps of Mars. Studies of the cryoconite pools and ice bubble systems of Antarctica suggest that solar heating of dark rocks entrained in ice can cause localized melting of ice providing ideal conditions for the growth of microbial communities with the creation of micro-environments where trapped metabolic gasses produce entrained isolated atmospheres as in the Antarctic ice-bubble systems. It is suggested that these considerations indicate that several groups of microorganisms should be capable of episodic growth within liquid water envelopes surrounding dark rocks in cometary ices and the permafrost and polar caps of Mars. We discuss some of the types of microorganisms we have encountered within the permafrost and snow of Siberia, the cryoconite pools of Alaska, and frozen deep within the Antarctic ice sheet above Lake Vostok.

Heavy metals in Antarctic ice from Law Dome: Initial results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hong, S.; Boutron, C.F.; Edwards, R.

1998-08-01

Pb, Cd, Cu, and Zn have been measured using ultraclean procedures in eight sections taken from two well-dated ice cores from Law Dome, an independent small size ice cap with high accumulation rate situated in the coastal area of East Antarctica. Seven sections were dated from the 1830s to 1940s and one was dated from three millennia ago. The data show that there are strong seasonal variations in the concentrations of Pb and Cd, with values {approximately} two- to four-fold higher in winter than in spring-summer. Evaluation of the contributions from the different sources suggests that contribution from sea saltmore » spray is relatively important, especially for Cd. Contribution from marine biogenic emissions could also be very significant. The importance of marine contributions is consistent with strong intrusions of marine air masses at this coastal site, especially during wintertime.« less

Textures in south polar ice cap #1

NASA Technical Reports Server (NTRS)

1998-01-01

Textures of the south polar permanent residual ice cap and polar layered terrains. This 30 x 29 km area image (frame 7709) is centered near 87 degrees south, 77 degrees west.

Figure caption from Science Magazine

Textures in south polar ice cap #2

NASA Technical Reports Server (NTRS)

1998-01-01

Textures of the south polar permanent residual ice cap and polar layered terrains. This 15 x 14 km area image (frame 7306) is centered near 87 degrees south, 341 degrees west.

Figure caption from Science Magazine

Holocene Activity of the Quelccaya Ice Cap: A Working Model

NASA Astrophysics Data System (ADS)

Lowell, T. V.; Smith, C. A.; Kelly, M. A.; Stroup, J. S.

2012-12-01

The patterns and magnitudes of past climate change in the topics are still under discussion. We contribute here by reporting on patterns of glacier length changes of the largest glacier in the tropics, Quelccaya Ice Cap (~13.9°S, 70.9°W, summit at 5645 m). This ice cap has several local domes that may have different patterns of length changes because of differing elevations of the domes (high to the north, lower to the south). Prior work (Mark et al. 2003, Abbott et al., 2004; Thompson et al., 2005; Buffen, et al., 2009), new radiocarbon ages, and stratigraphic and geomorphic relationships are used to determine the general pattern of length changes for the outlets from this ice cap. We exploit geomorphic relationships and present new radiocarbon ages on interpreted stratigraphic sections to determine the pattern of length changes for this ice cap. Ice retreated during late glacial times (Rodbell and Seltzer, 2000; Kelly et al., in press). By 11,400 yr BP it had reached a position ~1.2 km beyond its present (2000 AD) extent. While length during the early Holocene is problematic, present evidence permits, but does not prove, extents of 0.5 to 1.0 km down-valley from the present margin. Between 6400 and 4400 yr BP the ice cap was smaller than present, but it advanced multiple times during the late Holocene. Lengths of up to 1 km beyond present were achieved at 3400 yr BP and ~500 yr BP. Additionally, the ice advanced to 0.8 km beyond its present margin at 1600 yr BP. Because these glaciers were temperate, we take these lengths to represent primarily changes in temperature. This may suggest that lowering insolation values in the northern hemisphere during the Holocene provide a first order control on tropical temperatures. Alternatively, it may be that major reorganization of the topical circulation belts about 5000 yr BP yields two configurations of the QIC and hence Holocene temperatures - one at the present ice margin and and the second about 1 km beyond the present ice margin. In either case, the pulsating glacier lengths indicate a dynamic Holocene climate.

La calotta polare sud di Mars

NASA Astrophysics Data System (ADS)

di Giovanni, Giovanni

2006-06-01

The paper discusses the variations in the ice-retreat rate of the south polar cap of Mars in springtime during the 2003 and 2005 apparitions. For this we have measured the planetocentric cap amplitude on images of the Mars Sections of the Italian Union of Amateur Astronomers (UAI), the American Association of Lunar and Planetary Observers (ALPO) and ALPO Japan in the relevant Internet sites. A reasonable first approach to the problem was to perform a simple heat-balance model of Mars' ice cap including solar insolation, surface thermal emission, condensation and sublimation of carbon dioxide frost. The model doesn't include several important physical conditions, such as atmospherical absorption of radiation etc. and other components of ice (i.e. dust, H2O etc.). A suitable mathematical continue function θ(Ls) concerning the planetocentric amplitude of the cap as a function of the areocentric solar longitude on Mars (Ls) has been used to fit the experimental points in a classical diagram cap amplitude versus Ls. The correlation coefficient resulted 0.95. The second derivative of the function (d2θ/dLs2) suggests the existence of three important points during the spring recession: a) at Ls≍228° the highest sublimation rate is observe; b) at Ls≍245° (near perihelion) the highest retraction speed of the edge cap occurs, when the solar radiation flux over the south pole exceeds the flux over the equatorial zone; c) at Ls>285° the retraction speed of the cap's edge is constant. With the same function θ(Ls) we have worked out the ice thickness for every degrees in Ls, sublimation diurnal rate and total mass of seasonal cap. The ring of ice around to the pole, whose existence was suggested by Cross, was not revealed.

The role of water ice clouds in the Martian hydrologic cycle

NASA Technical Reports Server (NTRS)

James, Philip B.

1990-01-01

A one-dimensional model for the seasonal cycle of water on Mars has been used to investigate the direction of the net annual transport of water on the planet and to study the possible role of water ice clouds, which are included as an independent phase in addition to ground ice and water vapor, in the cycle. The calculated seasonal and spatial patterns of occurrence of water ice clouds are qualitatively similar to the observed polar hoods, suggesting that these polar clouds are, in fact, an important component of water cycle. A residual dry ice in the south acts as a cold trap which, in the absence of sources other than the caps, will ultimately attract the water ice from the north cap; however, in the presence of a source of water in northern midlatitudes during spring, it is possible that the observed distribution of vapor and ice can be in a steady state even if a residual CO2 cap is a permanent feature of the system.

High resolution and high precision on line isotopic analysis of Holocene and glacial ice performed in the field

NASA Astrophysics Data System (ADS)

Gkinis, V.; Popp, T. J.; Johnsen, S. J.; Blunier, T.; Bigler, M.; Stowasser, C.; Schüpbach, S.; Leuenberger, D.

2010-12-01

Ice core records as obtained from polar ice caps provide a wealth of paleoclimatic information. One of the main features of ice cores is their potential for high temporal resolution. The isotopic signature of the ice, expressed through the relative abundances of the two heavy isotopologues H218O and HD16O, is a widely used proxy for the reconstruction of past temperature and accumulation. One step further the combined information obtained from these two isotopologues, commonly referred to as the deuterium excess, can be utilized to infer additional information about the source of the precipitated moisture. Until very recently isotopic analysis of polar ice was performed with isotope Ratio Mass Spectrometry (IRMS) in a discrete fashion resulting in a high workload related to the preparation of samples. Most important though the available temporal resolution of the ice core was in many cases not fully exploited. In order to overcome these limitations we have developed a system that interfaces a commercially available IR laser cavity ring-down spectrometer tailored for water isotope analysis to a stream of liquid water as extracted from a continuously melted ice rod. The system offers the possibility for simultaneous δ18O and δD analysis with a sample requirement of approximately 0.1 ml/min. The system has been deployed in the field during the NEEM ice core drilling project on 2009 and 2010. In this study we present actual on line measurements of Holocene and glacial ice. We also discuss how parameters as the melt rate, acquisition rate and integration time affect the obtained precision and resolution and we describe data analysis techniques that can improve these last two parameters. By applying spectral methods we are able to quantify the smoothing effects imposed by diffusion of the sample in the sample transfer lines and the optical cavity of the instrument. We demonstrate that with an acquisition rate of 0.2 Hz we are able to obtain a precision of 0.5‰ and 0.15‰ for δD and δ18O respectively. This is comparable to the performance of traditional IRMS systems for δD but slightly less precise for δ18O. With this acquisition rate the system’s 3db bandwidth is 0.006 Hz. With a melt rate equal to 3 cm/min, the latter translates to signals with wavelengths of 8.3 cm. We will comment on the quality of the acquired ice core data and their potential use for dating, paleotemperature reconstruction, isotopic firn diffusion and deuterium excess studies.

Spring Slide

NASA Image and Video Library

2013-10-30

The North Polar region of Mars is capped with layers of water ice and dust, called the polar layered deposits. This permanent polar cap is covered in the winter with a layer of seasonal carbon dioxide ice as seen by NASA Mars Reconnaissance Orbiter.

Sea Ice Sensitivities in the 0.72 deg and 0.08 deg Arctic Cap Coupled HYCOM/CICE Models

DTIC Science & Technology

2014-09-30

1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Sea Ice Sensitivities in the 0.72°and 0.08° Arctic Cap...Arctic ice extent, which corresponds to the sea ice that remains during the summer minimum, has decreased over the years 1979–2007 by more than 10% per...Goosse et al. 2009) with the lowest observed sea ice extent in the satellite record (1979-present) occurring in September 2012 (Perovich et al. 2012

Life in ice: implications to astrobiology

NASA Astrophysics Data System (ADS)

Hoover, Richard B.; Pikuta, Elena V.

2009-08-01

During previous research expeditions to Siberia, Alaska and Antarctica, it was observed that glaciers and ice wedges contained bacterial cells that became motile as soon as the ice melted. This phenomenon of live bacteria in ice was first documented for microbes in ancient ice cores from Vostok, Antarctica. The first validly published species of Pleistocene bacteria alive on Earth today was Carnobacterium pleistocenium. This extremophile had remained for 32,000 years, encased in ice recently exposed in the Fox Tunnel of Alaska. These frozen bacteria began to swim as soon as the ice was thawed. Dark field microscopy studies revealed that large numbers of bacteria exhibited motility as soon as glacial ice was melted during our recent Expeditions to Alaska and Antarctica led to the conclusion that microbial life in ice was not a rare phenomenon. The ability of bacteria to remain alive while frozen in ice for long periods of time is of great significance to Astrobiology. In this paper, we describe the recent observations and advance the hypothesis that life in ice provides valuable clues to how we can more easily search for evidence of life on the Polar Caps of Mars, comets and other icy bodies of our Solar System. It is suggested that cryopanspermia may have played a far more important role in Origin of Life on Earth and the distribution of Life throughout the Cosmos and than previously thought possible.

Investigating Mars South Residual CO2 Cap with a Global Climate Model

NASA Technical Reports Server (NTRS)

Kahre, M. A.; Dequaire, J.; Hollingsworth, J. L.; Haberle, R. M.

2016-01-01

The CO2 cycle is one of the three controlling climate cycles on Mars. One aspect of the CO2 cycle that is not yet fully understood is the existence of a residual CO2 ice cap that is offset from the south pole. Previous investigations suggest that the atmosphere may control the placement of the south residual cap (e.g., Colaprete et al., 2005). These investigations show that topographically forced stationary eddies in the south during southern hemisphere winter produce colder atmospheric temperatures and increased CO2 snowfall over the hemisphere where the residual cap resides. Since precipitated CO2 ice produces higher surface albedos than directly deposited CO2 ice, it is plausible that CO2 snowfall resulting from the zonally asymmetric atmospheric circulation produces surface ice albedos high enough to maintain a residual cap only in one hemisphere. The goal of the current work is to further evaluate Colaprete et al.'s hypothesis by investigating model-predicted seasonally varying snowfall patterns in the southern polar region and the atmospheric circulation components that control them.

Mars Water Ice and Carbon Dioxide Seasonal Polar Caps: GCM Modeling and Comparison with Mars Express Omega Observations

NASA Technical Reports Server (NTRS)

Forget, F.; Levrard, B.; Montmessin, F.; Schmitt, B.; Doute, S.; Langevin, Y.; Bibring, J. P.

2005-01-01

To better understand the behavior of the Mars CO2 ice seasonal polar caps, and in particular interpret the the Mars Express Omega observations of the recession of the northern seasonal cap, we present some simulations of the Martian Climate/CO2 cycle/ water cycle as modeled by the Laboratoire de Meteorologie Dynamique (LMD) global climate model.

Towards Onboard Orbital Tracking of Seasonal Polar Volatiles on Mars

NASA Technical Reports Server (NTRS)

Wagstaff, Kiri L.; Castano, Rebecca; Chien, Steve; Ivanov, anton B.; Titus, Timothy N.

2005-01-01

Current conditions on Mars support both a residual polar cap, composed mainly of water ice, and a seasonal cap, composed of CO2, which appears and disappears each winter. Kieffer and Titus characterized the recession of the seasonal south polar cap using an arctangent curve fit based on data from the Thermal Emission Spectrometer on Mars Global Surveyor [1]. They also found significant interannual deviations, at the regional scale, in the recession rate [2]. Further observations will enable the refinement of our models of polar cap evolution in both hemispheres. We have developed the Bimodal Image Temperature (BIT) Histogram Analysis method for the automated detection and tracking of the seasonal polar ice caps on Mars. It is specifically tailored for possible use onboard a spacecraft. We have evaluated BIT on uncalibrated data collected by the Thermal Emission Imaging System (THEMIS) instrument [3] on the Mars Odyssey spacecraft. In this paper, we focus on the northern seasonal cap, but our approach is directly applicable to the future analysis of the southern seasonal ice cap as well.

Cold basal conditions during surges control flow of fringing Arctic ice caps in Greenland

NASA Astrophysics Data System (ADS)

Cook, Samuel; Christoffersen, Poul; Todd, Joe; Palmer, Steven

2017-04-01

Fringing ice caps separated from larger ice sheets are rarely studied, yet they are an important part of earth's cryosphere, which has become the largest source of global sea-level rise. Understanding marginal ice caps is crucial for being able to predict sea-level change as they are responsible for up to 20% of Greenland's mass loss for 2003-2008. Studies of fringing ice caps can furthermore provide useful insights into processes operating on glaciers that surge. Surging has been the focus of much recent glaciological work, especially with reference to thermal evolution of polythermal glaciers in High Mountain Asia and the High Arctic. This has shown that the classic divide between hydrologically-controlled surges ('hard-bed') in Alaska and thermally-regulated ('soft-bed') surges elsewhere is less stark than previously assumed. Studying marginal ice caps can therefore be valuable in several ways. The largest fringing ice cap in Greenland is Flade Isblink. Previous work has established that this ice cap is showing a range of dynamic behaviour, including subglacial lake drainage and varied patterns of mass-balance change. In particular, a substantial surge, assumed to be caused by a version of the thermally-regulated mechanism, occurred between 1996 and 2000, making the ice cap a useful case study for investigating this process. Here we investigate the surge on Flade Isblink using the open-source, Full-Stokes model Elmer/Ice to invert for basal conditions and englacial temperatures using the adjoint method. We specifically study steady-state conditions representative of the active surge phase in 2000, and the subsequent quiescent phase, using patterns of surface velocity observed in 2000, 2005, 2008 and 2015. Under constant geometry, temperature and geothermal heat, it is shown that surging increases basal freezing rates by over 60% across an area that is twice as large as the area over which the bed freezes in the quiescent phase. The process responsible for this is the conductive heat loss, which increases faster than frictional heat is produced. When the bed becomes weaker, basal conditions become colder despite faster basal sliding, resulting in steep basal ice temperature gradients, which transfer heat effectively from the bed into the ice. In contrast, we find the increase in frictional heat to be insufficient, because weaker basal conditions offset the effect of faster basal sliding. Hence, frictional heat cannot provide enough extra melting to maintain surge conditions. We hypothesise that this heat transfer mechanism terminates surges on Flade Isblink, irrespective of any thinning that would also occur. The latter is not included in our model, but is required in the classic soft-bed surge model. In the quiescent phase, lower temperature gradients reduce the conductive heat loss, while a stronger bed produces more frictional heat, favouring basal melting and a warm bed, which ultimately create the weak basal conditions that result in yet another surge, regardless of any change in ice thickness. Our results indicate that soft-bed surges may occur even if the surge-related change in glacier geometry is modest, making surging glaciers of this type similar to ice streams that stagnate and reactivate periodically.

The Mars water cycle at other epochs - Recent history of the polar caps and layered terrain

NASA Technical Reports Server (NTRS)

Jakosky, Bruce M.; Henderson, Bradley G.; Mellon, Michael T.

1993-01-01

A numerical model is presented of the integrated role of seasonal water cycle on the evolution of polar deposits on Mars over the last 10 million years. From the model, it is concluded that the only major difference between the polar caps which affects their long-term behavior is ultimately the difference in their elevations. Because of that difference, there is a preference for CO2 frost to stay longer on the northern polar cap. The average difference in sublimation at the caps results in a net south-to-north transport of water ice over long time scales. Superimposed on any long-term behavior is a transfer of water ice between the caps on the 10 exp 5 - 10 exp 6 yr time scales. The amount of water exchanged is small compared to the total ice content of the polar deposits.

The Mars water cycle at other epochs - Recent history of the polar caps and layered terrain

NASA Astrophysics Data System (ADS)

Jakosky, B. M.; Henderson, B. G.; Mellon, M. T.

1993-04-01

A numerical model is presented of the integrated role of seasonal water cycle on the evolution of polar deposits on Mars over the last 10 million years. From the model, it is concluded that the only major difference between the polar caps which affects their long-term behavior is ultimately the difference in their elevations. Because of that difference, there is a preference for CO2 frost to stay longer on the northern polar cap. The average difference in sublimation at the caps results in a net south-to-north transport of water ice over long time scales. Superimposed on any long-term behavior is a transfer of water ice between the caps on the 10 exp 5 - 10 exp 6 yr time scales. The amount of water exchanged is small compared to the total ice content of the polar deposits.

Crustal movements due to Iceland's shrinking ice caps mimic magma inflow signal at Katla volcano.

PubMed

Spaans, Karsten; Hreinsdóttir, Sigrún; Hooper, Andrew; Ófeigsson, Benedikt Gunnar

2015-05-20

Many volcanic systems around the world are located beneath, or in close proximity to, ice caps. Mass change of these ice caps causes surface movements, which are typically neglected when interpreting surface deformation measurements around these volcanoes. These movements can however be significant, and may closely resemble movements due to magma accumulation. Here we show such an example, from Katla volcano, Iceland. Horizontal movements observed by GPS on the flank of Katla have led to the inference of significant inflow of magma into a chamber beneath the caldera, starting in 2000, and continuing over several years. We use satellite radar interferometry and GPS data to show that between 2001 and 2010, the horizontal movements seen on the flank can be explained by the response to the long term shrinking of ice caps, and that erratic movements seen at stations within the caldera are also not likely to signify magma inflow. It is important that interpretations of geodetic measurements at volcanoes in glaciated areas consider the effect of ice mass change, and previous studies should be carefully reevaluated.

Ice-atmosphere interactions in the Canadian High Arctic: Implications for the thermo-mechanical evolution of terrestrial ice masses

NASA Astrophysics Data System (ADS)

Wohlleben, Trudy M. H.

Canadian High Arctic terrestrial ice masses and the polar atmosphere evolve codependently, and interactions between the two systems can lead to feedbacks, positive and negative. The two primary positive cryosphere-atmosphere feedbacks are: (1) The snow/ice-albedo feedback (where area changes in snow and/or ice cause changes in surface albedo and surface air temperatures, leading to further area changes in snow/ice); and (2) The elevation - mass balance feedback (where thickness changes in terrestrial ice masses cause changes to atmospheric circulation and precipitation patterns, leading to further ice thickness changes). In this thesis, numerical experiments are performed to: (1) quantify the magnitudes of the two feedbacks for chosen Canadian High Arctic terrestrial ice masses; and (2) to examine the direct and indirect consequences of surface air temperature changes upon englacial temperatures with implications for ice flow, mass flux divergence, and topographic evolution. Model results show that: (a) for John Evans Glacier, Ellesmere Island, the magnitude of the terrestrial snow/ice-albedo feedback can locally exceed that of sea ice on less than decadal timescales, with implications for glacier response times to climate perturbations; (b) although historical air temperature changes might be the direct cause of measured englacial temperature anomalies in various glacier and ice cap accumulation zones, they can also be the indirect cause of their enhanced diffusive loss; (c) while the direct result of past air temperature changes has been to cool the interior of John Evans Glacier, and its bed, the indirect result has been to create and maintain warm (pressure melting point) basal temperatures in the ablation zone; and (d) for Devon Ice Cap, observed mass gains in the northwest sector of the ice cap would be smaller without orographic precipitation and the mass balance---elevation feedback, supporting the hypothesis that this feedback is playing a role in the evolution of the ice cap.

Numerical modeling of Drangajökull Ice Cap, NW Iceland

NASA Astrophysics Data System (ADS)

Anderson, Leif S.; Jarosch, Alexander H.; Flowers, Gwenn E.; Aðalgeirsdóttir, Guðfinna; Magnússon, Eyjólfur; Pálsson, Finnur; Muñoz-Cobo Belart, Joaquín; Þorsteinsson, Þorsteinn; Jóhannesson, Tómas; Sigurðsson, Oddur; Harning, David; Miller, Gifford H.; Geirsdóttir, Áslaug

2016-04-01

Over the past century the Arctic has warmed twice as fast as the global average. This discrepancy is likely due to feedbacks inherent to the Arctic climate system. These Arctic climate feedbacks are currently poorly quantified, but are essential to future climate predictions based on global circulation modeling. Constraining the magnitude and timing of past Arctic climate changes allows us to test climate feedback parameterizations at different times with different boundary conditions. Because Holocene Arctic summer temperature changes have been largest in the North Atlantic (Kaufman et al., 2004) we focus on constraining the paleoclimate of Iceland. Glaciers are highly sensitive to changes in temperature and precipitation amount. This sensitivity allows for the estimation of paleoclimate using glacier models, modern glacier mass balance data, and past glacier extents. We apply our model to the Drangajökull ice cap (~150 sq. km) in NW Iceland. Our numerical model is resolved in two-dimensions, conserves mass, and applies the shallow-ice-approximation. The bed DEM used in the model runs was constructed from radio echo data surveyed in spring 2014. We constrain the modern surface mass balance of Drangajökull using: 1) ablation and accumulation stakes; 2) ice surface digital elevation models (DEMs) from satellite, airborne LiDAR, and aerial photographs; and 3) full-stokes model-derived vertical ice velocities. The modeled vertical ice velocities and ice surface DEMs are combined to estimate past surface mass balance. We constrain Holocene glacier geometries using moraines and trimlines (e.g., Brynjolfsson, etal, 2014), proglacial-lake cores, and radiocarbon-dated dead vegetation emerging from under the modern glacier. We present a sensitivity analysis of the model to changes in parameters and show the effect of step changes of temperature and precipitation on glacier extent. Our results are placed in context with local lacustrine and marine climate proxies as well as with glacier extent and volume changes across the North Atlantic.

Glacial-marine sediments record ice-shelf retreat during the late Holocene in Beascochea Bay on the western margin of the Antarctic Peninsula

NASA Astrophysics Data System (ADS)

Hardin, L. A.; Wellner, J. S.

2010-12-01

Beascochea Bay has an overall rapid rate of sedimentation due to retreating fast-flowing ice, and thus contains high-resolution records of Antarctica’s glacial and climate history. Beascochea Bay is a 16 km long by 8 km wide bay located on the western margin of the Antarctica Peninsula, centered between Anvers Island and Renaud Island, but open to the Bellingshausen Sea. Currently, three tidewater glaciers draining the Bruce Plateau of Graham Land enter into the fjords of Beascochea Bay, releasing terrigenous sediments which have left a record of the fluctuations of the Antarctic Peninsula Ice Cap since the grounded ice decoupled from the seafloor after the last glacial maximum. These three glaciers have played a significant role in providing sediment to the main basin, allowing a detailed sediment facies analysis to be conducted from eight sediment cores which were collected during the austral summer of 2007. Pebbly silty clay sediment cores, along with 3.5 kHz seismic data and multibeam swath bathymetry data, are integrated to reconstruct a glacial retreat timeline for the middle to late Holocene, which can be compared to the recent retreat rates over the last century. Paleoenvironment of deposition is determined by mapping lateral facies changes from the side fjords (proximal) to the outer basin (distal), as each region records the transition from glacial-marine sediments to open-marine sediments. As the ice retreated from the outer basin to the inner basin, and most recently leaving the side fjords, each facies deposited can be age-constrained by radiocarbon, 210Pb, and 137Cs dating methods. A distinct 137Cs signal is readily seen in two kasten cores from a side fjord and the inner basin of Beascochea Bay. This dating method revealed an average sedimentation rate of 2.7 mm per year for approximately the last century, which is comparable to 210Pb rates obtained in other studies. Lithology variations in each sediment core record indications of ice-shelf influence in Beascochea Bay throughout the Holocene deglaciation. The distinctively laminated sub-ice shelf facies can be clearly seen in the x-rays of these cores, and can be easily distinguished from the poorly sorted glacial-marine facies and the greenish finer-grained facies deposited in open-marine conditions. A 14 m long sediment core taken from the outer basin of Beascochea Bay recovered the greatest length of sediment and dates back to the middle Holocene. X-rays of this core show a possible mid-Holocene retreat of the ice shelf followed by intermittent advance and retreat that precedes the most recent retreat. The inner basin of Beascochea Bay has been without an ice shelf for the last 200 years, based on the sedimentation rates of the last century projected downcore.

Detailed history of atmospheric trace elements from the Quelccaya ice core (Southern Peru) during the last 1200 years

NASA Astrophysics Data System (ADS)

Uglietti, C.; Gabrielli, P.; Thompson, L. G.

2013-12-01

The recent increase in trace element concentrations, for example Cr, Cu, Zn, Ag, Pb, Bi, and U, in polar snow and ice has provided compelling evidence of a hemispheric change in atmospheric composition since the nineteenth century. This change has been concomitant with the expansion of the Industrial Revolution and points towards an anthropogenic source of trace elements in the atmosphere. There are very few low latitude trace element ice core records and these are believed to be sensitive to perturbations of regional significance. To date, these records have not been used to document a preindustrial anthropogenic impact on atmospheric composition at low latitudes. Ice cores retrieved from the tropical Andes are particularly interesting because they have the potential to reveal detailed information about the evolution and environmental consequences of mineral exploitation related to the Pre Inca Civilizations, the Inca Empire (1438-1533 AD) and the subsequent Spanish invasion and dominance (1532-1833 AD). The chemical record preserved in the ice of the Quelccaya ice cap (southern Peruvian Andes) offers the exceptional opportunity to geochemically constrain the composition of the tropical atmosphere at high resolution over the last ~1200 years. Quantification of twenty trace elements (Ag, Al, As, Bi, Cd, Co, Cr, Cu, Fe, Mn, Mo, Pb, Rb, Sb, Sn, Ti, Tl, U, V, and Zn) was performed by ICP-SFMS over 105 m of the Quelccaya North Dome core (5600 m asl, 128.57 m) by analyzing 2450 samples. This provides the first atmospheric trace element record in South America spanning continuously and at high resolution for the time period between 1990 and 790 AD. Ag, As, Bi, Cd, Cr, Co, Cu, Mn, Mo, Sb, Sn, Pb and Zn show increases in concentration and crustal enrichment factor starting at different times between 1450 and 1550 AD, in concomitance with the expansions of the Inca Empire and, subsequently, the Spanish Empire well before the inception of the Industrial Revolution. This indicates that there have been additional anthropogenic sources that have impacted the South American atmosphere during the past ~550 years. Furthermore, As, Bi and Pb record shows, the two most significant increases have occurred in the 20th century, one beginning in ~1905 AD and peaking in the 1920s and the second beginning in ~1955 AD and peaking in the 1970s. Comparison with other trace element records from Greenland and Antarctica reveals concomitant peaks of different amplitude in Pb concentration and crustal enrichment factor, possibly pointing to an unexpected larger than regional scale significance for the Quelccaya ice core record during the last century. In conclusion, the Quelccaya ice core indicates that societal and industrial development influenced the atmospheric composition in South America, from different large scale sources, during the last ~550 years. This is the first time that a low latitude ice core record has been used to reconstruct pre-industrial anthropogenic forcing on the atmosphere.

Life in Ice: Implications to Astrobiology

NASA Technical Reports Server (NTRS)

Hoover, Richard B.

2009-01-01

During the 2008 Tawani International Expedition Schirmacher Oasis/Lake Untersee Antarctica Expedition, living and instantly motile bacteria were found in freshly thawed meltwater from ice of the Schirmacher Oasis Lakes, the Anuchin Glacier ice and samples of the that perennial ice sheet above Lake Untersee. This phenomenon of living bacteria encased in ice had previously been observed in the 32,000 year old ice of the Fox Tunnel. The bacteria found in this ice included the strain FTR1T which was isolated and published as valid new species (Carnobacterium pleistocenium) the first validly published living Pleistocene organism still alive today. Living bacteria were also extracted from ancient ice cores from Vostok, Antarctica. The discovery that many strains of bacteria are able to survive and remain alive while frozen in ice sheets for long periods of time may have direct relevance to Astrobiology. The abundance of viable bacteria in the ice sheets of Antarctica suggests that the presence of live bacteria in ice is common, rather than an isolated phenomenon. This paper will discuss the results of recent studies at NSSTC of bacteria cryopreserved in ice. This paper advances the hypothesis that cryopreserved cells, and perhaps even viable bacterial cells, may exist today--frozen in the water-ice of lunar craters, the Polar Caps or craters of Mars; or in the permafrost of Mars; ice and rocks of comets or water bearing asteroids; or in the frozen crusts of the icy moons of Jupiter and Saturn. The existence of bacterial life in ice suggests that it may not be necessary to drill through a thick ice crust to reach liquid water seas deep beneath the icy crusts of Europa, Ganymede and Enceladus. The presence of viable bacteria in the ice of the Earth s Polar Caps suggests that the possibility that cryo-panspermia (i.e., the trans-planetary transfer of microbial life by impact ejection/spallation of bacteria-rich polar ice masses) deserves serious consideration and study as a possible natural phenomenon of the solar system that may have played a profoundly important role in the Origin of Life on Earth and the Distribution of Life in the Cosmos. The paper concludes with a consideration of the protective properties of ice by absorption of UV-B, UV-C, h-rays, gamma-rays and the high energy proton environment of the Jupiter Radiation Belt. A proposed instrument that may provide additional data on the potential survivability of microbial extremophiles encased in ice and subjected to the simulated space environment will be briefly described.

Observations of the north polar water ice annulus on Mars using THEMIS and TES

USGS Publications Warehouse

Wagstaff, K.L.; Titus, T.N.; Ivanov, A.B.; Castano, R.; Bandfield, J.L.

2008-01-01

The Martian seasonal CO2 ice caps advance and retreat each year. In the spring, as the CO2 cap gradually retreats, it leaves behind an extensive defrosting zone from the solid CO2 cap to the location where all CO2 frost has sublimated. We have been studying this phenomenon in the north polar region using data from the THermal EMission Imaging System (THEMIS), a visible and infra-red (IR) camera on the Mars Odyssey spacecraft, and the Thermal Emission Spectrometer (TES) on Mars Global Surveyor. Recently, we discovered that some THEMIS images of the CO2 defrosting zone contain evidence for a distinct defrosting phenomenon: some areas just south of the CO2 cap edge are too bright in visible wavelengths to be defrosted terrain, but too warm in the IR to be CO2 ice. We hypothesize that we are seeing evidence for a seasonal annulus of water ice (frost) that recedes with the seasonal CO2 cap, as predicted by previous workers. In this paper, we describe our observations with THEMIS and compare them to simultaneous observations by TES and OMEGA. All three instruments find that this phenomenon is distinct from the CO2 cap and most likely composed of water ice. We also find strong evidence that the annulus widens as it recedes. Finally, we show that this annulus can be detected in the raw THEMIS data as it is collected, enabling future long-term onboard monitoring. ?? 2007.

Glaciological reconstruction of Holocene ice margins in northwestern Greenland

NASA Astrophysics Data System (ADS)

Birkel, S. D.; Osterberg, E. C.; Kelly, M. A.; Axford, Y.

2014-12-01

The past few decades of climate warming have brought overall margin retreat to the Greenland Ice Sheet. In order to place recent and projected changes in context, we are undertaking a collaborative field-modeling study that aims to reconstruct the Holocene history of ice-margin fluctuation near Thule (~76.5°N, 68.7°W), and also along the North Ice Cap (NIC) in the Nunatarssuaq region (~76.7°N, 67.4°W). Fieldwork reported by Kelly et al. (2013) reveals that ice in the study areas was less extensive than at present ca. 4700 (GIS) and ca. 880 (NIC) cal. years BP, presumably in response to a warmer climate. We are now exploring Holocene ice-climate coupling using the University of Maine Ice Sheet Model (UMISM). Our approach is to first test what imposed climate anomalies can afford steady state ice margins in accord with field data. A second test encompasses transient simulation of the Holocene, with climate boundary conditions supplied by existing paleo runs of the Community Climate System Model version 4 (CCSM4), and a climate forcing signal derived from Greenland ice cores. In both cases, the full ice sheet is simulated at 10 km resolution with nested domains at 0.5 km for the study areas. UMISM experiments are underway, and results will be reported at the meeting.

What Lies Below a Martian Ice Cap

NASA Technical Reports Server (NTRS)

2008-01-01

[figure removed for brevity, see original site] Click on image for larger annotated version

This image (top) taken by the Shallow Radar instrument on NASA's Mars Reconnaissance Orbiter reveals the layers of ice, sand and dust that make up the north polar ice cap on Mars. It is the most detailed look to date at the insides of this ice cap. The colored map below the radar picture shows the topography of the corresponding Martian terrain (red and white represent higher ground, and green and yellow lower).

The radar image reveals four never-before-seen thick layers of ice and dust separated by layers of nearly pure ice. According to scientists, these thick ice-free layers represent approximately one-million-year-long cycles of climate change on Mars caused by variations in the planet's tilted axis and its eccentric orbit around the sun. Adding up the entire stack of ice gives an estimated age for the north polar ice cap of about 4 million years a finding that agrees with previous theoretical estimates. The ice cap is about 2 kilometers (1.2 miles) thick.

The radar picture also shows that the boundary between the ice layers and the surface of Mars underneath is relatively flat (bottom white line on the right). This implies that the surface of Mars is not sagging, or bending, under the weight of the ice cap and this, in turn, suggests that the planet's lithosphere, a combination of the crust and the strong parts of the upper mantle, is thicker than previously thought.

A thicker lithosphere on Mars means that temperatures increase more gradually with depth toward the interior. Temperatures warm enough for water to be liquid are therefore deeper than previously thought. Likewise, if liquid water does exist in aquifers below the surface of Mars, and if there are any organisms living in that water, they would have to be located deeper in the planet.

The topography data are from Mars Orbiter Laser Altimeter, which was flown on NASA's Mars Global Surveyor mission.

NPLD stands for the north polar layered deposits.

BU stands for basal unit, an ice-sand deposit that lies beneath parts of the north polar layered deposits.

The Shallow Radar instrument was provided by the Italian Space Agency. Its operations are led by the University of Rome and its data are analyzed by a joint U.S.-Italian science team. JPL, a division of the California Institute of Technology, Pasadena, manages the Mars Reconnaissance Orbiter for the NASA Science Mission Directorate, Washington.

Glaciers of Greenland

USGS Publications Warehouse

Williams, Richard S.; Ferrigno, Jane G.

1995-01-01

Landsat imagery, combined with aerial photography, sketch maps, and diagrams, is used as the basis for a description of the geography, climatology, and glaciology, including mass balance, variation, and hazards, of the Greenland ice sheet and local ice caps and glaciers. The Greenland ice sheet, with an estimated area of 1,736,095+/-100 km2 and volume of 2,600,000 km3, is the second largest glacier on the planet and the largest relict of the Ice Age in the Northern Hemisphere. Greenland also has 48,599+/-100 km2 of local ice caps and other types of glaciers in coastal areas and islands beyond the margin of the ice sheet.

Effects of deliquescent salts in soils of polar Mars on the flow of the Northern Ice Cap

NASA Astrophysics Data System (ADS)

Fisher, D. A.; Hecht, M. H.; Kounaves, S.; Catling, D.

2008-12-01

The discovery of substantial amounts of magnesium and perchlorate by Phoenix' "Wet Chemistry Lab" (WCL) in the soil of Polar Mars suggests that magnesium perchlorate could be the dominant salt in the polar region's soils. This prospect opens some unexpected doors for moving liquid water around at temperatures as low as -68C. In its fully hydrated form ,this salt water mixture has a high density (~ 1700 kgm /cubic meter) (Besley and Bottomley,1969) and a freezing point of -68C (Pestova et al., 2005).This perchlorate is very deliquescent and gives off heat as it melts ice. About 1.8 gram of ice can be 'melted' by 1 gm of pure magnesium perchlorate . If the reported 1 percent perchlorate is typical of polar soils and if 5 percent of the Northern Permanent Ice Cap is soil then the perchorate , makes up about 0.0005 the of the ice cap. Given the average thickness of the ice cap is about 2000 meters,this suggests there enough perchorate in the ice cap to generate about 2m of salty water at the bed. Because of its density the perclorate salty water would pool over impervious layers and make the bed into a perchorate sludge that could be mobilized and deformed by the overburden of ice. The deformation of mobile beds is a well known phenomenon on some terrestrial glaciers presently and was thought to have played a major role during the Wisconsinan ice age (Fisher et al., 1985) . The perchorate sludge would be deformed and moved outwards possibly resulting its re-introduction to the polar environment. Having a deliquescent salt sludge at the bed whose melting point is -68C would mean that the ice cap could slide on its deformable bed while the ice itself was still very cold and stiff . This possibility has been modeled with a 2D time varying model . Adding the deformable bed material allows ice cap motion even at ice temperatures cold enough to generate and preserve the scarp/trough features. When the perchlorate formation mechanisms and rates are known the ultimate importance of it in the water cycle of Mars will be clearer. The ice cap has long been thought of as a possible re-charge area for the deep water return flow (Clifford , 1987) . If perchlorate is formed sufficiently quickly, this view would be strengthened in spite of the low temperatures. Clifford S.M. 1987. Polar basal melting. JGR. Vol. 92, No. B9, pp 9135-9152. Besley L. M. and G.A. Bottomley. 1969. The water vapour equilibria over magnesium perchlorate hydrates. Journal of Chemical Thermodynamics. 1, pp13-19. Fisher, D.A., Reeh, N., and Langley, K. 1985. Objective reconstructions of the late Wisconsinan Laurentide Ice Sheet and the significance of deformable beds. Géographie physique et Quaternaire, v. 39, no. 3, p. 229-238. Pestova O. N.,Myund L.A.,Khripun M.K. and A.V. Prigaro. 2005. Polythermal study of systems M(ClO4)2-H2O (M2+=Mg2+, Ca2+, Sr2+, Ba2+). Russian Journal of Applied Chemistry , Vol.78.No.3,pp409-413. class="ab'>

Erosion patterns produced by the paleo Haizishan ice cap, SE Tibetan Plateau

NASA Astrophysics Data System (ADS)

Fu, P.; Stroeven, A. P.; Harbor, J.; Hättestrand, C.; Heyman, J.; Caffee, M. W.

2017-12-01

Erosion is a primary driver of landscape evolution, topographic relief production, geochemical cycles, and climate change. Combining in situ 10Be and 26Al exposure age dating, geomorphological mapping, and field investigations, we examine glacial erosion patterns of the almost 4,000 km2 paleo Haizishan ice cap on the southeastern Tibetan Plateau. Our results show that ice caps on the low relief Haizishan Plateau produced a zonal pattern of landscape modification. In locations where apparent exposure ages on bedrock are consistent with the last deglaciation, complete resetting of the cosmogenic exposure age clock indicates glacial erosion of at least a few meters. However, older apparent exposure ages on bedrock in areas known to have been covered by the paleo ice cap during the Last Glacial Maximum indicate inheritance and thus limited glacial erosion. Inferred surface exposure ages from cosmogenic depth profiles through two saprolites vary from resetting and thus saprolite profile truncation to nuclide inheritance indicating limited erosion. Finally, significant nuclide inheritance in river sand samples from basins on the scoured plateau surface also indicate limited glacial erosion during the last glaciation. Hence, for the first time, our study shows clear evidence of preservation under non-erosive ice on the Tibetan Plateau. As patterns of glacial erosion intensity are largely driven by the basal thermal regime, our results confirm earlier inferences from geomorphology for a concentric basal thermal pattern for the paleo Haizishan ice cap during the LGM.

Field-calibrated model of melt, refreezing, and runoff for polar ice caps: Application to Devon Ice Cap

NASA Astrophysics Data System (ADS)

Morris, Richard M.; Mair, Douglas W. F.; Nienow, Peter W.; Bell, Christina; Burgess, David O.; Wright, Andrew P.

2014-09-01

Understanding the controls on the amount of surface meltwater that refreezes, rather than becoming runoff, over polar ice masses is necessary for modeling their surface mass balance and ultimately for predicting their future contributions to global sea level change. We present a modified version of a physically based model that includes an energy balance routine and explicit calculation of near-surface meltwater refreezing capacity, to simulate the evolution of near-surface density and temperature profiles across Devon Ice Cap in Arctic Canada. Uniquely, our model is initiated and calibrated using high spatial resolution measurements of snow and firn densities across almost the entire elevation range of the ice cap for the summer of 2004 and subsequently validated with the same type of measurements obtained during the very different meteorological conditions of summer 2006. The model captures the spatial variability across the transect in bulk snowpack properties although it slightly underestimates the flow of meltwater into the firn of previous years. The percentage of meltwater that becomes runoff is similar in both years; however, the spatial pattern of this melt-runoff relationship is different in the 2 years. The model is found to be insensitive to variation in the depth of impermeable layers within the firn but is very sensitive to variation in air temperature, since the refreezing capacity of firn decreases with increasing temperature. We highlight that the sensitivity of the ice cap's surface mass balance to air temperature is itself dependent on air temperature.

Glacial isostatic uplift of the European Alps

PubMed Central

Mey, Jürgen; Scherler, Dirk; Wickert, Andrew D.; Egholm, David L.; Tesauro, Magdala; Schildgen, Taylor F.; Strecker, Manfred R.

2016-01-01

Following the last glacial maximum (LGM), the demise of continental ice sheets induced crustal rebound in tectonically stable regions of North America and Scandinavia that is still ongoing. Unlike the ice sheets, the Alpine ice cap developed in an orogen where the measured uplift is potentially attributed to tectonic shortening, lithospheric delamination and unloading due to deglaciation and erosion. Here we show that ∼90% of the geodetically measured rock uplift in the Alps can be explained by the Earth’s viscoelastic response to LGM deglaciation. We modelled rock uplift by reconstructing the Alpine ice cap, while accounting for postglacial erosion, sediment deposition and spatial variations in lithospheric rigidity. Clusters of excessive uplift in the Rhône Valley and in the Eastern Alps delineate regions potentially affected by mantle processes, crustal heterogeneity and active tectonics. Our study shows that even small LGM ice caps can dominate present-day rock uplift in tectonically active regions. PMID:27830704

Glacial isostatic uplift of the European Alps.

PubMed

Mey, Jürgen; Scherler, Dirk; Wickert, Andrew D; Egholm, David L; Tesauro, Magdala; Schildgen, Taylor F; Strecker, Manfred R

2016-11-10

Following the last glacial maximum (LGM), the demise of continental ice sheets induced crustal rebound in tectonically stable regions of North America and Scandinavia that is still ongoing. Unlike the ice sheets, the Alpine ice cap developed in an orogen where the measured uplift is potentially attributed to tectonic shortening, lithospheric delamination and unloading due to deglaciation and erosion. Here we show that ∼90% of the geodetically measured rock uplift in the Alps can be explained by the Earth's viscoelastic response to LGM deglaciation. We modelled rock uplift by reconstructing the Alpine ice cap, while accounting for postglacial erosion, sediment deposition and spatial variations in lithospheric rigidity. Clusters of excessive uplift in the Rhône Valley and in the Eastern Alps delineate regions potentially affected by mantle processes, crustal heterogeneity and active tectonics. Our study shows that even small LGM ice caps can dominate present-day rock uplift in tectonically active regions.

Perchlorate Found by Phoenix Could Provide a Mobile Brine Sludge at the Bed of Mars Northern Ice Cap that Would Allow Flow with Very Low Basal Temperatures: Possible Mechanism for Water Table Re-Charge

NASA Astrophysics Data System (ADS)

Fisher, D. A.; Hecht, M.; Kounaves, S.; Catling, D.

2009-03-01

The north cap of Mars has basal temperature that precludes the flow of ice. Phoenix discovered polar soils contain perchlorate salts. These salts depress the melting point so it could form a sludge that provides a mobile bed that moves the ice outwards.

Surface elevation change on ice caps in the Qaanaaq region, northwestern Greenland

NASA Astrophysics Data System (ADS)

Saito, Jun; Sugiyama, Shin; Tsutaki, Shun; Sawagaki, Takanobu

2016-09-01

A large number of glaciers and ice caps (GICs) are distributed along the Greenland coast, physically separated from the ice sheet. The total area of these GICs accounts for 5% of Greenland's ice cover. Melt water input from the GICs to the ocean substantially contributed to sea-level rise over the last century. Here, we report surface elevation changes of six ice caps near Qaanaaq (77°28‧N, 69°13‧W) in northwestern Greenland based on photogrammetric analysis of stereo pair satellite images. We processed the images with a digital map plotting instrument to generate digital elevation models (DEMs) in 2006 and 2010 with a grid resolution of 500 m. Generated DEMs were compared to measure surface elevation changes between 2006 and 2010. Over the study area of the six ice caps, covering 1215 km2, the mean rate of elevation change was -1.1 ± 0.1 m a-1. This rate is significantly greater than that previously reported for the 2003-2008 period (-0.6 ± 0.1 m a-1) for GICs all of northwestern Greenland. This increased mass loss is consistent with the rise in summer temperatures in this region at a rate of 0.12 °C a-1 for the 1997-2013 period.

H2O grain size and the amount of dust in Mars' residual north polar cap

NASA Technical Reports Server (NTRS)

Kieffer, Hugh H.

1990-01-01

In Mars' north polar cap, the probable composition of material residual from the annual condensation cycle is a mixture of fine dust and H2O grains of comparable size and abundance. However, metamorphism of such material will gradually lower its albedo by increasing the size of the H2O grains only. If the cap is undergoing net annual sublimation (as inferred from water vapor observations), late summer observations should be of old ice with H2O grain sizes of 100 microns or more. Ice of this granularity containing 30 percent fine dust has a reflectivity similar to that of dust alone; the observed albedo and computed ice grain size imply dust concentrations of 1 part per 1000 or less. The brightness of the icy areas conflicts with what would be expected for a residual cap deposited by an annual cycle similar to that observed by Viking and aged for thousands of years. The residual cap surface cannot be 'old dirty' ice. It could be old, coarse, and clean; or it could be young, fine, and dirty. This brings into question both the source of the late summer water vapor and the formation rate of laminated terrain.

H2O grain size and the amount of dust in Mars' residual North polar cap

USGS Publications Warehouse

Kieffer, H.H.

1990-01-01

In Mars' north polar cap the probable composition of material residual from the annual condensation cycle is a mixture of fine dust and H2O grains of comparable size and abundance. However, metamorphism of such material will gradually lower its albedo by increasing the size of the H2O grains only. If the cap is undergoing net annual sublimation (as inferred from water vapor observations), late summer observations should be of old ice with H2O grain sizes of 100 ??m or more. Ice of this granularity containing 30% fine dust has a reflectivity similar to that of dust alone; the observed albedo and computed ice grain size imply dust concentrations of 1 part per 1000 or less. The brightness of the icy areas conflicts with what would be expected for a residual cap deposited by an annual cycle similar to that observed by Viking and aged for thousands of years. The residual cap surface cannot be "old dirty' ice. It could be old, coarse, and clean; or it could be young, fine, and dirty. This brings into question both the source of the late summer water vapor and the formation rate of laminated terrain. -Author

Comparison of Mars Northern Cap Edge Advance and Recession Rates over the Last 6 Mars Years

NASA Astrophysics Data System (ADS)

Titus, T. N.; Cushing, G. E.; Langevin, Y.; Brown, A. J.; Themis Science Team; CRISM Science Team

2011-12-01

The most observable parameter that describes the Mars polar seasonal caps is their size, which has been measured since the days of Herschel. The advance and retreat of the polar cap from year to year may exhibit many clues to help elucidate little understood physical processes. For example, summertime heat storage in the regolith could delay the onset of seasonal CO2 cap formation. The evolution of the seasonal cap could also be directly affected by the thermal inertia of the near-surface regolith and place constraints on the depth of the ice table. Parameterizations of the seasonal cap edges provide useful constraints on atmospheric GCMs and mesoscale models. Longitudinally resolving the cap edges as they advance and retreat constrains the times when zonal means are appropriate and when longitudinal asymmetries make zonal means invalid. These same kinds of parameterizations can also be used when modeling other data that have low spatial resolutions, such as Gamma Ray Spectrometer (GRS )and Neutron Spectrometer (NS) data. By knowing where the cap edge should be, coarse spatial data can correct for subpixel mixing caused by large point-spread functions including both frosted and frost-free areas. The northern cap exhibits a near symmetric retreat, which has been well characterized at visible wavelengths by both telescopic and spacecraft observations. However, the advance of the cap has not been well characterized until the 21st century. Kieffer and Titus (2001) have used zonal means to observe surface temperature and visible bolometric albedo variations with season using MGS/TES. The TES thermal observations show an almost perfectly symmetrical advance; i.e., condensation at consistent latitude across all longitudes, with the most northern edge of the seasonal cap occurring between longitudes 245°E to 265°E and the most southern edge of the seasonal cap occurring between 280°E and 30°E. The advance of the northern cap typically leads the advance of the edge of polar night by 10° of latitude. The northern spring retreat is also nearly symmetric in both visual and thermal observations, and follows the same small asymmetries as seen in the advance. In addition to four Mars years of seasonal observations by TES and MOC, the northern seasonal cap was observed in detail by OMEGA in 2004 and 2006. The bright ring at intermediate temperatures (~ 180 K) observed by TES (Kieffer and Titus, 2001) in early spring is confirmed by OMEGA as resulting from H2O ice frost, with a sublimation front which lags by up to 4° in latitude south of the CO2 ice sublimation front. H2O ice contamination of CO2 ice is ubiquitous in the northern seasonal cap at all stages of its evolution. H2O ice dominates the spectral signatures over most of the seasonal cap after mid-spring. This paper will compare the inter-annual variations in the advance and recession of the Mars northern polar cap over the last 6 Mars years using TES, THEMIS, OMEGA, and CRISM.

Seasonal Changes in Mars' North Polar Ice Cap

NASA Technical Reports Server (NTRS)

1997-01-01

These images, which seem to have been taken while NASA's Hubble Space Telescope (HST) was looking directly down on the Martian North Pole, were actually created by assembling mosaics of three sets of images taken by HST in October, 1996 and in January and March, 1997 and projecting them to appear as they would if seen from above the pole. This first mosaic is a view which could not actually be seen in nature because at this season a portion of the pole would have actually been in shadow; the last view, taken near the summer solstice, would correspond to the Midnight Sun on Earth with the pole fully illuminated all day. The resulting polar maps begin at 50 degrees N latitude and are oriented with 0 degrees longitude at the 12 o'clock position. This series of pictures captures the seasonal retreat of Mars' north polar cap.

October 1996 (early spring in the Northern hemisphere): In this map, assembled from images obtained between Oct. 8 and 15, the cap extends down to 60 degrees N latitude, nearly it's maximum winter extent. (The notches are areas where Hubble data were not available). A thin, comma-shaped cloud of dust can be seen as a salmon-colored crescent at the 7 o'clock position. The cap is actually fairly circular about the geographic pole at this season; the bluish 'knobs' where the cap seems to extend further are actually clouds that occurred near the edges of the three separate sets of images used to make the mosaic.

January 1997 (mid-spring): Increased warming as spring progresses in the northern hemisphere has sublimated the carbon dioxide ice and frost below 70 degrees north latitude. The faint darker circle inside the cap boundary marks the location of circumpolar sand dunes (see March '97 map); these dark dunes are warmed more by solar heating than are the brighter surroundings, so the surface frost sublimates from the dunes earlier than from the neighboring areas. Particularly evident is the marked hexagonal shape of the polar cap at this season, noted previously by HST in 1995 and Mariner 9 in 1972; this may be due to topography, which isn't well known, or to wave structure in the circulation. This map was assembled from WFPC2 images obtained between Dec. 30, 1996 and Jan. 4, 1997.

March 30, 1997 (early summer): The cap has fully retreated to its remnant core of water-ice. This residual cap is actually almost cut into two by a large, horn-shaped canyon called Chasma Borealis which is cut deeply into the polar terrain. The HST images also reveal a curious layered terrain which is evidence of past climatic changes on Mars. The sublimation of all of the carbon dioxide has exposed the ring of dark sand dunes which encircle the North Polar Cap. Outliers of ice persist south of the polar sand sea (between the 3 o'clock and 9 o'clock positions). The bright circular features at 3, 6, and 9 o'clock are ice-filled craters.

All images were taken with the Wide Field and Planetary Camera 2. The color is constructed from images taken in red (673 nm) , blue (410 nm) and green (502 nm) light. The resolution at the North Pole ranges from about 115 km/pixel in October '96 to about 45 km/pixel in March '97.

This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/pubinfo/

High LMD GCM Resolution Modeling of the Seasonal Evolution of the Martian Northern Permanent Cap: Comparison with Mars Express OMEGA Observations

NASA Technical Reports Server (NTRS)

Levrard, B.; Forget, F.; Montmessin, F.; Schmitt, B.; Doute, S.; Langevin, Y.; Poulet, F.; Bibring, J. P.; Gondet, B.

2005-01-01

Analyses of imaging data from Mariner, Viking and MGS have shown that surface properties (albedo, temperature) of the northern cap present significant differences within the summer season and between Mars years. These observations include differential brightening and/or darkening between polar areas from the end of the spring to midsummer. These differences are attributed to changes in grain size or dust content of surface ice. To better understand the summer behavior of the permanent northern polar cap, we perfomed a high resolution modeling (approximately 1 deg x 1 deg.) of northern cap in the Martian Climate/water cycle as simulated by the Laboratoire de Meteorologie Dynamique (LMD) global climate model. We compare the predicted properties of the surface ice (ice thickness, temperature) with the Mars Express Omega summer observations of the northern cap. albedo and thermal inertia svariations model. In particular, albedo variations could be constrained by OMEGA data. Meteorological predictions of the LMD GCM wil be presented at the conference to interpret the unprecedently resolved OMEGA observations. The specific evolution of regions of interest (cap center, Chasma Boreal...) and the possibility of late summer global cap brightening will be discussed.

Holocene glacier variability and Neoglacial hydroclimate at Ålfotbreen, western Norway

NASA Astrophysics Data System (ADS)

Gjerde, Marthe; Bakke, Jostein; Vasskog, Kristian; Nesje, Atle; Hormes, Anne

2016-02-01

Glaciers and small ice caps respond rapidly to climate perturbations (mainly winter precipitation, and summer temperature), and the mass-balance of glaciers located in western Norway is governed mainly by winter precipitation (Pw). Records of past Pw can offer important insight into long-term changes in atmospheric circulation, but few proxies are able to accurately capture winter climate variations in Scandinavia. Reconstructions of equilibrium-line-altitude (ELA) variations from glaciers that are sensitive to changes in Pw therefore provide a unique opportunity to quantify past winter climate in this region. Here we present a new, Holocene glacier activity reconstruction for the maritime ice cap Ålfotbreen in western Norway, based on investigations of distal glacier-fed lake sediments and modern mass balance measurements (1963-2010). Several lake sediment cores have been subject to a suite of laboratory analyses, including measurements of physical parameters such as dry bulk density (DBD) and loss-on-ignition (LOI), geochemistry (XRF), surface magnetic susceptibility (MS), and grain size distribution, to identify glacial sedimentation in the lake. Both radiocarbon (AMS 14C) and 210Pb dating were applied to establish age-depth relationships in the sediment cores. A novel approach was used to calibrate the sedimentary record against a simple ELA model, which allowed reconstruction of continuous ELA changes for Ålfotbreen during the Neoglacial (when Ålfotbreen was present, i.e. the last ∼1400 years). Furthermore, the resulting ELA variations were combined with an independent summer temperature record to calculate Neoglacial Pw using the 'Liestøl equation'. The resulting Pw record is of higher resolution than previous reconstructions from glaciers in Norway and shows the potential of glacier records to provide high-resolution data reflecting past variations in hydroclimate. Complete deglaciation of the Ålfotbreen occurred ∼9700 cal yr BP, and the ice cap was subsequently absent or very small until a short-lived glacier event is seen in the lake sediments ∼8200 cal yr BP. The ice cap was most likely completely melted until a new glacier event occurred around ∼5300 cal yr BP, coeval with the onset of the Neoglacial at several other glaciers in southwestern Norway. Ålfotbreen was thereafter absent (or very small) until the onset of the Neoglacial period ∼1400 cal yr BP. The 'Little Ice Age' (LIA) ∼650-50 cal yr BP was the largest glacier advance of Ålfotbreen since deglaciation, with a maximum extent at ∼400-200 cal yr BP, when the ELA was lowered approximately 200 m relative to today. The late onset of the Neoglacial at Ålfotbreen is suggested to be a result of its low altitude relative to the regional ELA. A synthesis of Neoglacial ELA fluctuations along the coast of Norway indicates a time-transgressive trend in the maximum extent of the LIA, which apparently seems to have occurred progressively later as we move northwards. We suggest that this trend is likely due to regional winter precipitation differences along the coast of Norway.

Thermal infrared and visual observations of a water ice lag in the Mars southern summer

USGS Publications Warehouse

Titus, T.N.

2005-01-01

We present thermal infrared and visual evidence for the existence of water ice lags in the early southern summer. The observed H2O-ice lags lay in and near a chasma and appears to survive between 6-8 sols past the sublimation of the CO2. Possible sources of the H2O that compose the lag are (1) atmospheric H2O that is incorporated into the seasonal cap during condensation, (2) cold trapping of atmospheric water vapor onto the surface of the cap in the spring, or (3) a combination of the 2 processes where water is released from the sublimating cap only to be transported back over the cap edge and cold trapped. We refer to this later process as the "Houben" effect which may enrich the amount of water contained in the seasonal cap at 85??S by as much as a factor of 15. This phenomenon, which has already been identified for the northern retreating cap, may present an important water transport mechanism in the Southern Hemisphere.

Reconciling different observations of the CO2 ice mass loading of the Martian north polar cap

USGS Publications Warehouse

Haberle, R.M.; Mattingly, B.; Titus, T.N.

2004-01-01

The GRS measurements of the peak mass loading of the north polar CO2 ice cap on Mars are about 60% lower than those calculated from MGS TES radiation data and those inferred from the MOLA cap thicknesses. However, the GRS data provide the most accurate measurement of the mass loading. We show that the TES and MOLA data can be reconciled with the GRS data if (1) subsurface heat conduction and atmospheric heat transport are included in the TES mass budget calculations, and (2) the density of the polar deposits is ???600 kg m-3. The latter is much less than that expected for slab ice (???1600 kg m-3) and suggests that processes unique to the north polar region are responsible for the low cap density. Copyright 2004 by the American Geophysical Union.

ExoMars Lander Radioscience LaRa, a Space Geodesy Experiment to Mars.

NASA Astrophysics Data System (ADS)

Dehant, V.; Le Maistre, S.; Baland, R. M.; Yseboodt, M.; Peters, M. J.; Karatekin, O.; Rivoldini, A.; Van Hoolst, T.

2017-09-01

The LaRa (Lander Radioscience) experiment is designed to obtain coherent two-way Doppler measurements from the radio link between the ExoMars lander and Earth over at least one Martian year. The Doppler measurements will be used to observe the orientation and rotation of Mars in space (precession, nutations, and length-of-day variations), as well as polar motion. The ultimate objective is to obtain information / constraints on the Martian interior, and on the sublimation / condensation cycle of atmospheric CO2. Rotational variations will allow us to constrain the moment of inertia of the entire planet, including its mantle and core, the moment of inertia of the core, and seasonal mass transfer between the atmosphere and the ice caps.

Continuous profiles of microstructure, stable water isotopes and impurity content of the 2m snow pack from three polar drill sites

NASA Astrophysics Data System (ADS)

Freitag, Johannes; Schaller, Christoph; Kipfstuhl, Sepp; Hörhold, Maria; Schaidt, Maximilian; Sander, Merle; Moser, Dorothea

2017-04-01

Interpreting polar ice as climate archive requires profound knowledge about the formation of climate-proxies within the upper snow column. In order to investigate different impact factors on signal formation we performed a multiproxy- approach for 2m deep snow profiles by continuously measuring the 3D-microstructure using core-scale X-CT and the isotopic composition and impurity load in discrete samples of 1.1cm spatial resolution. The study includes profiles from a low-accumulation site on the East Antarctic plateau (Kohnen Station, DML), a typical medium-accumulation site on the North-East-Greenland ice sheet (EGRIP drilling camp) and a high-accumulation site on the Renland ice cap (East-coast of Greenland, RECAP drilling camp). Major observations are the tooth-shaped imprint of structural anisotropy and sulfate concentrations at the low accumulation site, the clear isotopic inter-annual variations that are in line with distinct impurity peaks at the high-accumulation site and the unexpected missing footprint of ice crusts and refrozen melt layers within the impurity- and isotope records for all sites.

Breaking the Ice Between Reporters and Scientists During IPY

NASA Astrophysics Data System (ADS)

Bentley, M.

2007-12-01

Communicating scientific information to the general public is a challenge. If the story's not about health advice, a major breakthrough or a natural disaster, scientists may be left wondering how to capture the public's attention and convey the importance of their research. This is a particular challenge in the International Polar Year in which the relevant research has global impacts, but is more nuanced than the headline-grabbing threat of melting ice caps. For example, as ANDRILL punches through ice, it's rock the scientists are after. What can a rock core tell us about how ice comes and goes, and what kind of drill can penetrate 20 million years of strata anyway? In this talk, I will describe how scientists can help communicate to journalists - and thereby the public - the importance of polar research, and give examples of how to help make their work compelling and accessible to those outside of a particular circle of expertise. I will use my experience reporting on science and climate change for the BBC to discuss what frustrations journalists have when talking to scientists and what scientists find difficult in talking to reporters.

North Polar Cap

NASA Technical Reports Server (NTRS)

2004-01-01

7 September 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a 1.4 m/pixel (5 ft/pixel) view of a typical martian north polar ice cap texture. The surface is pitted and rough at the scale of several meters. The north polar residual cap of Mars consists mainly of water ice, while the south polar residual cap is mostly carbon dioxide. This picture is located near 85.2oN, 283.2oW. The image covers an area approximately 1 km wide by 1.4 km high (0.62 by 0.87 miles). Sunlight illuminates this scene from the lower left.

Characterization of Mars' seasonal caps using neutron spectroscopy

USGS Publications Warehouse

Prettyman, T.H.; Feldman, W.C.; Titus, T.N.

2009-01-01

Mars' seasonal caps are characterized during Mars years 26 and 27 (April 2002 to January 2006) using data acquired by the 2001 Mars Odyssey Neutron Spectrometer. Time-dependent maps of the column abundance of seasonal CO 2 surface ice poleward of 60?? latitude in both hemispheres are determined from spatially deconvolved, epithermal neutron counting data. Sources of systematic error are analyzed, including spatial blurring by the spectrometer's broad footprint and the seasonal variations in the abundance of noncondensable gas at high southern latitudes, which are found to be consistent with results reported by Sprague et al. (2004, 2007). Corrections for spatial blurring are found to be important during the recession, when the column abundance of seasonal CO2 ice has the largest latitude gradient. The measured distribution and inventory of seasonal CO2 ice is compared to simulations by a general circulation model (GCM) calibrated using Viking lander pressure data, cap edge functions determined by thermal emission spectroscopy, and other nuclear spectroscopy data sets. On the basis of the amount of CO2 cycled through the caps during years 26 and 27, the gross polar energy balance has not changed significantly since Viking. The distribution of seasonal CO2 ice is longitudinally asymmetric: in the north, deposition rates of CO2 ice are elevated in Acidalia, which is exposed to katabatic winds from Chasma Borealis; in the south, CO2 deposition is highest near the residual cap. During southern recession, CO 2 ice is present longer than calculated by the GCM, which has implications for the local polar energy balance. Copyright 2009 by the American Geophysical Union.

On the possibility of ice on Greenland during the Eocene-Oligocene transition

NASA Astrophysics Data System (ADS)

Langebroek, Petra M.; Nisancioglu, Kerim H.; Lunt, Daniel J.; Kathrine Pedersen, Vivi; Nele Meckler, A.; Gasson, Edward

2017-04-01

The Eocene-Oligocene transition ( 34 Ma) is one of the major climate transitions of the Cenozoic era. Atmospheric CO2 decreased from the high levels of the Greenhouse world (>1000 ppm) to values of about 600-700 ppm in the early Oligocene. High latitude temperatures dropped by several degrees, causing a large-scale expansion of the Antarctic ice sheet. Concurrently, in the Northern Hemisphere, the inception of ice caps on Greenland is suggested by indirect evidence from ice-rafted debris and changes in erosional regime. However, ice sheet models have not been able to simulate extensive ice on Greenland under the warm climate of the Eocene-Oligocene transition. We show that elevated bedrock topography is key in solving this inconsistency. During the late Eocene / early Oligocene, East Greenland bedrock elevations were likely higher than today due to tectonic and deep-Earth processes related to the break-up of the North Atlantic and the position of the Icelandic plume. When allowing for higher initial bedrock topography, we do simulate a large ice cap on Greenland under the still relatively warm climate of the early Oligocene. Ice inception takes place at high elevations in the colder regions of North and Northeast Greenland; with the size of the ice cap being strongly dependent on the climate forcing and the bedrock topography applied.

Exposed water ice discovered near the south pole of Mars

USGS Publications Warehouse

Titus, T.N.; Kieffer, H.H.; Christensen, P.R.

2003-01-01

The Mars Odyssey Thermal Emission Imaging System (THEMIS) has discovered water ice exposed near the edge of Mars' southern perennial polar cap. The surface H2O ice was first observed by THEMIS as a region that was cooler than expected for dry soil at that latitude during the summer season. Diurnal and seasonal temperature trends derived from Mars Global Surveyor Thermal Emission Spectrometer observations indicate that there is H2O ice at the surface. Viking observations, and the few other relevant THEMIS observations, indicate that surface H2O ice may be widespread around and under the perennial CO2 cap.

A comprehensive interpretation of the NEEM basal ice build-up using a multi-parametric approach

NASA Astrophysics Data System (ADS)

Goossens, Thomas; Sapart, Célia J.; Dahl-Jensen, Dorthe; Popp, Trevor; El Amri, Saïda; Tison, Jean-Louis

2016-03-01

Basal ice is a common expression to describe bottom ice layers of glaciers, ice caps and ice sheets in which the ice is primarily conditioned by processes operating at the bed. It is chemically and/or physically distinct from the ice above and can be characterized by a component of basally derived sediments. The study of basal ice properties provides a rare opportunity to improve our understanding of subglacial environments and processes and to refine ice sheet behaviour modelling. Here, we present and discuss the results of water stable isotopes (δ18O and δD), ice fabrics, debris weight/size distribution and gas content of the basal part of the NEEM (North Greenland Eemian Ice Drilling Project) ice core. Below a depth of 2533.85 m, almost 10 m of basal debris-rich material was retrieved from the borehole, and regular occurrence of frozen sediments with only interstitial ice lenses in the bottom 5 m suggest that the ice-bedrock interface was reached. The sequence is composed of an alternation of three visually contrasting types of ice: clear ice with specks (very small amounts) of particulate inclusions, stratified debris-rich layers and ice containing dispersed debris. The use of water stable isotope signatures (δ18O and δD), together with other parameters, allows discrimination between the different types of ice and to unravel the processes involved in their formation and transformation. The basal debris-rich material presents δ18O values [-39.9 ‰; -34.4 ‰] within the range of the above last 300 m of unaltered meteoric ice [-44.9 ‰; -30.6 ‰] spanning a glacial-interglacial range of values. This rules out the hypothesis of a basal ice layer originating from pre-ice sheet ice overridden by the growing ice sheet, as previously suggested e.g. in the case of GRIP (Greenland Ice Core Project). We show that clear basal ice with specks corresponds to altered meteoric glacial ice where some of the climatic signal could have been preserved. However, the stratified debris-rich layers and the ice containing dispersed debris layers respectively express an "open" or "closed" system melting/refreezing signature, somewhat blurred by mixing processes in the upper part of the sequence. Climatic reconstruction is therefore prohibited from these ice types. We propose a first interpretative framework for the build-up of the NEEM basal ice sequence, based on the origin of the various ice types.

Initial Insights into the Quaternary Evolution of the Laurentide Ice Sheet on Southeastern Baffin Island

NASA Astrophysics Data System (ADS)

Pendleton, S.; Anderson, R. S.; Miller, G. H.; Refsnider, K. A.

2015-12-01

Increasing Arctic summer temperatures in recent decades and shrinking cold-based ice caps on Cumberland Peninsula, Baffin Island, are exposing ancient landscapes complete with uneroded bedrock surfaces. Previous work has indicated that these upland surfaces covered with cold-based ice experience negligible erosion compared with the valleys and fjords systems that contain fast-flowing ice. Given the appearance of highly weathered bedrock, it is argued that these landscapes have remained largely unchanged since at least the last interglaciation (~120 ka), and have likely experienced multiple cycles of ice expansion and retraction with little erosion throughout the Quaternary. To explore this hypothesis, we use multiple cosmogenic radionuclides (26Al and 10Be) to investigate and provide insight into longer-term cryosphere activity and landscape evolution. 26Al/10Be in surfaces recently exposed exhibit a wide range of exposure-burial histories. Total exposure-burial times range from ~0.3 - 1.5 My and estimated erosion rates from 0.5 - 6.2 m Ma-1. The upland surfaces of the Penny Ice cap generally experienced higher erosion rates (~0.45 cm ka-1) than those covered by smaller ice caps (~0.2 cm ka-1). The cumulative burial/exposure histories in high, fjord-edge locations indicate that significant erosion north of the Penny Ice Cap ceased between ~600 and 800 ka, suggesting that Laurentide Ice Sheet (LIS) organization and fjord inception was underway by at least this time. Additionally, 26Al/10Be ratios near production values despite high inventories from a coastal summit 50 km east of the Penny Ice Cape suggest that that area has not experienced appreciable burial by ice, suggesting that it was never inundated by the LIS. Moreover, these initial data suggest a variable and dynamic cryosphere in the region and provide insight into how large ice sheets evolved and organized themselves during the Quaternary.

Insect-Based Holocene (and Last Interglacial?) Paleothermometry from the E and NW Greenland Ice Sheet Margins: A Fly's-Eye View of Warmth on Greenland

NASA Astrophysics Data System (ADS)

Axford, Y.; Bigl, M.; Carrio, C.; Corbett, L. B.; Francis, D. R.; Hall, B. L.; Kelly, M. A.; Levy, L.; Lowell, T. V.; Osterberg, E. C.; Richter, N.; Roy, E.; Schellinger, G. C.

2013-12-01

Here we present new paleotemperature reconstructions based upon insect (Chironomidae) assemblages and other proxies from lake sediment cores recovered in east Greenland at ~71° N near Scoresby Sund and in northwest Greenland at ~77° N near Thule/Qaanaaq. In east Greenland, Last Chance Lake (informal name) is a small, non-glacial lake situated ~90 km east of the Greenland Ice Sheet margin. The lake preserves a sedimentary record of the entire Holocene (Levy et al. 2013). Chironomids from Last Chance Lake record cold summer temperatures (and establishment of a cold-climate fauna including abundant Oliveridia and Pseudodiamesa) during the late Holocene, preceded by summer temperatures estimated to have been 3 to 6°C warmer during the first half of the Holocene (when summer insolation forcing was greater than today). In northwest Greenland, Delta Sø and Wax Lips Lake (informal name) both preserve Holocene sediments. Here we discuss the late Holocene chironomid record from Delta Sø, whereas from Wax Lips Lake (a small, non-glacial lake situated ~2 km west of the ice sheet margin) we present a longer sedimentary and biostratigraphic record. The deeper portions of cores from Wax Lips Lake yield pre-Holocene and nonfinite radiocarbon ages, suggesting that this lake preserves sediments predating the Last Glacial Maximum. Abundant chironomids in the pre-glacial sediments appear to record interglacial conditions, and we infer that these sediments may date to the Last Interglacial (Eemian). The preservation of in situ Last Interglacial lacustrine sediments so close to the modern ice sheet margin suggests a minimally erosive glacierization style throughout the last glacial period, like that inferred for other Arctic locales such as on Baffin Island (Briner et al. 2007), ~750 km southwest of our study site. Our study sites are situated nearby key ice core sites (including NEEM, Camp Century, Agassiz and Renland) and very close to the ice sheet margin. These chironomid records therefore provide opportunities to compare climate inferences based upon ice core data and reconstructed ice margin histories with independent, biologically based estimates of air temperatures for the Holocene and possibly the Last Interglacial. Briner, J.P., Axford, Y., Forman, S.L., Miller, G.H., and Wolfe, A.P. 2007. Multiple generations of interglacial lake sediment preserved beneath the Laurentide Ice Sheet. Geology 35, 887-890. Levy, L.B., Kelly, M.A., Lowell, T.V., Hall, B.L., Hempel, L.A., Honsaker, W.M., Lusas, A.R., Howley, J.A., Axford, Y.L., 2013. Holocene fluctuations of Bregne ice cap, Scoresby Sund, east Greenland: a proxy for climate along the Greenland Ice Sheet margin. In press, Quaternary Science Reviews.

Insect-Based Holocene (and Last Interglacial?) Paleothermometry from the E and NW Greenland Ice Sheet Margins: A Fly's-Eye View of Warmth on Greenland

NASA Astrophysics Data System (ADS)

Axford, Y.; Bigl, M.; Carrio, C.; Corbett, L. B.; Francis, D. R.; Hall, B. L.; Kelly, M. A.; Levy, L.; Lowell, T. V.; Osterberg, E. C.; Richter, N.; Roy, E.; Schellinger, G. C.

2011-12-01

Here we present new paleotemperature reconstructions based upon insect (Chironomidae) assemblages and other proxies from lake sediment cores recovered in east Greenland at ~71° N near Scoresby Sund and in northwest Greenland at ~77° N near Thule/Qaanaaq. In east Greenland, Last Chance Lake (informal name) is a small, non-glacial lake situated ~90 km east of the Greenland Ice Sheet margin. The lake preserves a sedimentary record of the entire Holocene (Levy et al. 2013). Chironomids from Last Chance Lake record cold summer temperatures (and establishment of a cold-climate fauna including abundant Oliveridia and Pseudodiamesa) during the late Holocene, preceded by summer temperatures estimated to have been 3 to 6°C warmer during the first half of the Holocene (when summer insolation forcing was greater than today). In northwest Greenland, Delta Sø and Wax Lips Lake (informal name) both preserve Holocene sediments. Here we discuss the late Holocene chironomid record from Delta Sø, whereas from Wax Lips Lake (a small, non-glacial lake situated ~2 km west of the ice sheet margin) we present a longer sedimentary and biostratigraphic record. The deeper portions of cores from Wax Lips Lake yield pre-Holocene and nonfinite radiocarbon ages, suggesting that this lake preserves sediments predating the Last Glacial Maximum. Abundant chironomids in the pre-glacial sediments appear to record interglacial conditions, and we infer that these sediments may date to the Last Interglacial (Eemian). The preservation of in situ Last Interglacial lacustrine sediments so close to the modern ice sheet margin suggests a minimally erosive glacierization style throughout the last glacial period, like that inferred for other Arctic locales such as on Baffin Island (Briner et al. 2007), ~750 km southwest of our study site. Our study sites are situated nearby key ice core sites (including NEEM, Camp Century, Agassiz and Renland) and very close to the ice sheet margin. These chironomid records therefore provide opportunities to compare climate inferences based upon ice core data and reconstructed ice margin histories with independent, biologically based estimates of air temperatures for the Holocene and possibly the Last Interglacial. Briner, J.P., Axford, Y., Forman, S.L., Miller, G.H., and Wolfe, A.P. 2007. Multiple generations of interglacial lake sediment preserved beneath the Laurentide Ice Sheet. Geology 35, 887-890. Levy, L.B., Kelly, M.A., Lowell, T.V., Hall, B.L., Hempel, L.A., Honsaker, W.M., Lusas, A.R., Howley, J.A., Axford, Y.L., 2013. Holocene fluctuations of Bregne ice cap, Scoresby Sund, east Greenland: a proxy for climate along the Greenland Ice Sheet margin. In press, Quaternary Science Reviews.

Geochronology and paleoclimatic implications of the last deglaciation of the Mauna Kea Ice Cap, Hawaii

USGS Publications Warehouse

Anslow, Faron S.; Clark, P.U.; Kurz, M.D.; Hostetler, S.W.

2010-01-01

We present new 3He surface exposure ages on moraines and bedrock near the summit of Mauna Kea, Hawaii, which refine the age of the Mauna Kea Ice Cap during the Local Last Glacial Maximum (LLGM) and identify a subsequent fluctuation of the ice margin. The 3He ages, when combined with those reported previously, indicate that the local ice-cap margin began to retreat from its LLGM extent at 20.5??2.5ka, in agreement with the age of deglaciation determined from LLGM moraines elsewhere in the tropics. The ice-cap margin receded to a position at least 3km upslope for ~4.5-5.0kyr before readvancing nearly to its LLGM extent. The timing of this readvance at ~15.4ka corresponds to a large reduction of the Atlantic meridional overturning circulation (AMOC) following Heinrich Event 1. Subsequent ice-margin retreat began at 14.6??1.9ka, corresponding to a rapid resumption of the AMOC and onset of the B??lling warm interval, with the ice cap melting rapidly to complete deglaciation. Additional 3He ages obtained from a flood deposit date the catastrophic outburst of a moraine-dammed lake roughly coeval with the Younger Dryas cold interval, suggesting a more active hydrological cycle on Mauna Kea at this time. A coupled mass balance and ice dynamics model is used to constrain the climate required to generate ice caps of LLGM and readvance sizes. The depression of the LLGM equilibrium line altitude requires atmospheric cooling of 4.5??1??C, whereas the mass balance modeling indicates an accompanying increase in precipitation of as much as three times that of present. We hypothesize (1) that the LLGM temperature depression was associated with global cooling, (2) that the temperature depression that contributed to the readvance occurred in response to an atmospheric teleconnection to the North Atlantic, and (3) that the precipitation enhancement associated with both events occurred in response to a southward shift in the position of the inter-tropical convergence zone (ITCZ). Such a shift in the ITCZ would have allowed midlatitude cyclones to reach Mauna Kea more frequently which would have increased precipitation at high elevations and caused additional cooling. ?? 2010 Elsevier B.V.

Interglacial Greenland aerosol deposition: comparison of continuous high resolution chemical ice core records from the Eemian and Holocene

NASA Astrophysics Data System (ADS)

Gfeller, Gideon; Bigler, Matthias; Schüpbach, Simon; Mini, Olivia; Leuenberger, Daiana; Fischer, Hubertus

2014-05-01

Earth's climate system has been oscillating over the last million years between cold glacials and warm interglacials, leaving the imprints of their climate states in form of isotopes variations and chemical impurities in polar ice caps. In the course of the North Greenland Eemian Ice Drilling (NEEM) project, the NEEM ice core has been entirely analysed in very high depth resolution with a Continuous Flow Analysis (CFA) system for the concentrations of chemical aerosol tracers in the ice. Only in the brittle ice zone (600-1100 m depth equivalent to the time interval 3000-8000 years before present) most of the ice had to be discarded due to multifractured core material. Based on the unique reconstructed age scale to unfold the stratigraphically disturbed part from about 2200 m depth downwards (NEEM community members, Nature, 2013), we are able to present the first Greenland chemistry record over the entire last interglacial, the so called Eemian period (about 128'000 to 115'000 years ago). As the Eemian is believed to have been 4 to 8 degrees C warmer than the modern climate, it can be used as an analogue for our present warming climate and, thus, contributes to a better understanding of processes causing natural variations. By means of the chemistry records we are able to assess the natural variability of Greenland Eemian climate and gain insight in its biogeochemical state. Here, short-term variability as well as long term trends of soluble chemical impurities in the Eemian are investigated and compared with those in the Holocene. Changes of organic processes in soils and biomass burning for example are assessed through soluble ammonium and nitrate concentrations. In comparison to the Holocene, ammonium concentrations were about 25% higher during the Eemian. Nitrate, on the other hand, shows about 25% lower concentrations. Sodium concentrations, reflecting changes in sea salt aerosol, are about 35% lower during the Eemian than during the Holocene. Calcium, generally regarded as a long range transport proxy, shows similar concentration during both periods.

Evidence for smaller extents of the northwestern Greenland Ice Sheet and North Ice Cap during the Holocene

NASA Astrophysics Data System (ADS)

Kelly, M. A.; Osterberg, E. C.; Axford, Y.; Bigl, M.; Birkel, S. D.; Corbett, L. B.; Roy, E. P.; Thompson, J. T.; Whitecloud, S.

2013-12-01

The Greenland Ice Sheet (GrIS) and local glaciers on Greenland are responding dynamically to warming temperatures with widespread retreat. GRACE satellite data (e.g., Kahn et al., 2010) and the Petermann Glacier calving events document the recent expansion of ice loss into northwestern Greenland. To improve the ability to estimate future ice loss in a warming climate, we are developing records of the response of the northwestern Greenlandic cryosphere to Holocene climatic conditions, with a focus on past warm periods. Our ongoing research includes analyses of glacial geology, sub-fossil vegetation, lake sediment cores, chironomid assemblages and ice cores combined with glaciological modeling. To constrain past ice extents that were as small as, or smaller than, at present, we recovered sub-fossil vegetation exposed at the receding margins of the GrIS and North Ice Cap (NIC) in the Nunatarssuaq region (~76.7°N, 67.4°W) and of the GrIS near Thule (~76.5°N, 68.7°W). We present vegetation types and radiocarbon ages of 30 plant samples collected in August 2012. In the Nunatarssuaq region, five ages of in situ (rooted) vegetation including Polytrichum moss, Saxifraga nathorstii and grasses located <5 m outboard of the GrIS margin are ~120-200 cal yr BP (range of medians of the 2-sigma calibrated age ranges). Nine ages of in situ Polytrichum, Saxifraga oppositafolia and grasses from ~1-5 m inboard of the NIC margin (excavated from beneath ice) range from ~50 to 310 cal yr BP. The growth of these plants occurred when the GrIS and NIC were at least as small as at present and their ages suggest that ice advances occurred in the last 50-120 yrs. In addition to the in situ samples, we collected plants from well-preserved ground material exposed along shear planes in the GrIS margins. In Nunatarssuaq, two Polytrichum mosses rooted in ground material and exposed along a shear plane in the GrIS margin date to 4680 and 4730 cal yr BP. Near Thule, three ages of Salix arctica rooted in ground material and exposed along a shear plane in the GrIS are ~170-390 cal yr BP. Four ages of plant fragments within ice in a shear plane in the NIC margin are ~600-950 cal yr BP. Since these organic remains have been transported from beneath the GrIS and NIC, respectively, they indicate times of smaller than present ice extents. Together these plants provide evidence that the northwestern GrIS was smaller than at present at ~4600-4800 and ~170-390 cal yr BP. Advance to the modern GrIS extent was likely underway at of after ~170 cal yr BP. NIC was smaller than at present at ~600-950 cal yr. Our ongoing research is investigating the climatic conditions during these times and the relationship of these restricted ice extents to those documented elsewhere on Greenland as well as on Baffin Island.

Tracking Retreat of the North Seasonal Ice Cap on Mars: Results from the THEMIS Investigation

NASA Technical Reports Server (NTRS)

Ivanov, A. B.; Wagstaff, K. L.; Ttus, T. N.

2005-01-01

The CO2 ice caps on Mars advance and retreat with the seasons. This phenomenon was first observed by Cassini and then confirmed by numerous ground based observations in 19th and 20th centuries. With the advent of the space age observations of the seasonal ice cap were done by all orbiting spacecraft starting with Mariner 7. Viking Orbiters and more recently the Mars Global Surveyor (particularly Mars Orbiter Camera (MOC) and Thermal Emission Spectrometer (TES) instruments) have accumulated significant data on the retreat of the CO2 seasonal cap. During Mars year 2 of THEMIS operations at Mars, we planned an observational campaign in which the THEMIS instrument (onboard the Mars Odyssey spacecraft) repeatedly observed the north seasonal polar cap from midwinter to late spring. THEMIS allows simultaneous observations in both Thermal IR (12.57 m) and Visible wavelengths (0.65 m). One of the goals for this work is to initiate an interannual program for observations of the seasonal ice caps using the THEMIS instrument. The most efficient way to detect the edge between frost and bare ground is directly onboard of the spacecraft. Prior to onboard software design effort, we have developed two groundbased algorithms for automatically finding the edge of the seasonal polar cap in THEMIS IR data. The first algorithm relies on fully calibrated data and can be used for highly reliable groundbased analyses. The second method was specifically developed for processing raw, uncalibrated data in a highly efficient way. It has the potential to enable automatic, onboard detections of the seasonal cap retreat. We have experimentally confirmed that both methods produce similar results, and we have validated both methods against a model constructed from the MGS TES data from the same season.

The influence of topographic feedback on a coupled mass balance and ice-flow model for Vestfonna ice-cap, Svalbard

NASA Astrophysics Data System (ADS)

Schäfer, Martina; Möller, Marco; Zwinger, Thomas; Moore, John

2016-04-01

Using a coupled simulation set-up between a by statistical climate data forced and to ice-cap resolution downscaled mass balance model and an ice-dynamic model, we study coupling effects for the Vestfonna ice cap, Nordaustlandet, Svalbard, by analysing the impacts of different imposed coupling intervals on mass-balance and sea-level rise (SLR) projections. Based on a method to estimate errors introduced by different coupling schemes, we find that neglecting the topographic feedback in the coupling leads to underestimations of 10-20% in SLR projections on century time-scales in our model compared to full coupling (i.e., exchange of properties using smallest occurring time-step). Using the same method it also is shown that parametrising mass-balance adjustment for changes in topography using lapse rates is a - in computational terms - cost-effective reasonably accurate alternative applied to an ice-cap like Vestfonna. We test the forcing imposed by different emission pathways (RCP 2.4, 4.5, 6.0 and 8.5). For most of them, over the time-period explored (2000-2100), fast-flowing outlet glaciers decrease in impacting SLR due to their deceleration and reduced mass flux as they thin and retreat from the coast, hence detaching from the ocean and thereby losing their major mass drainage mechanism, i.e., calving.

Evaluation of remote-sensing techniques to measure decadal-scale changes of Hofsjokull ice cap, Iceland

USGS Publications Warehouse

Hall, D.K.; Williams, R.S.; Barton, J.S.; Sigurdsson, O.; Smith, L.C.; Garvin, J.B.

2000-01-01

Dynamic surficial changes and changes in the position of the firn line and the areal extent of Hofsjökull ice cap, Iceland, were studied through analysis of a time series (1973–98) of synthetic-aperture radar (SAR) and Landsat data. A digital elevation model of Hofsjökull, which was constructed using SAR interferometry, was used to plot the SAR backscatter coefficient (σ°) vs elevation and air temperature along transects across the ice cap. Seasonal and daily σ° patterns are caused by freezing or thawing of the ice-cap surface, and abrupt changes in σ° are noted when the air temperature ranges from ∼−5° to 0°C. Late-summer 1997 σ° (SAR) and reflectance (Landsat) boundaries agree and appear to be coincident with the firn line and a SAR σ° boundary that can be seen in the January 1998 SAR image. In January 1994 through 1998, the elevation of this σ° boundary on the ice capwas quite stable, ranging from 1000 to 1300 m, while the equilibrium-line altitude, as measured on the ground, varied considerably. Thus the equilibrium line may be obscured by firn from previous years. Techniques are established to measure long-term changes in the elevation of the firn line and changes in the position of the ice margin.

Spider Web Pattern

NASA Technical Reports Server (NTRS)

2006-01-01

A delicate pattern, like that of a spider web, appears on top of the Mars residual polar cap, after the seasonal carbon-dioxide ice slab has disappeared. Next spring, these will likely mark the sites of vents when the carbon-dioxide ice cap returns. This Mars Global Surveyor, Mars Orbiter Camera image is about 3-kilometers wide (2-miles).

The Search for Subsurface Ice Caps on Mercury

NASA Astrophysics Data System (ADS)

Allen, R. A.; Barlow, N. G.; Vilas, F.

1996-03-01

Recent ground-based radar observations of Mercury have detected strong, highly depolarized echoes from the north and south polar regions which have been interpreted as possible polar ice deposits. These radar echoes have been correlated with a number of impact craters. Theoretical studies indicate that such surface ice can be stable within permanently shadowed areas, such as the floors of high latitude impact craters. One proposed hypothesis suggests that stable subsurface ice caps exist at the poles of Mercury, and that several of the impact events that created the high latitude craters exposed this subsurface ice. Thus, our study focused on the possibility of ice caps extending below the mercurian surface, down to some unknown latitude in the polar regions. We used the experiences from Mars, where the depth/diameter ratio (d/D) is smaller for ice rich areas, to investigate whether a comparable latitudinal change in d/D is detectable on Mercury. We found no significant latitudinal differences within the two polar regions of our study or between the north polar and equatorial quadrangles, but craters in the south polar region tend to have slightly lower d/D than those in the north polar region.

The role of mineral dust aerosols in polar amplification

NASA Astrophysics Data System (ADS)

Lambert, F.; Kug, J.; Park, R.; Jin, F.; Lee, J. H.

2010-12-01

During today’s global warming, as well as during glacial-interglacial changes, temperature increase is larger in polar areas than the global average, a phenomenon called “polar amplification”. Model studies suggest ice cap melting due to greenhouse gas induced temperature rise, and consequent decrease of albedo and enhanced oceanic and atmospheric heat transport, as the primary cause for this phenomenon in nowadays Arctic. However, the underlying causes for polar amplification on glacial-interglacial timescales are still unclear, especially in the Antarctic where sea ice coverage does not change as drastically as in the North. Recent results have shown that the temperature increase is not limited to the surface and that these changes can not be explained by snow and ice changes alone. Starting with dust flux measurements from ice cores in Greenland and Antarctica, we have estimated tropospheric concentrations using deposition velocities and vertical concentration profiles for Holocene and LGM conditions from the National Center for Atmospheric Research’s Community Climate System Model (CCSM3) and a 3-D global chemical transport model (GEOS-Chem). The radiative forcing due to mineral dust aerosols was then estimated using the GEOS-Chem model, based on the particle properties found in the ice. Preliminary results point towards positive forcing of dust because of the high albedo of the underlying ice sheets.

Possible recent and ancient glacial ice flow in the south polar region of Mars

NASA Technical Reports Server (NTRS)

Kargel, J. S.

1992-01-01

Martian polar science began almost as soon as small telescopes were trained on the planet. The seasonal expansion and contraction of the polar caps and their high albedoes led most astronomers to think that water ice is the dominant constituent. In 1911 Lowell perceived a bluish band around the retreating edge of the polar caps, and interpreted it as water from melting polar ice and seasonal snow. An alternative idea in his time was that the polar caps consist of frozen carbonic acid. Lowell rejected the carbonic acid hypothesis on account of his blue band. He also pointed out that carbonic acid would sublimate rather than melt at confining pressures near and below one bar, hence, carbonic acid could not account for the blue band. In comparing Lowell's theories with today's knowledge, it is recognized that (1) sublimation is mainly responsible for the growth and contraction of Mars' polar caps, (2) carbon dioxide is a major component of the southern polar cap, and (3) Lowell's blue band was probably seasonal dust and/or clouds. Geomorphic evidence that glacial ice and glacial melt waters once flowed over broad areas of the southern polar region. Two aspects of the south polar region suggest possible glacial processes during two distinct eras in Mars' history.

Improved parameterization of marine ice dynamics and flow instabilities for simulation of the Austfonna ice cap using a large-scale ice sheet model

NASA Astrophysics Data System (ADS)

Dunse, T.; Greve, R.; Schuler, T.; Hagen, J. M.; Navarro, F.; Vasilenko, E.; Reijmer, C.

2009-12-01

The Austfonna ice cap covers an area of 8120 km2 and is by far the largest glacier on Svalbard. Almost 30% of the entire area is grounded below sea-level, while the figure is as large as 57% for the known surge-type basins in particular. Marine ice dynamics, as well as flow instabilities presumably control flow regime, form and evolution of Austfonna. These issues are our focus in numerical simulations of the ice cap. We employ the thermodynamic, large-scale ice sheet model SICOPOLIS (http://sicopolis.greveweb.net/) which is based on the shallow-ice approximation. We present improved parameterizations of (a) the marine extent and calving and (b) processes that may initiate flow instabilities such as switches from cold to temperate basal conditions, surface steepening and hence, increases in driving stress, enhanced sliding or deformation of unconsolidated marine sediments and diminishing ice thicknesses towards flotation thickness. Space-borne interferometric snapshots of Austfonna revealed a velocity structure of a slow moving polar ice cap (< 10m/a) interrupted by distinct fast flow units with velocities in excess of 100m/a. However, observations of flow variability are scarce. In spring 2008, we established a series of stakes along the centrelines of two fast-flowing units. Repeated DGPS and continuous GPS measurements of the stake positions give insight in the temporal flow variability of these units and provide constrains to the modeled surface velocity field. Austfonna’s thermal structure is described as polythermal. However, direct measurements of the temperature distribution is available only from one single borehole at the summit area. The vertical temperature profile shows that the bulk of the 567m thick ice column is cold, only underlain by a thin temperate basal layer of approximately 20m. To acquire a spatially extended picture of the thermal structure (and bed topography), we used low-frequency (20 MHz) GPR profiling across the ice cap and the particular flow units. The measurements indicate that the gross volume of Austfonna is cold. This observation is supported by model results which suggest that regional fast flow occurs despite the lack of considerable temperate-ice volumes. This in turn indicates that fast flow is accomplished exclusively by basal motion in regions where the glacier base is at pressure-melting conditions, and not by enhanced deformation of considerable volumes of temperate ice.

Holocene Paleolimnological Records from Thule, Northwestern Greenland

NASA Astrophysics Data System (ADS)

Corbett, L.; Osterberg, E. C.; Kelly, M. A.; Axford, Y.

2012-12-01

Assessing Holocene climatic and environmental variability around the margin of the Greenland Ice Sheet provides important information against which to compare ice sheet margin fluctuations. Here, we report preliminary results from ongoing research in northwestern Greenland. We present records of physical properties of lake sediments and use these to make inferences about the evolution of the lake and its surroundings over the latter half of the Holocene. We collected two sediment cores, 90 and 72 cm in length, from a small (surface area ~0.3 km2), shallow (maximum depth ~4.5 m) lake at 76°33'40''N 68°26'31''W near Thule Air Base in July 2012. The length of the cores was limited by the length of the core barrel and does not reflect the total thickness of sediment in the lake. The lake is situated within the glacial limit and likely formed subsequent to deglaciation of the region during early Holocene time. No glaciers exist within the lake's catchment today; the primary modern source of sediment is a perennial inflow from the west. We developed a preliminary depth-age model using radiocarbon ages of terrestrial organic macrofossils. Thus far, we have analyzed the sediments for magnetic susceptibility and loss-on-ignition. A radiocarbon age of 6069 ± 90 cal yr BP at the base of the core indicates that the sediments preserve a continuous record of middle to late Holocene conditions. The top of both cores consists of a thick (~12 cm) layer of dark gray unlaminated sediments, while the rest of the material in both cores is lighter brown to olive, finely laminated sediment. The upper layer is characterized by low water content (<25%), low loss-on-ignition (<5%), and high magnetic susceptibility (~150-250 x10-6). Conversely, the laminated sediments beneath have higher water content (~40-50%), higher loss-on-ignition (~5-10%), and much lower magnetic susceptibility (<50 x10-6). We hypothesize that the upper, less organic unit may represent a single event in the lake's recent history. We are refining the depth-age model with more radiocarbon ages, measuring grain size and carbon to nitrogen ratios of the sediments, and evaluating possible linkages between the sediment physical properties and precipitation as recorded by annual accumulation in ice cores in northwestern Greenland and Arctic Canada. This project will provide a foundation for future work in Thule investigating Holocene fluctuations of local ice cap and ice sheet margin positions.

Exploring Arctic history through scientific drilling

NASA Astrophysics Data System (ADS)

ODP Leg 151 Shipboard Scientific Party

During the brief Arctic summer of 1993, the Ocean Drilling Program's research vessel JOIDES Resolution recovered the first scientific drill cores from the eastern Arctic Ocean. Dodging rafts of pack ice shed from the Arctic ice cap, the science party sampled sediments north of 80°N latitude from the Yermak Plateau, as well as from sites in Fram Strait, the northeastern Greenland margin, and the Iceland Plateau (Figure 1).The sediments collected reveal the earliest history of the connection between the North Atlantic and Arctic Oceans through the Nordic Seas. The region between Greenland and Norway first formed a series of isolated basins, sometimes with restricted deep circulation, that eventually joined and allowed deep and surface Arctic Ocean water to invade the region. A record was also retrieved that shows major glaciation in the region began about 2.5 m.y.a.

Long-distance relationship between large-scale tropical SSTs and ice core-derived oxygen isotopic records in the Third Pole Region

NASA Astrophysics Data System (ADS)

Thompson, L. G.; Yao, T.; Mosley-Thompson, E. S.; Lin, P.

2012-12-01

The tropical hydrological cycle is a key factor coupling isotopic records from ice core, speleothem and lake records with tropical SSTs and the vertical amplification of temperature in the Tropics. Stable isotopic ratios, particularly of oxygen, preserved in glacier ice provide high resolution records of climate changes over long time periods. In polar ice sheets the isotopic signal is driven primarily by temperature while in low-latitudes it depends on a variety of hydrologic and thermal influences in the broad geographic region that supplies moisture to the mountain glaciers. The strong correlation between ice core-derived isotopic records throughout the low- and mid-latitudes and tropical SSTs likely reflects the dominance of tropical evaporation in the flux of water vapor to the atmosphere and provides a possible explanation for the large-scale isotopic links among low- and mid-latitude paleoclimate records. Many low- to mid-latitude ice fields provide continuous, annually-resolved proxy records of climatic and environmental variability recorded by many preserved and measurable parameters including oxygen and hydrogen isotopic ratios and net mass balance (accumulation). These records present an opportunity to examine the nature of climate variability in these regions in greater detail and to extract new information about long-distance relationships in the climate system. Understanding these relationships is essential for proper interpretation of the isotopic records archived in glaciers, lakes, speleothems and other paleo-archives in the Third Pole (TP) Region. Here we compare high resolution records from Dasuopu Glacier in the Himalaya, a speleothem record from Wanxiang Cave in Gansu Province on the TP and the annually resolved ice core records from the Quelccaya Ice Cap in the tropical Andes of South America. The purpose is to explore the role of long-distance processes in determining the isotopic composition of paleo archives on the TP. Running correlations between the Quelccaya and Dasuopu records over the last 500 years reveal that through time isotopes and net balance are both positively and negatively correlated over multi-decades scales while correlation of the annual values over the entire period is quite low. The annual isotopic records are strongly correlated with tropical Pacific SSTs (R2 = 0.55) reflecting the strong linkage between tropical Pacific SSTs associated with ENSO and tropospheric temperatures in the low latitudes. The well-documented contemporaneous loss of ice cover on Quelccaya, Naimona'nyi, Kilimanjaro in eastern Africa and the ice fields near Puncak Jaya in Papua, Indonesia likely reflects the dominance of large-scale processes. Moreover, such widespread melting is consistent with model predictions for a vertical amplification of temperature in the tropics and with increasing isotopic enrichment with elevation across the Third Pole Region over the last 100 years.

Transitions between multiple equilibria of paleo climate: a glimpse in to the dynamics of abrupt climate change

NASA Astrophysics Data System (ADS)

Ferreira, David; Marshall, John; Ito, Takamitsu; McGee, David; Moreno-Chamarro, Eduardo

2017-04-01

The dynamics regulating large climatic transitions such as glacial-interglacial cycles or DO events remains a puzzle. Forcings behind these transitions are not robustly identified and potential candidates (e.g. Milankovitch cycles, freshwater perturbations) often appear too weak to explain such dramatic transitions. A potential solution to this long-standing puzzle is that Earth's climate is endowed with multiple equilibrium states of global extent. Such states are commonly found in low-order or conceptual climate models, but it is unclear whether a system as complex as Earth's climate can sustain multiple equilibrium states. Here we report that multiple equilibrium states of the climate system are also possible in a complex, fully dynamical coupled ocean-atmosphere-sea ice GCM with idealized Earth-like geometry, resolved weather systems and a hydrological cycle. In our model, two equilibrium states coexist for the same parameters and external forcings: a Warm climate with a small Northern hemisphere sea ice cap and a large southern one and a Cold climate with large ice caps at both poles. The dynamical states of the Warm and Cold solutions exhibit striking similarities with our present-day climate and the climate of the Last Glacial Maximum, respectively. A carbon cycle model driven by the two dynamical states produces an atmospheric pCO2 draw-down of about 110 pm between the Warm and Cold states, close to Glacial-Interglacial differences found in ice cores. Mechanism controlling the existence of the multiple states and changes in the atmospheric CO2 will be briefly presented. Finally we willdescribe transition experiments from the Cold to the Warm state, focusing on the lead-lags in the system, notably between the Northern and Southern Hemispheres climates.

Sub-Antarctic glacier extensions in the Kerguelen region (49°S, Indian Ocean) over the past 24,000 years constrained by 36Cl moraine dating

NASA Astrophysics Data System (ADS)

Jomelli, Vincent; Mokadem, Fatima; Schimmelpfennig, Irene; Chapron, Emmanuel; Rinterknecht, Vincent; Favier, Vincent; Verfaillie, Deborah; Brunstein, Daniel; Legentil, Claude; Michel, Elisabeth; Swingedouw, Didier; Jaouen, Alain; Aumaitre, Georges; Bourlès, Didier L.; Keddadouche, Karim

2017-04-01

Similar to many other regions in the world, glaciers in the southern sub-polar regions are currently retreating. In the Kerguelen Islands (49°S, 69°E), the mass balance of the Cook Ice Cap (CIC), the largest ice cap in this region, experienced dramatic shrinking between 1960 and 2013 with retreat rates among the highest in the world. This observation needs to be evaluated in a long-term context. However, data on the past glacier extents are sparse in the sub-Antarctic regions. To investigate the deglaciation pattern since the Last Glacial Maximum (LGM) period, we present the first 13 cosmogenic 36Cl surface exposure ages from four sites in the Kerguelen Islands. The 36Cl ages from erratic and moraine boulders span from 24.4 ± 2.7 ka to 0.3 ± 0.1 ka. We combined these ages with existing glacio-marine radiocarbon ages and bathymetric data to document the temporal and spatial changes of the island's glacial history. Ice began to retreat on the main island before 24.4 ± 2.7 ka until around the time of the Antarctic Cold Reversal (ACR) period (∼14.5-12.9 ka), during which the Bontemps moraine was formed by the advance of a CIC outlet glacier. Deglaciation continued during the Holocene probably until 3 ka with evidence of minor advances during the last millennium. This chronology is in pace with major changes in δ18O in a recent West Antarctica ice core record, showing that Kerguelen Islands glaciers are particularly sensitive and relevant to document climate change in the southern polar regions.

Perspective of Life Search in Martian Econiches

NASA Astrophysics Data System (ADS)

Demidov, N. E.

2017-05-01

Mars may be divided on five ecological niches according to presence and state of water: permanent polar caps, dry regolith, subpermafrost aquifers, cryopegs and ice containing regolith. Basic limiting factors for the search of life in this econiches are: absence of water (dry regolith), depth of burial (cryopegs and subpermafrost aquifers), age (ice containing permafrost and polar caps). High priority targets for the search of life on Mars are represented by permanently frozen deposits of young polar volcanoes and ash layers in polar caps. During volcanic eruptions microorganisms from subpermafrost aquifers could propagate to the surface and survive in permafrost or ice for million years, as it is known to happen on Earth. Possibility of specific lithic habitats in dry layer must also be taken into account.

Characterizing near-surface firn from the scattered signal component of glacier surface reflections detected in airborne radio-echo sounding measurements

NASA Astrophysics Data System (ADS)

Rutishauser, A.; Grima, C.; Sharp, M. J.; Blankenship, D. D.; Young, D. A.; Cawkwell, F.; Dowdeswell, J. A.

2016-12-01

With recent summer warming, surface melt on Canadian Arctic ice caps has intensified and extended to higher elevations in ice cap accumulation areas. Consequently, more meltwater percolates into the near-surface firn, and refreezes as ice layers where firn temperatures are below freezing. This process can increase firn densification rates, causing a lowering of the glacier surface height even in the absence of mass changes. Thus, knowledge of spatio-temporal variations in the near-surface firn stratigraphy is important for interpreting altimetrically-derived estimates of ice cap mass balance. We investigate the use of the scattering signal component of glacier surface reflections in airborne radio-echo sounding (RES) measurements to characterize the near-surface firn stratigraphy. The scattering signal distribution over Devon Ice Cap is compared to firn stratigraphy derived from ground-based radar data. We identify three distinct firn facies zones at different elevation ranges. The scattered signal component changes significantly between the different firn facies zones: low scattering correlates to laterally homogeneous firn containing thin, flat and continuous ice layers at elevations above 1800 m and below 1200 m, where firn consists mainly of ice. Higher scattering values are found from 1200-1800 m where the firn contains discrete, undulating ice layers. No correlation was found between the scattering component and surface roughness. Modelled scattering values for the measured roughness were significantly less than the observed values, and did not reproduce their observed spatial distribution. This indicates that the scattering component is determined mainly by the structure of near-surface firn. Our results suggest that the scattering component of surface reflections from airborne RES measurements has potential for characterizing heterogeneity in the spatial structure of firn that is affected by melting and refreezing processes.

Short-term variations of Icelandic ice cap mass inferred from cGPS coordinate time series

NASA Astrophysics Data System (ADS)

Compton, Kathleen; Bennett, Richard A.; Hreinsdóttir, Sigrún; van Dam, Tonie; Bordoni, Andrea; Barletta, Valentina; Spada, Giorgio

2017-06-01

As the global climate changes, understanding short-term variations in water storage is increasingly important. Continuously operating Global Positioning System (cGPS) stations in Iceland record annual periodic motion—the elastic response to winter accumulation and spring melt seasons—with peak-to-peak vertical amplitudes over 20 mm for those sites in the Central Highlands. Here for the first time for Iceland, we demonstrate the utility of these cGPS-measured displacements for estimating seasonal and shorter-term ice cap mass changes. We calculate unit responses to each of the five largest ice caps in central Iceland at each of the 62 cGPS locations using an elastic half-space model and estimate ice mass variations from the cGPS time series using a simple least squares inversion scheme. We utilize all three components of motion, taking advantage of the seasonal motion recorded in the horizontal. We remove secular velocities and accelerations and explore the impact that seasonal motions due to atmospheric, hydrologic, and nontidal ocean loading have on our inversion results. Our results match available summer and winter mass balance measurements well, and we reproduce the seasonal stake-based observations of loading and melting within the 1σ confidence bounds of the inversion. We identify nonperiodic ice mass changes associated with interannual variability in precipitation and other processes such as increased melting due to reduced ice surface albedo or decreased melting due to ice cap insulation in response to tephra deposition following volcanic eruptions, processes that are not resolved with once or twice-yearly stake measurements.

Surface Exposure Dating of the Huancané III Moraines in Peru: A Record of Quelccaya Ice Cap's Maximum Extent during the Last Glacial Period

NASA Astrophysics Data System (ADS)

Baranes, H. E.; Kelly, M. A.; Stroup, J. S.; Howley, J. A.; Lowell, T. V.

2012-12-01

The climatic conditions that influenced the tropics during the height of the last glacial period are not well defined and controversial. There are disparities in estimates of temperature anomalies (e.g., MARGO, 2009; Rind and Peteet, 1985; CLIMAP, 1976), and critical terrestrial paleotemperature proxy records in tropical regions are poorly dated (e.g., Porter, 2001). Defining these conditions is important for understanding the mechanisms that cause major shifts in climate, as the tropics are a primary driver of atmospheric and oceanic circulation. This study aims to constrain the timing of maximum glacier extents in the Cordillera Oriental in southern Peru during the last glacial period by applying surface exposure (beryllium-10) dating to the Huancané III (Hu-III) moraines. The Hu-III moraines mark the maximum extent of Quelccaya Ice Cap (QIC) (13.93°S, 70.83°W), the largest tropical ice cap, during the last ice age. The eight beryllium-10 ages presented here yield 17,056 ± 520 yrs ago as a minimum age for the onset of recession from the ice cap advance marked by the Hu-III moraines. Comparing this age to other paleoclimate records indicates that the ice cap advance marked by the Hu-III moraines is more likely associated with a North Atlantic climate event known as Heinrich I (H1; 16,800 yrs ago, Bond et al., 1992, 1993) than with global cooling at the Last Glacial Maximum (LGM; ~21,000 yrs ago, Denton and Hughes, 1981). This result suggests that climate processes in the North Atlantic region are linked to climatic conditions in the tropical Andes. A mesoscale climate model and an ice-flow model are currently being developed for QIC. The moraine data presented in this study will be used with these two models to test response of QIC to North Atlantic and global climate events.

Arctic polynya and glacier interactions

NASA Astrophysics Data System (ADS)

Edwards, Laura

2013-04-01

Major uncertainties surround future estimates of sea level rise attributable to mass loss from the polar ice sheets and ice caps. Understanding changes across the Arctic is vital as major potential contributors to sea level, the Greenland Ice Sheet and the ice caps and glaciers of the Canadian Arctic archipelago, have experienced dramatic changes in recent times. Most ice mass loss is currently focused at a relatively small number of glacier catchments where ice acceleration, thinning and calving occurs at ocean margins. Research suggests that these tidewater glaciers accelerate and iceberg calving rates increase when warming ocean currents increase melt on the underside of floating glacier ice and when adjacent sea ice is removed causing a reduction in 'buttressing' back stress. Thus localised changes in ocean temperatures and in sea ice (extent and thickness) adjacent to major glacial catchments can impact hugely on the dynamics of, and hence mass lost from, terrestrial ice sheets and ice caps. Polynyas are areas of open water within sea ice which remain unfrozen for much of the year. They vary significantly in size (~3 km2 to > ~50,000 km2 in the Arctic), recurrence rates and duration. Despite their relatively small size, polynyas play a vital role in the heat balance of the polar oceans and strongly impact regional oceanography. Where polynyas develop adjacent to tidewater glaciers their influence on ocean circulation and water temperatures may play a major part in controlling subsurface ice melt rates by impacting on the water masses reaching the calving front. Areas of open water also play a significant role in controlling the potential of the atmosphere to carry moisture, as well as allowing heat exchange between the atmosphere and ocean, and so can influence accumulation on (and hence thickness of) glaciers and ice caps. Polynya presence and size also has implications for sea ice extent and therefore potentially the buttressing effect on neighbouring tidewater glaciers. The work presented discusses preliminary satellite observations of concurrent changes in the North Water and Nares Strait polynyas and neighbouring tidewater glaciers in Greenland and the Canadian Arctic where notable thinning and acceleration of glaciers have been observed. Also included is an outline of how these observations will fit into a much wider project on the topic involving ocean, atmosphere and sea ice modelling and short-term and longer-term in-situ measurements.

Observations of the northern seasonal polar cap on Mars: I. Spring sublimation activity and processes

USGS Publications Warehouse

Hansen, C.J.; Byrne, S.; Portyankina, G.; Bourke, M.; Dundas, C.; McEwen, A.; Mellon, M.; Pommerol, A.; Thomas, N.

2013-01-01

Spring sublimation of the seasonal CO2 northern polar cap is a dynamic process in the current Mars climate. Phenomena include dark fans of dune material propelled out onto the seasonal ice layer, polygonal cracks in the seasonal ice, sand flow down slipfaces, and outbreaks of gas and sand around the dune margins. These phenomena are concentrated on the north polar erg that encircles the northern residual polar cap. The Mars Reconnaissance Orbiter has been in orbit for three Mars years, allowing us to observe three northern spring seasons. Activity is consistent with and well described by the Kieffer model of basal sublimation of the seasonal layer of ice applied originally in the southern hemisphere. Three typical weak spots have been identified on the dunes for escape of gas sublimed from the bottom of the seasonal ice layer: the crest of the dune, the interface of the dune with the interdune substrate, and through polygonal cracks in the ice. Pressurized gas flows through these vents and carries out material entrained from the dune. Furrows in the dunes channel gas to outbreak points and may be the northern equivalent of southern radially-organized channels (“araneiform” terrain), albeit not permanent. Properties of the seasonal CO2 ice layer are derived from timing of seasonal events such as when final sublimation occurs. Modification of dune morphology shows that landscape evolution is occurring on Mars today, driven by seasonal activity associated with sublimation of the seasonal CO2 polar cap.

Interior structure and seasonal mass redistribution of Mars from radio tracking of Mars Pathfinder

NASA Technical Reports Server (NTRS)

Folkner, W. M.; Yoder, C. F.; Yuan, D. N.; Standish, E. M.; Preston, R. A.

1997-01-01

Doppler and range measurements to the Mars Pathfinder lander made using its radio communications system have been combined with similar measurements from the Viking landers to estimate improved values of the precession of Mars' pole of rotation and the variation in Mars' rotation rate. The observed precession of -7576 +/- 35 milliarc seconds of angle per year implies a dense core and constrains possible models of interior composition. The estimated annual variation in rotation is in good agreement with a model of seasonal mass exchange of carbon dioxide between the atmosphere and ice caps.

Interior structure and seasonal mass redistribution of Mars from radio tracking of Mars Pathfinder.

PubMed

Folkner, W M; Yoder, C F; Yuan, D N; Standish, E M; Preston, R A

1997-12-05

Doppler and range measurements to the Mars Pathfinder lander made using its radio communications system have been combined with similar measurements from the Viking landers to estimate improved values of the precession of Mars' pole of rotation and the variation in Mars' rotation rate. The observed precession of -7576 +/- 35 milliarc seconds of angle per year implies a dense core and constrains possible models of interior composition. The estimated annual variation in rotation is in good agreement with a model of seasonal mass exchange of carbon dioxide between the atmosphere and ice caps.

An examination of Mars' north seasonal polar cap using MGS: Composition and infrared radiation balance

NASA Astrophysics Data System (ADS)

Hansen, Gary B.

2013-08-01

A detailed analysis of data from one revolution of the Mars Global Surveyor (MGS) is presented. Approximately 80% of this revolution observes the mid-winter northern seasonal polar cap, which covers the surface to <60°N, and which is predominantly within polar night. The surface composition and temperature are determined through analysis of 6-50 μm infrared spectra from the Thermal Emission Spectrometer (TES). The infrared radiative balance, which is the entire heat balance in the polar night except for small subsurface and atmospheric advection terms, is calculated for the surface and atmospheric column. The primary constituent, CO2 ice, also dominates the infrared spectral properties by variations in its grain size and by admixtures of dust and water ice, which cause large variations in the 20-50 μm emissivity. This is modified by incomplete areal coverage, and clouds or hazes. This quantitative analysis reveals CO2 grain radii ranging from ˜100 μm in isolated areas, to 1-5 mm in more widespread regions. The water ice content varies from none to about one part per thousand by mass, with a clear increase towards the periphery of the polar cap. The dust content is typically a few parts per thousand by mass, but is as much as an order of magnitude less abundant in "cold spot" regions, where the low emissivity of pure CO2 ice is revealed. This is the first quantitative analysis of thermal spectra of the seasonal polar cap and the first to estimate water ice content. Our models show that the cold spots represent cleaner, dust-free ice rather than finer grained ice than the background. Our guess is that the dust in cold spots is hidden in the center of the CO2 frost particles rather than not present. The fringes of the cap have more dust and water ice, and become patchy, with warmer water snow filling the gaps on the night side, and warmer bare soil on the day side. A low optical depth (<1 in the visible) water ice atmospheric haze is apparent on the night side, and appears with smaller optical depth on the day side. The infrared radiative balance at the surface is typically 20-25 W m-2 in the central polar cap, with ˜25% dips in the regions of dust-free CO2. The atmospheric radiative terms are typically 1-3 W m-2.

WCRP's Climate and Cryosphere (CliC) Project: Climate Change and Middle and Low Latitude Glaciers

NASA Astrophysics Data System (ADS)

Dick, C. A.; Clic Project, W.

2004-12-01

The newest World Climate Research Programme (WCRP) Core Project, the Climate and Cryosphere (CliC) Project, is concerned with all aspects of the interactions between the cryosphere and climate. The cryosphere, defined as those portions of the Earth's surface where water exists in solid form, is an integral part of the climate system, both responding to, and influencing climate change. The cryosphere also provides many of the best indicators of climate variability and change. In addition to a range of direct physical indicators (e.g., snow/sea ice/glacier extent and thickness, river and lake freeze-up/break-up dates, etc.), ice cores from glaciers, ice caps and ice sheets have been shown to contain a wealth of information about past climate and environmental conditions. Ice cores are of particular value, since they often come from areas that are remote and poorly observed, yet have a major effect on the climate of the rest of the globe. General Circulation Models (GCMs) usually predict that the Earth's polar regions will warm fastest with the increasing levels of atmospheric greenhouse gases. However, models also indicate that continental interiors should warm more quickly than marine areas at non-polar latitudes. In fact, while some areas in the Arctic and Antarctic have warmed rapidly over the last few decades, it has generally been in the middle and low latitudes that the greatest effects of climate change have been observed. Particularly obvious has been the widespread retreat of glaciers. This retreat, and the warming which it implies, will have not only important scientific consequences but also socio-economic consequences in areas where glacier melt-water is an important component of the water supply. Glaciers preserve records of climate and the environment through both the isotopic composition of the water molecules, and through the chemicals 'trapped' in the snow, firn and ice layers. In polythermal (i.e., cold) glaciers where only limited melt occurs, the isotopic and chemical signals remain largely undisturbed, and ice cores can provide excellent high resolution records of past conditions. In temperate glaciers, where the ice is at its pressure melting point throughout, diffusion processes are much more rapid, and summer melt and run-off can drastically alter the chemical composition. Much of the climatic and environmental information is destroyed. This presentation will discuss the very serious concern that so many middle and low latitude glaciers are retreating and warming. The CliC Project recognizes an urgent need to recover ice cores from all non-polar glaciated regions before warming affects the glaciers and removes the information they contain. Without such information our ability to understand the climate changes that have occurred in the world's mountainous regions will be restricted, and our ability to model and predict future climate will be severely impaired.

Experimental investigation of insolation-driven dust ejection from Mars' CO2 ice caps

NASA Astrophysics Data System (ADS)

Kaufmann, E.; Hagermann, A.

2017-01-01

Mars' polar caps are - depending on hemisphere and season - partially or totally covered with CO2 ice. Icy surfaces such as the polar caps of Mars behave differently from surfaces covered with rock and soil when they are irradiated by solar light. The latter absorb and reflect incoming solar radiation within a thin layer beneath the surface. In contrast, ices are partially transparent in the visible spectral range and opaque in the infrared. Due to this fact, the solar radiation can penetrate to a certain depth and raise the temperature of the ice or dust below the surface. This may play an important role in the energy balance of icy surfaces in the solar system, as already noted in previous investigations. We investigated the temperature profiles inside CO2 ice samples including a dust layer under Martian conditions. We have been able to trigger dust eruptions, but also demonstrated that these require a very narrow range of temperature and ambient pressure. We discuss possible implications for the understanding of phenomena such as arachneiform patterns or fan shaped deposits as observed in Mars' southern polar region.

Last Glacial-Interglacial Transition ice dynamics in the Wicklow Mountains, Ireland

NASA Astrophysics Data System (ADS)

Knight, Lauren; Boston, Clare; Lovell, Harold; Pepin, Nick

2017-04-01

Understanding of the extent and dynamics of former ice masses in the Wicklow Mountains, Ireland, during the Last Glacial-Interglacial Transition (LGIT; 15-10 ka BP) is currently unresolved. Whilst it is acknowledged that the region hosted a local ice cap within the larger British-Irish Ice Sheet at the Last Glacial Maximum (LGM; 27 ka BP), there has been little consideration of ice cap disintegration to a topographically constrained ice mass during the LGIT. This research has produced the first regional glacial geomorphological map, through remote sensing (aerial photograph and digital terrain model interrogation) and field mapping. This has allowed both the style and extent of mountain glaciation and ice recession dynamics during the LGIT to be established. This geomorphological mapping has highlighted that evidence for local glaciation in the Wicklow Mountains is more extensive than previously recognised, and that small icefields and associated outlet valley glaciers existed during the LGIT following disintegration of the Wicklow Ice Cap. A relative chronology based on morphostratigraphic principles is developed, which indicates complex patterns of ice mass oscillation characterised by periods of both sustained retreat and minor readvance. Variations in the pattern of recession across the Wicklow Mountains are evident and appear to be influenced, in part, by topographic controls (e.g. slope, aspect, glacier hypsometry). In summary, this research establishes a relative chronology of glacial events in the region during the LGIT and presents constraints on ice mass extent, dynamics and retreat patterns, offering an insight into small ice mass behaviour in a warming climate.

Interpreting the Holocene fluctuations of Quelccaya Ice Cap, Peru: using a combination of glacial and non-glacial lake records

NASA Astrophysics Data System (ADS)

Stroup, J. S.; Kelly, M. A.; Lowell, T. V.; Smith, C.; Beal, S. A., Jr.; Tapia, P. M.

2016-12-01

The past fluctuations of Quelccaya Ice Cap (QIC) are an indicator of tropical paleoclimate. At QIC, ice core and glacial geological records provide late Holocene climate constraints. However, early and middle Holocene QIC fluctuations are less well-known. To interpret past QIC fluctuations, we present Holocene-long lake sediment records from Challpacocha, a lake fed by QIC meltwater, and Yanacocha, a lake that has not received meltwater during the Holocene. To assess the clastic sediment delivered to Challpacocha by QIC meltwater, we compare visual stratigraphy, X-ray fluorescence chemistry, grainsize, loss on ignition and clastic flux records from both lakes (additional Yanacocha proxies are presented by Axford et al. (this meeting, abstract 157985)). We compare the meltwater derived clastic sediment record from Challpacocha with moraine and stratigraphic records of past ice extents during the late Holocene. This comparison indicates that clastic sediment flux in Challpacocha increased during QIC recession and decreased during QIC advance, or significantly reduced QIC extent. We then use the Challpacocha clastic sediment record to interpret early and middle Holocene QIC fluctuations. Based on the Challpacocha sediment record, combined with prior work, we suggest that from 11 to 6.5 ka QIC was similar to or smaller than its late Holocene extent. From 6.9 to 6.5 ka QIC may have been absent from the landscape. At 3-2.4 and 0.62-0.31 ka QIC experienced the most extensive Holocene fluctuations. We compare the clastic sediment fluxes from Challpacocha and Pacococha (a nearby lake fed by QIC; Rodbell et al., 2008) to infer QIC expansion between 6.5-5 ka. This is supported by 14C ages of in-situ subfossil plants which indicate ice advance at 6.3-4.7 ka (Thompson et al., 2006, 2013; Buffen et al., 2009). Our study highlights the value of using multiple datasets to improve lake sediment record interpretations.

Paleoenvironmental changes during the past 2000 years, evidence from Kongsfjorden, Svalbard

NASA Astrophysics Data System (ADS)

Jernas, P.; Kristensen, D.; Koc, N.; Skirbekk, K.

2009-04-01

Over the past decades the Arctic has received more attention due to the rapid warming that is more pronounced there than elsewhere on the globe. Instrumental time series are too short to capture the range of natural variability in the Arctic and we therefore have to rely on proxy records to describe the whole range of natural variability. In this context the late-Holocene climate variations are particularly important because natural forcings and the Earth's boundary conditions have been approximately similar to those operating today. Documenting past natural climate variability has therefore a vital role to play in understanding the present climate and predicting future change. Here we present a high resolution marine record from Kongsfjorden covering the last c. 2000 years. The core site is located in Kongsfjorden situated on the western coast of Spitsbergen (Svalbard). We focus on this region because it lies along the path of inflow of warmer and saline subsurface waters via the West Spitsbergen Current which is one of the important heat sources for the Arctic Ocean. This current is a major regulator of environmental changes and for example sea-ice distribution in the west Svalbard area. Therefore quantification of it's spatially and temporally variations through time are essential for understanding past environmental and climate changes. We have investigated faunal variations in benthic foraminifera from the upper 60 cm (covering the last two millennia) of a gravity core (510 cm total length) sampled with one-cm density. Chronology of the gravity core is established by AMS radiocarbon dating. The core was in addition investigated for grain size analysis and x-ray. The sediment analysis and x-ray show the upper part of the core contains large amounts of IRD from 7 cm - 25 cm corresponding to an age of 150-700 cal yr. It indicates that abundant icebergs melted over the core site depositing IRD. Further down core (1000-1800 cal yr) there is a significant dominance of fine grained sediment and decrease in ice rafting indicating less influence from glaciers. The foraminiferal species composition show decreasing content of agglutinated foraminifera down core caused by their low preservation potential. For this core site it confirms the importance of calcareous foraminifera as a fossil record tool. The two dominant species in the core are Elphidium excavatum and Nonionellina labradorica. During the last 2000 years the percentage of E. excavatum shows a general tendency to decrease while N. labradorica increases toward present. Elphidium excavatum is typical for arctic glaciomarine environments close to glaciers and ice caps, indicating harsh conditions (cold bottom waters temperatures, lower salinity) and probably extensive ice cover. Nonionellina labradorica indicates the vicinity of oceanographic fronts and high productivity. Another species Islandiella spp., often associated with increased productivity and presence of the sea ice edge, shows significant increase in percentage from 1000 to 800 cal yr BP. From 600 to 400 cal yr BP Bucella spp. start to decline suggesting increased sea ice cover and diminished influence of the Coastal Current on the inner shelf of Svalbard.

Resident CAPS on dense-core vesicles docks and primes vesicles for fusion

PubMed Central

Kabachinski, Greg; Kielar-Grevstad, D. Michelle; Zhang, Xingmin; James, Declan J.; Martin, Thomas F. J.

2016-01-01

The Ca2+-dependent exocytosis of dense-core vesicles in neuroendocrine cells requires a priming step during which SNARE protein complexes assemble. CAPS (aka CADPS) is one of several factors required for vesicle priming; however, the localization and dynamics of CAPS at sites of exocytosis in live neuroendocrine cells has not been determined. We imaged CAPS before, during, and after single-vesicle fusion events in PC12 cells by TIRF micro­scopy. In addition to being a resident on cytoplasmic dense-core vesicles, CAPS was present in clusters of approximately nine molecules near the plasma membrane that corresponded to docked/tethered vesicles. CAPS accompanied vesicles to the plasma membrane and was present at all vesicle exocytic events. The knockdown of CAPS by shRNA eliminated the VAMP-2–dependent docking and evoked exocytosis of fusion-competent vesicles. A CAPS(ΔC135) protein that does not localize to vesicles failed to rescue vesicle docking and evoked exocytosis in CAPS-depleted cells, showing that CAPS residence on vesicles is essential. Our results indicate that dense-core vesicles carry CAPS to sites of exocytosis, where CAPS promotes vesicle docking and fusion competence, probably by initiating SNARE complex assembly. PMID:26700319

Regional Climate Modeling of Volcanic Eruptions and the Arctic Climate System: A Baffin Island Case Study

NASA Astrophysics Data System (ADS)

Losic, M.; Robock, A.

2010-12-01

It is well-understood that the effects of volcanic aerosol loading into the stratosphere are transient, with global cooling lasting only a few years after a single large eruption. Geological evidence collected from Northern Baffin Island, Canada, suggests ice cap growth began soon after a succession of several large eruptions in the 13th century, and they did not start to melt until roughly a century ago. We investigate which feedbacks allowed these ice caps to be maintained long after the transient forcing of the volcanic aerosols, by conducting sensitivity studies with the Weather Research and Forecasting (WRF) Model and Polar WRF, a version of WRF developed specifically for the polar regions. Results from an ensemble of month-long regional simulations over Baffin Island suggest that better treatment of snow and ice in Polar WRF improves our regional climate simulations. Thus, sensitivity test results from decade-long runs with imposed changes to boundary condition temperatures and carbon dioxide concentrations using Polar WRF are presented. Preliminary findings suggest that not only large scale but localized climate feedbacks play an important role in the responses of the ice caps after temperature and carbon dioxide forcings are applied. The results from these and further sensitivity tests will provide insight into the influence of regional feedbacks on the persistence of these ice caps long after the 13th century eruptions.

Low-latitude ice cores and freshwater availability

NASA Astrophysics Data System (ADS)

Kehrwald, Natalie Marie

2009-12-01

Recent retreat of Tibetan Plateau glaciers affects at least half a billion people. Himalayan glaciers seasonally release meltwater into tributaries of the Indus, Ganges, and Brahmaputra Rivers and supply freshwater necessary to support agricultural and economic practices. Tibetan Plateau glaciers are retreating more rapidly than mountain glaciers elsewhere in the world, and this retreat is accelerating. The Naimona'nyi (30°27'N; 81°91'E, 6050 m a.s.l), Guliya (35°17'N; 81°29'E, 6710 m a.s.l.) and Dasuopu (28°23'N; 85°43'E, 7200 m a.s.l.) ice cores place this recent retreat into a longer time perspective through quantifying climate parameters such as past temperature, aridity, and atmospheric chemistry. Naimona'nyi has not accumulated mass since at least 1950, as evidenced by the virtual lack of radiogenic isotopes (36Cl, 3 H, and beta radioactivity) present in the ice core. These isotopes were produced by U.S. and Soviet atmospheric thermonuclear bomb tests conducted in the 1950s and 1960s and provide independent dating horizons for the ice cores. Lead-210 dates imply that the uppermost preserved glacial ice on Naimona'nyi formed during the 1940s. While this is the highest documented glacial thinning in the world other glaciers at elevations similar to that of Naimona'nyi, such as Kilimanjaro (3°4'S; 37°21'E, 5893 m a.s.l.), are also losing mass at their summits. The global scope of high-elevation glacial thinning suggests that ablation on the Earth's highest ice fields may be more prevalent as global mean temperatures continue to increase. Glacial thinning has not been taken into account in future projections of regional freshwater availability, and the net mass loss indicates that Himalayan glaciers currently store less freshwater than assumed in models. The acceleration of Tibetan Plateau glacial retreat has been hypothesized to be due in part to deposition of black carbon (BC) from biomass burning on to ice fields, thereby lowering the reflectivity of the glacier surface and melting the upper ice. The application of a novel technique of measuring and radiocarbon-dating ultra-small samples (< 100mug) of the BC and total organic carbon (TOC) fractions of Naimona'nyi demonstrates a decrease (˜12 to 14 ka versus ˜7 ka) in the composite age of BC in the upper 40 m and lowest 20 m of the 137 m ice core, suggesting the incorporation of radiocarbon-dead BC. Precambrian black shale in the Lesser Himalaya provide a natural source material which may be operationally defined as black carbon and which may incorporate radiocarbon-dead sediments into the bulk 14C measurements, yet as the mean 14C age is ˜10 ka, modern BC from biomass burning must also be incorporated into the ice core record. While the uppermost sample (5 m) contains 38% BC, 210 Pb dates show that this depth corresponds to an age before 1850 AD, or before the regional Industrial Revolution. As BC is a hydrophobic substance, the BC is unlikely to have migrated through the firn and glacial ice. Therefore, the high-elevation thinning on Naimona'nyi appears to be a response to increased temperatures rather than primarily driven by changes in surface albedo. This technique was applied to the annually-dated ice core from the accumulating summit of the Quleccaya ice cap, Peru (13'56'S; 70°50'W; 5670 m a.s.l.). A marked increase in modern BC and TOC was measured since 1880 AD. No increase in radiocarbon-dead (> 60,000 ka) BC or TOC was noted, suggesting that the source of the carbon was from biomass burning, with a possible contribution of Amazon slash and burn clearing, rather than the input of fossil fuel combustion. The age of the BC and TOC is thousands of years older than the age of the surrounding ice, and should not be used to date the ice core. Although Naimona'nyi provides challenges for constructing an ice core chronology due to its lack of independent horizons such as volcanic activity, methane gas measurements, 14C dates, 3H, 36Cl, or beta radioactivity, the oxygen isotopic record can be correlated with the neighboring Dasuopu and Guliya ice cores. Naimona'nyi contains a pronounced positive ˜10‰ shift in delta18O in the basal 37 m of the core which mimics similar isotopic shifts in regional speleothems, lacustrian sediments, and planktonic foraminifera proxy records. This distinct shift is attributed to amplified monsoon intensity caused by increased summer insolation at 30°N. This correlation between regional proxy records results in a basal age of ˜8.6 ka for Naimona'nyi, suggesting that the ice field grew as a response to tropical rather than polar climate forcings.

Exploration of Antarctic Subglacial environments: a challenge for analytical chemistry

NASA Astrophysics Data System (ADS)

Traversi, R.; Becagli, S.; Castellano, E.; Ghedini, C.; Marino, F.; Rugi, F.; Severi, M.; Udisti, R.

2009-12-01

The large number of subglacial lakes detected in the Dome C area in East Antarctica suggests that this region may be a valuable source of paleo-records essential for understanding the evolution of the Antarctic ice cap and climate changes in the last several millions years. In the framework of the Project on “Exploration and characterization of Concordia Lake, Antarctica”, supported by Italian Program for Antarctic Research (PNRA), a glaciological investigation of the Dome C “Lake District” are planned. Indeed, the glacio-chemical characterisation of the ice column over subglacial lakes will allow to evaluate the fluxes of major and trace chemical species along the ice column and in the accreted ice and, consequently, the availability of nutrients and oligo-elements for possible biological activity in the lake water and sediments. Melting and freezing at the base of the ice sheet should be able to deliver carbon and salts to the lake, as observed for the Vostok subglacial lake, which are thought to be able to support a low concentration of micro-organisms for extended periods of time. Thus, this investigation represents the first step for exploring the subglacial environments including sampling and analysis of accreted ice, lake water and sediments. In order to perform reliable analytical measurements, especially of trace chemical species, clean sub-sampling and analytical techniques are required. For this purpose, the techniques already used by the CHIMPAC laboratory (Florence University) in the framework of international Antarctic drilling Projects (EPICA - European Project for Ice Coring in Antarctica, TALDICE - TALos Dome ICE core, ANDRILL MIS - ANTarctic DRILLing McMurdo Ice Shelf) were optimised and new techniques were developed to ensure a safe sample handling. CHIMPAC laboratory has been involved since several years in the study of Antarctic continent, primarily focused on understanding the bio-geo-chemical cycles of chemical markers and the interpretation of their records in sedimentary archives (ice cores, sediment cores). This activity takes advantage of facilities for storage, decontamination and pre-analysis treatment of ice and sediment strips (cold room equipped with laminar flow hoods and decontamination devices at different automation level, class 10000 clean room, systems for the complete acid digestion of sediment samples, production of ultra-pure acids and sediments’ granulometric selection) and for analytical determination of a wide range of chemical tracers. In particular, the operative instrumental set includes several Ion Chromatographs for inorganic and selected organic ions measurement (by classical Ion Chromatography and Fast Ion Chromatography), Atomic Absorption and Emission Spectrometers (F-AAS, GF-AAS, ICP-AES) and Inductively Coupled Plasma - Sector Field Mass Spectrometry (ICP-SFMS) for the analysis of the soluble or “available” inorganic fraction together with Ion Beam Analysis techniques for elemental composition (PIXE-PIGE, in collaboration with INFN and Physics Institute of Florence University) and geochemical analysis (SEM-EDS).

North-Polar Martian Cap as Habitat for Elementary Life

NASA Astrophysics Data System (ADS)

Wallis, M. K.; Wickramasinghe, J. T.; Wickramasinghe, N. C.

2008-09-01

North-polar cap over millenia Atmospheric water in Mars tends currently as for the past millenia to distil onto the polar caps and be buried under dust deposits. Diffusive release from ground-ice (and its excavation in meteorite impacts [1]) replenishes atmospheric water, allowing the gradual build up of polar ice-dust deposits. When sunlit, this warmed and sublimating ice-dust mix has interest as a potential habitat for micro-organisms. Modelling shows precipitable vapour at 10-50μm/yr, varying sensitively with small changes in orbitable obliquity around the present 25° [2]. The modelling applies to a globe with regionally uniform albedo, unlike the steep topography and dark layering of the north polar cap whose upper 300m have accumulated over the last 500 kyr [3]. The cliffs and ravines of the north-polar cap are thought to form through south-facing slopes sublimating and gaining a dirt-encrusted surface, while horizontal surfaces brighten through frost deposits. The two-phase surface derives from the dust and frost feedback on surface albedo [4] and the resulting terrain develops over diurnal cycles of frosting and sublimation, and over annual seasonal cycles. The steep south-facing sides of observed ravines when unshadowed would see for a few hours the full intensity of sunlight at near normal incidence, without the atmospheric dimming at similar inclinations on Earth. As exposed ice sublimates at T > 200K (partial pressure exceeds typical martian 0.1 Pa), a crust of dirt develops to maintain quasi-stability. The dirt crust's main function is to buffer the ice against diurnal temperature fluctuations, but it also slows down vapour diffusion - analogous to south polar ice sublimation [5] and the growth of ground-ice [6]. We envisage 1-10 mm/yr as the net sublimation rate, compatible with the 100 kyr life and scales of the north polar ravines. Modelling of icy-dirt crusts in the polar cap Plane-parallel layers have been used to model the changing temperature through the dirt-encrusted ice cliff [7]. Thermal conduction through the dirt crust limits sublimation of underlying ice. This allows use of the thermal wave solution: where the thermal diffusivity α combining conductivity and specific heat is taken constant and τ0 = 1.88 yr is the martian year. As in [6] we adopt a sinusoidal temperature variation and take α = 0.0001 m²/hour. Like the martian ground ice case, the transition from dirt to ice is quite sharp. The surface temperature variation at the polar cap determined from local radiative balance is largely determined by albedo, while sublimation losses from a south-facing cliff are concentrated in the summer months. For fresh frost, the albedo is close to unity but values 0.6-0.8 allow for varying amounts of exposed dirt or dust, as explored in Figure 1. This shows the integrated ice loss over one martian year (687 Earth days) using the thermal wave solution and the Clausius-Clapeyron equation for ice sublimation: for T in degrees Kelvin. The solutions in Fig. 1 indicate a 10-15cm dirt crust develops quite quickly, within a few decades, becoming thick enough to choke back the sublimation rate to under 1mm/yr, compatible with the age of the cliffs. Less steep slopes develop rather thinner crusts. The seasonal thermal wave of Equ.1 applies for depths exceeding ~5cm (two diurnal skin depths). For A of 0.6, Fig. 1 shows a 10 cm thick crust builds up in ~30yr; this thick a crust may plausibly be maintained against weathering processes. If A<0.5, the mean temperature is too high for thermal inertia alone to choke the sublimation; the crust thickens to >10 cm within a few years and the self-sealing (deposition) and flow-retarding (adsorption/desorption) properties become significant in the thicker and hotter crust [5]. For A>0.7, a 5 cm crust cuts the sublimation rate to <0.1 mm/yr - we expect frost deposition to dominate, keeping the surface icy with high albedo for most of the diurnal cycle. The thermal lag due to latent heat needs including for realistic modeling of the dirt-ice crust. Thus our parameterized exploration reveals a regime where sublimation is 10-100 times higher than precipitable water deposition, implying vapour pressures relatively favourable for ice-living microbes. Schorghofer's [2] modelling for horizontal nearpolar surfaces has ~30 cm deep soil that has filled with pore ice over the last 500 kyr. Environments for ice-based life Ice-dwelling micro-organisms found in the antarctic may be viable on Mars [8,9]. Ices generally have mobile water on internal surfaces of crystals and contaminants, which is presumed to facilitate diffusive transport of nutrients, enzymes and waste products, and to be available for cell processes. Species of archaea are found living in low-T ice. Data on methane in the GISP2 ice core and N2O in the Vostok core have been used [10] to infer there is no cut-off at T as low as -40oC and to derive an exp (-A/T) fit to data indicative of metabolic rates. We conceive that the dirt crusts formed on sublimating ice provide a habitat for psychrotrophic microbes. They reactivate metabolically under the midday warming pulse and take advantage of vapour from the underlying ice. On Mars like on comets, cmscale crusts would protect microbes from the harsh surface UV conditions. The extreme cold of the nightside and polar winter presents little problem to microbial spores and resting states. However, the ecological niches are isolated. We envisage that meteorite impacts on Mars mobilise material from these niches and disperse their micro-life around the planet. Meteorite impact cratering rates come from lunar data scaled to Mars, with account for the air decelerating and fragmenting small impacters [11]. This limits the power law to Δ > 10 m and gives a functional fit Ψ = 1.5 x 10-12 Δ-3.1 / km2.yr from Δ = 10 m to 100 m. (3) The volume integral of the excavated mass equates to an average `gardening' rate ~1 cm / Myr, dominated by the smallest craters ~ 0.3m deep. The craters are sparse on a Myr timescale, though secondary craters from excavated material surely contribute to mobilising cm-deep crusts. The formation and fragmentation of crusts that contained micro-organisms would contribute a biological component to martian soils in the polar regions, that could potentially reach the location of the Phoenix probe (at 68°N). One might expect these to be distinguishable via the onboard microscopy. References [1] Wallis M.K. (1995) Adv. Space Res. 15(4), 113-6. [2] Schorghofer N. (2007) Nature 449, 192-195. [3] Milkovich S.M., Head J.W., Neukum G. and the HRSC Co-Investigator Team (2008) Planet. Space Sci. 56, 266-288. [4] Pelletier J.D. (2004) Geology 32, 365-367 & 384. [5] Skorov Yu.V., Markiewicz W.J., Basilevsky A.T. and Keller H.U. (2001) Planet. Space Sci. 49, 59-63. [6] Schorghofer N. and Aharonson O. (2005) J.Geophys. Res., 110, E05003, 1-16. [7] Wallis M.K., Wickramasinghe N.C. and Wickramasinghe J.T. (2005) 5th EANA Workshop on Astrobiology, p.37, Budapest; Wickramasinghe J.T. (2007) The Role of Comets in Panspermia, Ph D. Thesis, Cardiff University [8] McKay C.P. (2003) Third Mars Polar Sci. Conf. 8056. [9] Hoover R.B., et al. (2004) in SPIE 5163, 191-202 (www.astrobiology.cf.ac.uk/SPIE2004.pdf). [10] Tung H.C., Bramhall N.E. & Price P.B. (2005) Proc. Nat. Acad. Sci. 102, 18292-18296. [11] Hartmann W.K. (2005) Icarus 174, 294-320.

Palmer Quest: A Feasible Nuclear Fission "Vision Mission" to the Mars Polar Caps

NASA Technical Reports Server (NTRS)

Carsey, F. D.; Beegle, L. W.; Nakagawa, R.; Elliott, J. O.; Matthews, J. B.; Coleman, M. L.; Hecht, M. H.; Ivaniov, A. B.; Head, J. W.; Milkovich, S.

2005-01-01

We are engaged in a NASA Vision Mission study, called Palmer Quest after the American Antarctic explorer Nathaniel Palmer, to assess the presence of life and evaluate the habitability of the basal domain of the Mars polar caps. We address this goal through four objectives: 1. Determine the presence of amino acids, nutrients, and geochemical heterogeneity in the ice sheet. 2. Quantify and characterize the provenance of the amino acids in Mars ice. 3. Assess the stratification of outcropped units for indications of habitable zones. 4. Determine the accumulation of ice, mineralogic material, and amino acids in Mars ice caps over the present epoch. Because of the defined scientific goal for the vision mission, the Palmer Quest focus is astrobiological; however, the results of the study make us optimistic that aggressive multi-platform in-situ missions that address a wide range of objectives, such as climate change, can be supported by variations of the approach used on this mission. Mission Overview: The Palmer Quest baseline

Leveraging Cloud Technology to Provide a Responsive, Reliable and Scalable Backend for the Virtual Ice Sheet Laboratory Using the Ice Sheet System Model and Amazon's Elastic Compute Cloud

NASA Astrophysics Data System (ADS)

Perez, G. L.; Larour, E. Y.; Halkides, D. J.; Cheng, D. L. C.

2015-12-01

The Virtual Ice Sheet Laboratory(VISL) is a Cryosphere outreach effort byscientists at the Jet Propulsion Laboratory(JPL) in Pasadena, CA, Earth and SpaceResearch(ESR) in Seattle, WA, and the University of California at Irvine (UCI), with the goal of providing interactive lessons for K-12 and college level students,while conforming to STEM guidelines. At the core of VISL is the Ice Sheet System Model(ISSM), an open-source project developed jointlyat JPL and UCI whose main purpose is to model the evolution of the polar ice caps in Greenland and Antarctica. By using ISSM, VISL students have access tostate-of-the-art modeling software that is being used to conduct scientificresearch by users all over the world. However, providing this functionality isby no means simple. The modeling of ice sheets in response to sea and atmospheric temperatures, among many other possible parameters, requiressignificant computational resources. Furthermore, this service needs to beresponsive and capable of handling burst requests produced by classrooms ofstudents. Cloud computing providers represent a burgeoning industry. With majorinvestments by tech giants like Amazon, Google and Microsoft, it has never beeneasier or more affordable to deploy computational elements on-demand. This isexactly what VISL needs and ISSM is capable of. Moreover, this is a promisingalternative to investing in expensive and rapidly devaluing hardware.

Atmospheric Rotational Effects on Mars Based on the NASA Ames General Circulation Model: Angular Momentum Approach

NASA Technical Reports Server (NTRS)

Sanchez, Braulio V.; Haberle, Robert M.; Schaeffer, James

2004-01-01

The objective of the investigation is to determine the motion of the rotational axis of Mars as a result of mass variations in the atmosphere and condensation and sublimation of CO2 ice on the polar caps. A planet experiences this type of motion if it has an atmosphere, which is changing its mass distribution with respect to the solid body of the planet and/or it is asymmetrically changing the amount of ice at the polar caps. The physical principle involved is the conservation of angular momentum, one can get a feeling for it by sitting on a well oiled swivel chair holding a rotating wheel on a horizontal direction and then changing the rotation axis of the wheel to a vertical direction. The person holding the wheel and the chair would begin to rotate in opposite direction to the rotation of the wheel. The motions of Mars atmosphere and the ice caps variations are obtained from a mathematical model developed at the NASA Ames Research Center. The model produces outputs for a time span of one Martian year, which is equivalent to 687 Earth days. The results indicate that Mars axis of rotation moves in a spiral with respect to a reference point on the surface of the planet. It can move as far away as 35.3 cm from the initial location as a result of both mass variations in the atmosphere and asymmetric ice variations at the polar caps. Furthermore the pole performs close to two revolutions around the reference point during a Martian year. This motion is a combination of two motions, one produced by the atmospheric mass variations and another due to the variations in the ice caps. The motion due to the atmospheric variations is a spiral performing about two and a half revolutions around the reference point during which the pole can move as far as 40.9 cm. The motion due to variations in the ice caps is a spiral performing almost three revolutions during which the pole can move as far as 32.8 cm.

Retrieving improved multi-temporal CryoSat elevations over ice caps and glaciers - a case study of Barnes ice cap

NASA Astrophysics Data System (ADS)

Nilsson, Johan; Burgess, David

2014-05-01

The CryoSat mission was launched in 2010 to observe the Earth's cryosphere. In contrast to previous satellite radar altimeters, this mission is expected to monitor the elevation of small ice caps and glaciers, which according to the IPCC will be the largest contributor to 21st century sea level rise. To date the ESA CryoSat SARiN level-2 (L2) elevation product is not yet fully optimized for use over these types of glaciated regions, as its processed with a more universal algorithm. Thus the aim of this study is to demonstrate that with the use of improved processing CryoSat SARiN data can be used for more accurate topography mapping and elevation change detection for ice caps and glaciers. To demonstrate this, elevations and elevation changes over Barnes ice cap, located on Baffin Island in the Canadian Arctic, have been estimated from available data from the years 2010-2013. ESA's CryoSat level-1b (L1b) SARiN baseline "B" data product was used and processed in-house to estimate surface elevations. The resulting product is referred to as DTU-L2. The processing focused on improving the retracker, reducing phase noise and correcting phase ambiguities. The accuracy of the DTU-L2 and the ESA-L2 product was determined by comparing the measured elevations against NASA's IceBridge Airborne Topographic Mapper (ATM) elevations from May 2011. The resulting difference in accuracy was determined by comparing their associated errors. From the multi-temporal measurements spanning the period 2010-2013, elevation changes where estimated and compared to ICESat derived changes from 2003-2009. The result of the study shows good agreement between the NASA measured ATM elevations and the DTU-L2 data. It also shows that the pattern of elevation change is similar to that derived from ICESat data. The accuracy of the DTU-L2 estimated elevations is on average several factors higher compared to the ESA-L2 elevation product. These preliminary results demonstrates that CryoSat elevation data, using improved processing, can be used for accurate topographic mapping and elevation change detection on ice caps and glaciers. Future work would entail extending this processing to other regions of this type to support these results.

The melting sea ice of Arctic polar cap in the summer solstice month and the role of ocean

NASA Astrophysics Data System (ADS)

Lee, S.; Yi, Y.

2014-12-01

The Arctic sea ice is becoming smaller and thinner than climatological standard normal and more fragmented in the early summer. We investigated the widely changing Arctic sea ice using the daily sea ice concentration data. Sea ice data is generated from brightness temperature data derived from the sensors: Defense Meteorological Satellite Program (DMSP)-F13 Special Sensor Microwave/Imagers (SSM/Is), the DMSP-F17 Special Sensor Microwave Imager/Sounder (SSMIS) and the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) instrument on the NASA Earth Observing System (EOS) Aqua satellite. We tried to figure out appearance of arctic sea ice melting region of polar cap from the data of passive microwave sensors. It is hard to explain polar sea ice melting only by atmosphere effects like surface air temperature or wind. Thus, our hypothesis explaining this phenomenon is that the heat from deep undersea in Arctic Ocean ridges and the hydrothermal vents might be contributing to the melting of Arctic sea ice.

Acoustic Monitoring of the Arctic Ice Cap

NASA Astrophysics Data System (ADS)

Porter, D. L.; Goemmer, S. A.; Chayes, D. N.

2012-12-01

Introduction The monitoring of the Arctic Ice Cap is important economically, tactically, and strategically. In the scenario of ice cap retreat, new paths of commerce open, e.g. waterways from Northern Europe to the Far East. Where ship-going commerce is conducted, the U.S. Navy and U.S. Coast Guard have always stood guard and been prepared to assist from acts of nature and of man. It is imperative that in addition to measuring the ice from satellites, e.g. Icesat, that we have an ability to measure the ice extent, its thickness, and roughness. These parameters play an important part in the modeling of the ice and the processes that control its growth or shrinking and its thickness. The proposed system consists of three subsystems. The first subsystem is an acoustic source, the second is an array of geophones and the third is a system to supply energy and transmit the results back to the analysis laboratory. The subsystems are described below. We conclude with a plan on how to tackle this project and the payoff to the ice cap modeler and hence the users, i.e. commerce and defense. System Two historically tested methods to generate a large amplitude multi-frequency sound source include explosives and air guns. A new method developed and tested by the University of Texas, ARL is a combustive Sound Source [Wilson, et al., 1995]. The combustive sound source is a submerged combustion chamber that is filled with the byproducts of the electrolysis of sea water, i.e. Hydrogen and Oxygen, an explosive mixture which is ignited via a spark. Thus, no additional compressors, gases, or explosives need to be transported to the Arctic to generate an acoustic pulse capable of the sediment and the ice. The second subsystem would be geophones capable of listening in the O(10 Hz) range and transmitting that data back to the laboratory. Thus two single arrays of geophones arranged orthogonal to each other with a range of 1000's of kilometers and a combustive sound source where the two arrays intersect would comprise an ice cap monitoring system. The third subsystem is the energy and telemetry required to run the systems. The geophones are low energy compared to the combustive sound source and might be supplied by batteries and a solar panel (at least for half the year). The combustive sound source needs a large continuously energy supply. Two energy harvesting ideas, which need further investigation, are a wind turbine, and a Stirling engine that runs off the temperature difference between the ocean and the atmosphere. Analysis It is expected that the recording of the acoustics energy, as it travels through the ice and is detected by the geophones, will provide estimates of ice anisotropy and coherence. These give estimates of the ice roughness and thickness, respectively, and are key parameters for modeling the changes in the ice cap cover in the Artic. Reference: P. S. Wilson, T. G. Muir, J. A. Behrens, and J. L. Elizey, "Applications of the combustive sound source," J. Acoust. Soc. Am. 97, 3298(A) (1995).

Mass budget of the glaciers and ice caps of the Queen Elizabeth Islands, Canada, from 1991 to 2015

NASA Astrophysics Data System (ADS)

Millan, Romain; Mouginot, Jeremie; Rignot, Eric

2017-02-01

Recent studies indicate that the glaciers and ice caps in Queen Elizabeth Islands (QEI), Canada have experienced an increase in ice mass loss during the last two decades, but the contribution of ice dynamics to this loss is not well known. We present a comprehensive mapping of ice velocity using a suite of satellite data from year 1991 to 2015, combined with ice thickness data from NASA Operation IceBridge, to calculate ice discharge. We find that ice discharge increased significantly after 2011 in Prince of Wales Icefield, maintained or decreased in other sectors, whereas glacier surges have little impact on long-term trends in ice discharge. During 1991-2005, the QEI mass loss averaged 6.3 ± 1.1 Gt yr-1, 52% from ice discharge and the rest from surface mass balance (SMB). During 2005-2014, the mass loss from ice discharge averaged 3.5 ± 0.2 Gt yr-1 (10%) versus 29.6 ± 3.0 Gt yr-1 (90%) from SMB. SMB processes therefore dominate the QEI mass balance, with ice dynamics playing a significant role only in a few basins.

Dual-sensor mapping of mass balance on Russia's northernmost ice caps

NASA Astrophysics Data System (ADS)

Nikolskiy, D.; Malinnikov, V.; Sharov, A.; Ukolova, M.

2012-04-01

Mass balance of Russia's northernmost ice caps is poorly known and scarcely mapped. Thorough information about glacier fluctuations in the outer periphery of Russian shelf seas is both lacking and highly desired since it may constitute the relevant benchmark for judging and projecting climate change impacts in the entire Arctic. The present study is focussed on geodetic measurements and medium-scale mapping of the mass balance on a dozen insular ice caps, some large and some smaller, homogeneously situated along the Eurasian boundary of Central Arctic Basin. The study region extends for approx. 2.200 km from Victoria and Arthur islands in the west across Rudolph, Eva-Liv, Ushakova, Schmidt and Komsomolets islands in the north to Bennett and Henrietta islands in the east thereby comprising the most distant and least studied ice caps in the Russian Arctic. The situation of insular ice masses close to the edge of summer minimum sea ice proved helpful in analysing spatial asymmetry of glacier accumulation signal. The overall mapping of glacier elevation changes and quantification of mass balance characteristics in the study region was performed by comparing reference elevation models of study glaciers derived from Russian topographic maps 1:200,000 (CI = 20 or 40 m) representing the glacier state as in the 1950s-1960s with modern elevation data obtained from satellite radar interferometry and lidar altimetry. In total, 14 ERS and 4 TanDEM-X high-quality SAR interferograms of 1995/96 and 2011 were acquired, processed in the standard 2-pass DINSAR manner, geocoded, calibrated, mosaicked and interpreted using reference elevation models and co-located ICESat altimetry data of 2003-2010. The DINSAR analysis revealed the existence of fast-flowing outlet glaciers at Arthur, Rudolph, Eva-Liv and Bennett islands. The calculation of separate mass-balance components is complicated in this case because of generally unknown glacier velocities and ice discharge values for the mid-20th century. Hence only net balance values were determined for those ice caps. Other ice caps belong to the category of slow-moving or passive glaciers with simpler estimation of mass balance characteristics. Glacier elevation changes on several study glaciers were repeatedly determined with ICESat GLA06 data releases 28 and 29, and statistically compared. The root mean square difference between test determinations was given as less than 1 m rms and the lidar oversaturation effect was neglected in further work. Modern outlines of maritime glacier faces were corrected with the high-resolution optical quicklook imagery obtained from WorldView and QuickBird satellites. The research revealed the reduction of glacier area and general lowering of the glacier surface on most ice caps. Several new islets were discovered due to the glacial retreat in northern parts of Eva-Liv, Schmidt and Komsomolets islands. The cumulative mass budget in the study region remained negative while individual rates of volume change varied from -0.09 km3/a to +0.04 km3/a. Positive values of average mass balance with the maximum accumulation signal of approx. 0.9 m/a were determined on Ushakova, Schmidt and Henrietta ice caps. The results were represented in the form of glacier change maps with 50-m grid at 1:200,000 scale. The vertical accuracy of glacier change maps proved on several small and large ice caps was given as ± 0.3 m/a rms. Several resultant maps can be accessed at http://dib.joanneum.at/MAIRES/index.php?page=products. Further sub-regional comparison of glacier change maps with climatological, oceanographic, rheological, gravimetric and other ground-truth and EO data showed that spatial changes of insular glaciers are closely dependent on the frequency of precipitation events, water depth, sea ice regime, polynyas and gravity anomalies nearby. New opportunities for validating mass changes on the largest study glaciers and determining their bulk density are expected from the next release of GOCE gravity field data and CryoSat-2 radar altimetry data announced by ESA for 2012.

Mars polar cap: a habitat for elementary life1

NASA Astrophysics Data System (ADS)

Wallis, M. K.; Wickramasinghe, N. C.

2009-04-01

Ices in the Martian polar caps are potential habitats for various species of microorganisms. Salts in the ice and biological anti-freeze polymers maintain liquid in cracks in the ices far below 0°C, possibly down to the mean 220-240 K. Sub-surface microbial life is shielded from ultraviolet (UV) radiation, but could potentially be activated on south-facing slopes under the midday, midsummer Sun. Such life would be limited by low levels of vapour, little transport of nutrients, low light levels below a protective dirt-crust, frost accumulation at night and in shadows, and little if any active translocation of organisms. As in the Antarctic and in permafrost, movement to new habitats depends on geo-climatic changes, which for Mars's north polar cap occur on a 50 000 year scale, except for rare meteorite impacts.

Investigation of Martian H2O and CO2 via gamma-ray spectroscopy

NASA Technical Reports Server (NTRS)

Squyres, Steven W.; Evans, Larry G.

1987-01-01

The evolution and present state of water and carbon dioxide on Mars are discussed. Researchers wished to determine how effectively questions regarding the distribution of water and carbon dioxide on Mars may be addressed with orbital gamma ray spectrometer data. Several simple, multi-layer models of the Martian surface were formulated to address problems such as the ice/dust ratio of layered deposits; the distribution, depth and concentration of ground ice; the thickness of north polar perennial ice; the thickness of the carbon dioxide layer over the south polar cap; the thickness of the seasonal carbon dioxide frost cap; and the water content of the seasonal frost cap. The results indicate that the Mars Observer gamma ray spectrometer will be a powerful tool for investigating the distribution and stratigraphy of volatiles on Mars.

Origin of ice-rafted debris: Pleistocene paleoceanography in the western Arctic Ocean

NASA Astrophysics Data System (ADS)

Bischof, Jens; Clark, David L.; Vincent, Jean-Serge

1996-12-01

The composition of Pleistocene ice-rafted debris (IRD) >250 µm was analyzed quantitatively by grain counting in five sediment cores from the western central Arctic Ocean and compared with the composition of till clasts from NW Canada in order to determine the dropstone origin and to reconstruct the Pleistocene ice driftways and surface currents. The IRD composition alternates repeatedly between carbonate- and quartz-dominated assemblages, along with metamorphic and igneous rocks, clastic rocks, and some chert. The highest quartz content is found on the Alpha Ridge, while carbonate percentages are highest on the Northwind Ridge (NWR) and the Chukchi Cap. The source for the carbonates is the area around Banks and Victoria Islands and parts of northern Canada. Quartz most likely originated from the central Queen Elizabeth Islands. IRD on the southeastern Alpha Ridge is dominated by mafic crystalline rocks from northern Ellesmere Island and northern Greenland. At least six major glacial intervals are identified within the last 1 million years, during which icebergs drifted toward the west in the Beaufort Sea, straight northward in the central Arctic Ocean, and northeastward on the SE Alpha Ridge.

Constraints on the Within Season and Between Year Variability of the North Residual Cap from MGS-TES

NASA Technical Reports Server (NTRS)

Calvin, W. M.; Titus, T. N.; Mahoney, S. A.

2003-01-01

There is a long history of telescopic and spacecraft observations of the polar regions of Mars. The finely laminated ice deposits and surrounding layered terrains are commonly thought to contain a record of past climate conditions and change. Understanding the basic nature of the deposits and their mineral and ice constituents is a continued focus of current and future orbited missions. Unresolved issues in Martian polar science include a) the unusual nature of the CO2 ice deposits ("Swiss Cheese", "slab ice" etc.) b) the relationship of the ice deposits to underlying layered units (which differs from the north to the south), c) understanding the seasonal variations and their connections to the finely laminated units observed in high-resolution images and d) the relationship of dark materials in the wind-swept lanes and reentrant valleys to the surrounding dark dune and surface materials. Our work focuses on understanding these issues in relationship to the north residual ice cap. Recent work using Mars Global Surveyor (MGS) data sets have described evolution of the seasonal CO2 frost deposits. In addition, the north polar residual ice cap exhibits albedo variations between Mars years and within the summer season. The Thermal Emission Spectrometer (TES) data set can augment these observations providing additional constraints such as temperature evolution and spectral properties associated with ice and rocky materials. Exploration of these properties is the subject of our current study.

Inception of the Laurentide Ice Sheet using asynchronous coupling of a regional atmospheric model and an ice model

NASA Astrophysics Data System (ADS)

Birch, L.; Cronin, T.; Tziperman, E.

2017-12-01

The climate over the past 0.8 million years has been dominated by ice ages. Ice sheets have grown about every 100 kyrs, starting from warm interglacials, until they spanned continents. State-of-the-art global climate models (GCMs) have difficulty simulating glacial inception, or the transition of Earth's climate from an interglacial to a glacial state. It has been suggested that this failure may be related to their poorly resolved local mountain topography, due to their coarse spatial resolution. We examine this idea as well as the possible role of ice flow dynamics missing in GCMs. We investigate the growth of the Laurentide Ice Sheet at 115 kya by focusing on the mountain glaciers of Canada's Baffin Island, where geologic evidence indicates the last inception occurred. We use the Weather Research and Forecasting model (WRF) in a regional, cloud-resolving configuration with resolved mountain terrain to explore how quickly Baffin Island could become glaciated with the favorable yet realizable conditions of 115 kya insolation, cool summers, and wet winters. Using the model-derived mountain glacier mass balance, we force an ice sheet model based on the shallow-ice approximation, capturing the ice flow that may be critical to the spread of ice sheets away from mountain ice caps. The ice sheet model calculates the surface area newly covered by ice and the change in the ice surface elevation, which we then use to run WRF again. Through this type of iterated asynchronous coupling, we investigate how the regional climate responds to both larger areas of ice cover and changes in ice surface elevation. In addition, we use the NOAH-MP Land model to characterize the importance of land processes, like refreezing. We find that initial ice growth on the Penny Ice Cap causes regional cooling that increases the accumulation on the Barnes Ice Cap. We investigate how ice and topography changes on Baffin Island may impact both the regional climate and the large-scale circulation.

Observations of the north polar region of Mars from the Mars orbiter laser altimeter.

PubMed

Zuber, M T; Smith, D E; Solomon, S C; Abshire, J B; Afzal, R S; Aharonson, O; Fishbaugh, K; Ford, P G; Frey, H V; Garvin, J B; Head, J W; Ivanov, A B; Johnson, C L; Muhleman, D O; Neumann, G A; Pettengill, G H; Phillips, R J; Sun, X; Zwally, H J; Banerdt, W B; Duxbury, T C

1998-12-11

Elevations from the Mars Orbiter Laser Altimeter (MOLA) have been used to construct a precise topographic map of the martian north polar region. The northern ice cap has a maximum elevation of 3 kilometers above its surroundings but lies within a 5-kilometer-deep hemispheric depression that is contiguous with the area into which most outflow channels emptied. Polar cap topography displays evidence of modification by ablation, flow, and wind and is consistent with a primarily H2O composition. Correlation of topography with images suggests that the cap was more spatially extensive in the past. The cap volume of 1.2 x 10(6) to 1.7 x 10(6) cubic kilometers is about half that of the Greenland ice cap. Clouds observed over the polar cap are likely composed of CO2 that condensed out of the atmosphere during northern hemisphere winter. Many clouds exhibit dynamical structure likely caused by the interaction of propagating wave fronts with surface topography.

Annual glacier dammed lake drainage in Zackenberg, Northeast Greenland

NASA Astrophysics Data System (ADS)

Lane, Timothy; Adamson, Kathryn; Matthews, Tom

2016-04-01

A.P. Olsen is a 295 km2 ice cap in the Zackenberg region of Northeast Greenland (74.6° N, 21.5° W), 35 km from the ZERO Zackenberg Research Station. The ice cap lies on a gneissic plateau, covering an elevation of 200 to 1450 m a.s.l. A.P. Olsen mass balance has been monitored since 2008 and reconstructed for the period 1995-2007. Meltwater from this ice cap drains into the Zackenberg River, and into Young Sund via the Zackenberg Delta. One outlet dams a c. 0.8 km2 lake fed by the northern part of the ice cap. Observational data suggests this lake drains annually, flooding subglacially into the Zackenberg River. But the impacts of these flood events on the hydrology, sediment transfer, and geomorphology of the proglacial zone downstream have not been examined in detail. Understanding the impacts of glacial lake outburst flood events is important in the sensitive Arctic environment, where glacial change is rapid. We use Landsat scenes to reconstruct lake extent from 1999-2015. This is compared to Zackenberg River discharge measurements, available from the ZERO Zackenberg monitoring programme. These datasets are used to examine the nature and timing of flood events, and assess the impacts on the Zackenberg river downstream.

InSAR Observations and Finite Element Modeling of Crustal Deformation Around a Surging Glacier, Iceland

NASA Astrophysics Data System (ADS)

Spaans, K.; Auriac, A.; Sigmundsson, F.; Hooper, A. J.; Bjornsson, H.; Pálsson, F.; Pinel, V.; Feigl, K. L.

2014-12-01

Icelandic ice caps, covering ~11% of the country, are known to be surging glaciers. Such process implies an important local crustal subsidence due to the large ice mass being transported to the ice edge during the surge in a few months only. In 1993-1995, a glacial surge occurred at four neighboring outlet glaciers in the southwestern part of Vatnajökull ice cap, the largest ice cap in Iceland. We estimated that ~16±1 km3 of ice have been moved during this event while the fronts of some of the outlet glaciers advanced by ~1 km.Surface deformation associated with this surge has been surveyed using Interferometric Synthetic Aperture Radar (InSAR) acquisitions from 1992-2002, providing high resolution ground observations of the study area. The data show about 75 mm subsidence at the ice edge of the outlet glaciers following the transport of the large volume of ice during the surge (Fig. 1). The long time span covered by the InSAR images enabled us to remove ~12 mm/yr of uplift occurring in this area due to glacial isostatic adjustment from the retreat of Vatnajökull ice cap since the end of the Little Ice Age in Iceland. We then used finite element modeling to investigate the elastic Earth response to the surge, as well as confirm that no significant viscoelastic deformation occurred as a consequence of the surge. A statistical approach based on Bayes' rule was used to compare the models to the observations and obtain an estimate of the Young's modulus (E) and Poisson's ratio (v) in Iceland. The best-fitting models are those using a one-kilometer thick top layer with v=0.17 and E between 12.9-15.3 GPa underlain by a layer with v=0.25 and E from 67.3 to 81.9 GPa. Results demonstrate that InSAR data and finite element models can be used successfully to reproduce crustal deformation induced by ice mass variations at Icelandic ice caps.Fig. 1: Interferograms spanning 1993 July 31 to 1995 June 19, showing the surge at Tungnaárjökull (Tu.), Skaftárjökull (Sk.) and Síðujökull (Sí.) outlet glaciers. The black and grey arrows show the azimuth of the satellite and the look direction, respectively. (a) Wrapped interferogram showing the surge deformation (2π = 28.3 mm deformation). (b) Unwrapped interferogram with the black star as the reference area and negative values indicating line of sight lengthening (Auriac et al., 2014, doi:10.1093/gji/ggu205).

Recent Changes in Arctic Glaciers, Ice Caps, and the Greenland Ice Sheet: Cold Facts About Warm Ice

NASA Astrophysics Data System (ADS)

Abdalati, W.

2005-12-01

One of the major manifestations of Arctic change can be observed in the state of balance of Arctic glaciers and ice caps and the Greenland ice sheet. These ice masses are estimated to contain nearly 3 million cubic kilometers of ice, which is more than six times greater than all the water stored in the Earth's lakes, rivers, and snow combined and is the equivalent of over 7 meters of sea level. Most of these ice masses have been shrinking in recent in years, but their mass balance is highly variable on a wide range of spatial and temporal scales. On the Greenland ice sheet most of the coastal regions have thinned substantially as melt has increased and some of its outlet glaciers have accelerated. Near the equilibrium line in West Greenland, we have seen evidence of summer acceleration that is linked to surface meltwater production, suggesting a relatively rapid response mechanism of the ice sheet change to a warming climate. At the same time, however, the vast interior regions of the Greenland ice sheet have shown little change or slight growth, as accumulation in these areas may have increased. Throughout much of the rest of the Arctic, many glaciers and ice caps have been shrinking in the past few decades, and in Canada and Alaska, the rate of ice loss seems to have accelerated during the late 1990s. These recent observations offer only a snapshot in time of the long-term behavior, but they are providing crucial information about the current state of ice mass balance and the mechanisms that control it in one of the most climatically sensitive regions on Earth. As we continue to learn more through a combination of remote sensing observations, in situ measurements and improved modeling capabilities, it is important that we coordinate and integrate these approaches effectively in order to predict future changes and their impact on sea level, freshwater discharge, and ocean circulation.

Is the 20th century warming unprecedented in the Siberian north?

NASA Astrophysics Data System (ADS)

Sidorova, Olga V.; Saurer, Matthias; Andreev, Andrei; Fritzsche, Diedrich; Opel, Thomas; Naurzbaev, Mukhtar M.; Siegwolf, Rolf

2013-08-01

To answer the question "Has the recent warming no analogues in the Siberian north?" we analyzed larch tree samples (Larix gmelinii Rupr.) from permafrost zone in the eastern Taimyr (TAY) (72°N, 102°E) using tree-ring and stable isotope analyses for the Climatic Optimum Period (COP) 4111-3806 BC and Medieval Warm Period (MWP) 917-1150 AD, in comparison to the recent period (RP) 1791-2008 AD. We developed a description of the climatic and environmental changes in the eastern Taimyr using tree-ring width and stable isotope (δ13C, δ18O) data based on statistical verification of the relationships to climatic parameters (temperature and precipitation). Additionally, we compared our new tree-ring and stable isotope data sets with earlier published July temperature and precipitation reconstructions inferred from pollen data of the Lama Lake, Taimyr Peninsula, δ18O ice core data from Akademii Nauk ice cap on Severnaya Zemlya (SZ) and δ18O ice core data from Greenland (GISP2), as well as tree-ring width and stable carbon and oxygen isotope data from northeastern Yakutia (YAK). We found that the COP in TAY was warmer and drier compared to the MWP but rather similar to the RP. Our results indicate that the MWP in TAY started earlier and was wetter than in YAK. July precipitation reconstructions obtained from pollen data of the Lama Lake, oxygen isotope data from SZ and our carbon isotopes in tree cellulose agree well and indicate wetter climate conditions during the MWP. Consistent large-scale patterns were reflected in significant links between oxygen isotope data in tree cellulose from TAY and YAK, and oxygen isotope data from SZ and GISP2 during the MWP and the RP. Finally, we showed that the recent warming is not unprecedented in the Siberian north. Similar climate conditions were recorded by tree-rings, stable isotopes, pollen, and ice core data 6000 years ago.

Method and design for externally applied laser welding of internal connections in a high power electrochemical cell

DOEpatents

Martin, Charles E; Fontaine, Lucien; Gardner, William H

2014-01-21

An electrochemical cell includes components that are welded from an external source after the components are assembled in a cell canister. The cell canister houses electrode tabs and a core insert. An end cap insert is disposed opposite the core insert. An external weld source, such as a laser beam, is applied to the end cap insert, such that the end cap insert, the electrode tabs, and the core insert are electrically coupled by a weld which extends from the end cap insert to the core insert.

High-Resolution ∂18O record of middle-late Holocene hydrologic variability from the central Peruvian Andes (Invited)

NASA Astrophysics Data System (ADS)

Rodbell, D. T.; Abbott, M.; Bird, B. W.; Stansell, N.

2009-12-01

Laguna Yuraicocha in the western cordillera of the central Peruvian Andes (12.53°S; 75.50°W; 4460 masl) is dammed by late glacial moraines and is underlain and surrounded by Jurassic and Cretaceous limestone interbedded with siliciclastic rocks. A 6.9 meter-long sediment core from the distal end of the lake is dominated by authigenic calcite (marl) with a mean concentration of 82 weight percent that has accumulated at a rate of ~ 1 mm yr-1 for the past 6200 years. The age model for the core is based on a combination of 210Pb and AMS 14C ages from charcoal; modern lake water is ~1‰ evaporatively enriched from mean regional precipitation. Marl samples were taken with an average sampling interval of 8 years; samples were treated to remove organic matter, sieved to concentrate the <75 µm fraction, and the clay fraction was removed by repeated pipette withdrawal. The <75 µm fraction contains abundant euhedral grains of calcite that are not abraded or corroded, thus reflecting their authigenic origin in Laguna Yuraicocha. The 18O and 13C stratigraphy reveals decadal, century, and millennial-scale variability that is comparable to isotope records from other carbonate lakes and ice cores in the region. The 18O and 13C records generally covary with similar amplitudes; δ13C ranges from -0.5 to 3.5 ‰ (PDB). A pronounced linear trend of δ18O depletion (from -10.5 to -14.5 ‰) spans the length of record and likely reflects a progressive increase in hydrologic balance (i.e., the ratio of precipitation/evaporation) through the middle and late Holocene. This interpretation is consistent with basal core sediment that records pronounced lake low stands, and possible periodic dessication in the early-middle Holocene. The last 1200 yr of record reveals a 2‰ depletion culminating with the most depleted isotopes on record ~ AD 1800 followed by an abrupt 1.5 ‰ enrichment that began ~AD 1900 and continues to the present. These trends match closely the 18O record from the Quelccaya Ice Cap implying a regional moisture balance control on isotopic records from lakes and ice cores in the tropical Andes. Subcentennial variance in 18O with an ~2‰ amplitude is persistent throughout the record. Time series analysis reveals strength in the 5-12 year window, which may record the influence of ENSO on the hydrologic balance of the region through its effect on the strength of the South American summer monsoon. Spectral strength is also present in the 40-200 year periodicity and this spectral component appears to weaken in the last millennium. The progressive increase in hydrologic balance during the middle-late Holocene is consistent with glacial geologic evidence for the onset of neoglaciation in the Peruvian Andes, including the dramatic reformation of the Quelccaya Ice Cap ~5100 years ago. This appears to confirm the notion that Andean glaciers, especially those in the southern and western cordillera of Peru and Bolivia, are especially sensitive to changes in regional moisture balance.

Hemodynamic and Thermal Responses to Head and Neck Cooling in Men and Women

NASA Technical Reports Server (NTRS)

Ku, Yu-Tsuan E.; Montgomery, Leslie D.; Carbo, Jorge E.; Webbon, Bruce W.

1995-01-01

Personal cooling systems are used to alleviate symptoms of multiple sclerosis and to prevent increased core temperature during daily activities. Configurations of these systems include passive ice vests and circulating liquid cooling garments (LCGs) in the forms of vests, cooling caps and combined head and neck cooling systems. However, little information is available oil the amount or heat that can be extracted from the body with these systems or the physiologic changes produced by routine operation of these systems. The objective of this study was to determine the operating characteristics and the physiologic change, produced by short term use of one commercially available thermal control system.

Spatial variability in the seasonal south polar CAP of Mars

NASA Astrophysics Data System (ADS)

Calvin, Wendy M.; Martin, Terry Z.

1994-10-01

The first comprehensive discussion of the south seasonal polar cap spectra obtained by the Mariner 7 infrared spectrometer in the short-wavelength region (2-4 microns) is presented. The infrared spectra is correlated with images acquired by the wide-angle camera. Significant spectral variation is noted in the cap interior and regions of varying water frost abundance, CO2 ice/frost cover, and CO2-ice path length can be distinguished. Many of these spectral variations correlate with heterogeneity noted in the camera images, but certain significant infrared spectral variations are not discernible in the visible. Simple reflectance models are used to classify the observed spectral variations into four regions. Region I is at the cap edge, where there is enhanced absorption beyond 3 microns inferred to be caused by an increased abundance of water frost. The increase in water abundance over that in the interior is on the level of a few parts per thousand or less. Region II is the typical cap interior characterized by spectral features of CO2 ice at grain sizes of several millimeters to centimeters. These spectra also indicate the presence of water frost at the parts per thousand level. A third, unusual region (III), is defined by three spectra in which weak CO2 absorption features are as much as twice as strong as in the average cap spectra and are assumed to be caused by an increased path length in the CO2. Such large paths are inconsistent with the high reflectance in the visible and at 2.2 microns and suggest layered structures or deposition conditions that are not accounted for in current reflectance models. The final region (IV) is an area of thinning frost coverage or transparent ice well in the interior of the seasonal cap. These spectra are a combination of CO2 and ground signatures.

Spatial variability in the seasonal south polar cap of Mars

NASA Technical Reports Server (NTRS)

Calvin, Wendy M.; Martin, Terry Z.

1994-01-01

The first comprehensive discussion of the south seasonal polar cap spectra obtained by the Mariner 7 infrared spectrometer in the short-wavelength region (2-4 microns) is presented. The infrared spectra is correlated with images acquired by the wide-angle camera. Significant spectral variation is noted in the cap interior and regions of varying water frost abundance, CO2 ice/frost cover, and CO2-ice path length can be distinguished. Many of these spectral variations correlate with heterogeneity noted in the camera images, but certain significant infrared spectral variations are not discernible in the visible. Simple reflectance models are used to classify the observed spectral variations into four regions. Region I is at the cap edge, where there is enhanced absorption beyond 3 microns inferred to be caused by an increased abundance of water frost. The increase in water abundance over that in the interior is on the level of a few parts per thousand or less. Region II is the typical cap interior characterized by spectral features of CO2 ice at grain sizes of several millimeters to centimeters. These spectra also indicate the presence of water frost at the parts per thousand level. A third, unusual region (III), is defined by three spectra in which weak CO2 absorption features are as much as twice as strong as in the average cap spectra and are assumed to be caused by an increased path length in the CO2. Such large paths are inconsistent with the high reflectance in the visible and at 2.2 microns and suggest layered structures or deposition conditions that are not accounted for in current reflectance models. The final region (IV) is an area of thinning frost coverage or transparent ice well in the interior of the seasonal cap. These spectra are a combination of CO2 and ground signatures.

Testing Orbital Parameters as a Hypothesis for the Presence of CO2 Deposits on Mars's South Pole

NASA Astrophysics Data System (ADS)

Bain, Z. M.; Bierson, C. J.

2017-12-01

Observational data of Mars's polar caps shows large deposits of buried CO2 ice in the south polar cap and only seasonal CO2 ice in the north [1]. The lower elevation of Mars's north pole leads to higher surface pressures and therefore more favorable conditions for CO2 ice deposition. There are a few plausible reasons why the CO2 deposits are observed at the southern cap. The first is that during a past epochs of atmospheric collapse, CO2was deposited at both poles and only preserved in the south. Another is that the deposits represent a period where ice was preferentially deposited at the south polar cap. The latter could occur if the orbital parameters were such that the southern cap experienced colder summers (less insolation) than the north. The model of Bierson et. al. 2016 [2] used the observed difference in albedo between the north and the south polar caps and found several periods in the last one million years where deposition was favored at the south polar cap. Here we test if deposition is still favored in the south using the same albedo for both caps. For this work we are using the seasonally resolved KRC model [3]. We varied obliquity, longitude of perihelion, and eccentricity to match their expected values over the last one million years [4]. We modeled the annual CO2 deposition rate in 1,000 year increments. We tested both constant and insolation dependent albedo that was the same at both poles. While we did find periods of deposition on the south pole, this was always in conjunction with deposition in the north in much greater amounts. This finding favors the hypothesis that the deposits are only observed in the southern cap due to the deep pre-existing troughs that allowed the CO2 to be preserved to the modern day. These results also highlight the importance of understanding the observed difference in albedo between the polar caps. [1] Phillips et al. (2011) AAAS, Vol.332 Is.6031 pp.838-841 [2] Bierson et al. (2016) GRL, Vol.43 Is.9 pp.4172-4179 [3] Kieffer (2013) JGR, Vol.118 Is.3 pp.451-470 [4] Laskar et al. (2004) Icarus, Vol.170 Is.2 pp.343-364

Influence of Gígjökull on the Emplacement of the Lava Flow Produced by the 2010 Eruption of Eyjafjallajökull, Iceland, and the Flow's Effects on the Glacier's Resilience to Climate Change

NASA Astrophysics Data System (ADS)

Dougherty, W.; Edwards, B. R.; Kochtitzky, W. H.; Oddsson, B.; Gudmundsson, M. T.

2017-12-01

While more than 180 volcanoes on Earth are presently glaciated (Edwards and Kochtitzky, 2014), few studies have examined the long-term impact of a specific eruption on the affected glacier. The 2010 eruption of Eyjafjallajökull in south-central Iceland significantly damaged the small summit ice cap as well as Gígjökull, a valley glacier on the north side of the volcano. Up until the eruption in April 2010, the terminus of Gígjökull was a glacial lagoon confined by a terminal moraine. During the eruption, melting of the ice cap and valley glacier produced floods that flushed out the lagoon and infilled it with sediment. Currently, several very small lakes exist in the former lagoon, which is drained by a small stream. We documented the damage to the ice cap and Gígjökull in July 2010 on aerial overflights and the glaciers' reaction to the eruption. We again made aerial observations of the glaciers in 2011 and 2012, and have continued to monitor their changes from ground-based images. Immediately after the eruption a hole was present in the summit ice cap, containing a small lake. A complete passage from the summit ice cap to within 1 km of the glacier terminus had been melted, and was filled with volcanic debris. The damaged parts of Gígjökull included a wide opening near the head of the glacier, from which a lava flow traveled during the eruption. A canyon was melted in the ice below the vent. By summer 2011 an ice tongue was migrating into the crater from the south side of the crater rim. As of June 2017, Gígjökull had advanced to cover most of the 2010 lava flow, suggesting some glacial recovery, but no more than an isolated ice tongue, no longer fed by the main glacier, reached the lower part of the valley where the lagoon previously existed, and the glacier terminated before the 2010 eruption. Studies of Gígjökull provide insight on glaciers' influences on lava flow emplacement as well as the ability of a glacier to recover after major volcanic disturbances.

Carbon Dioxide Landforms

NASA Technical Reports Server (NTRS)

2004-01-01

19 March 2004 The martian south polar residual ice cap is mostly made of frozen carbon dioxide. There is no place on Earth that a person can go to see the landforms that would be produced by erosion and sublimation of hundreds or thousands of cubic kilometers of carbon dioxide. Thus, the south polar cap of Mars is as alien as alien can get. This image, acquired in February 2004 by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC), shows how the cap appears in summer as carbon dioxide is subliming away, creating a wild pattern of pits, mesas, and buttes. Darker surfaces may be areas where the ice contains impurities, such as dust, or where the surface has been roughened by the removal of ice. This image is located near 86.3oS, 0.8oW. This picture covers an area about 3 km (1.9 mi) across. Sunlight illuminates the scene from the top/upper left.

Research Spotlight: No tipping point for Arctic Ocean ice

NASA Astrophysics Data System (ADS)

Schultz, Colin

2011-03-01

Declines in the summer sea ice extent have led to concerns within the scientific community that the Arctic Ocean may be nearing a tipping point, beyond which the sea ice cap could not recover. In such a scenario, greenhouse gases in the atmosphere trap outgoing radiation, and as the Sun beats down 24 hours a day during the Arctic summer, temperatures rise and melt what remains of the polar sea ice cap. The Arctic Ocean, now less reflective, would absorb more of the Sun’s warmth, a feedback loop that would keep the ocean ice free. However, new research by Tietsche et al. suggests that even if the Arctic Ocean sees an ice-free summer, it would not lead to catastrophic runaway ice melt. The researchers, using a general circulation model of the global ocean and the atmosphere, found that Arctic sea ice recovers within 2 years of an imposed ice-free summer to the conditions dictated by general climate conditions during that time. Furthermore, they found that this quick recovery occurs whether the ice-free summer is triggered in 2000 or in 2060, when global temperatures are predicted to be 2°C warmer. (Geophysical Research Letters, doi:10.1029/2010GL045698, 2011)

Spatial Variability of Climate Signatures Recorded in an Array of Shallow Firn Cores from the Western Greenland Percolation Zone

NASA Astrophysics Data System (ADS)

Thundercloud, Z. R.; Osterberg, E. C.; Ferris, D. G.; Graeter, K.; Lewis, G.; Hawley, R. L.; Marshall, H. P.

2016-12-01

Greenland ice cores provide seasonally to annually resolved proxy records of past temperature, accumulation and atmospheric circulation. Most Greenland ice cores have been collected from the dry snow zone at elevations greater than 2500 m to produce records of North Atlantic paleoclimate over the last full glacial cycle. Ice cores collected from more costal regions, however, provide the opportunity to develop regional-scale records of climate conditions along ice sheet margins where recent temperature and precipitation changes have been larger than those in the ice sheet interior. These cores are more readily comparable to lake sediment and landscape (i.e. moraine) records from the ice sheet margin, and are potentially more sensitive to sea-ice variability due to the proximity to the coast. Here we present major ion and stable isotope records from an array of firn cores (40-55 year records) collected in the western Greenland percolation zone, and assess the spatial variability of ice core statistical relationships with the North Atlantic Oscillation (NAO) and Baffin Bay sea ice extent. Seven cores were collected from elevations of 2100-2500 m along a 400-km segment of the ice sheet from Dye-2 to Milcent as part of the Greenland Traverse for Accumulation and Climate Studies (GreenTrACS) project from May-June 2016. They were sampled by a continuous melter system at Dartmouth College, and analyzed using Dionex ion chromatographs and a Picarro L2130-i laser ring-down spectrometer. We focus on the signature of the NAO and Baffin Bay sea ice extent in the sea-salt, dust, deuterium excess (d-excess), and methanesulfonic acid (MSA) firn core records, and assess the special variability of these climate-ice core relationships across the study area. Climate reanalysis data indicate that NAO-ice core correlations should be stronger at lower elevation in the percolation zone than high in the dry snow zone. Our results will provide valuable insight into the sensitivity of Greenland ice core paleoclimate reconstructions to the specific ice core location, and thereby aid in site selection for deeper ice cores that could span the Holocene.

Probability modeling of the number of positive cores in a prostate cancer biopsy session, with applications.

PubMed

Serfling, Robert; Ogola, Gerald

2016-02-10

Among men, prostate cancer (CaP) is the most common newly diagnosed cancer and the second leading cause of death from cancer. A major issue of very large scale is avoiding both over-treatment and under-treatment of CaP cases. The central challenge is deciding clinical significance or insignificance when the CaP biopsy results are positive but only marginally so. A related concern is deciding how to increase the number of biopsy cores for larger prostates. As a foundation for improved choice of number of cores and improved interpretation of biopsy results, we develop a probability model for the number of positive cores found in a biopsy, given the total number of cores, the volumes of the tumor nodules, and - very importantly - the prostate volume. Also, three applications are carried out: guidelines for the number of cores as a function of prostate volume, decision rules for insignificant versus significant CaP using number of positive cores, and, using prior distributions on total tumor size, Bayesian posterior probabilities for insignificant CaP and posterior median CaP. The model-based results have generality of application, take prostate volume into account, and provide attractive tradeoffs of specificity versus sensitivity. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Post-Industrial Revolution changes in large-scale atmospheric pollution of the northern hemisphere by heavy metals as documented in central Greenland snow and ice

NASA Astrophysics Data System (ADS)

Candelone, Jean-Pierre; Hong, Sungmin; Pellone, Christian; Boutron, Claude F.

1995-08-01

Pb, Zn, Cd and Cu have been measured using ultraclean procedures in various sections of a 70.3-m snow/ice core covering the past 220 years (including the Industrial Revolution) drilled at Summit, central Greenland. These time series are the first reliable ones ever published for Zn, Cd, and Cu; for Pb they are the first verification of the pioneering data published more than two decades ago by C. Patterson and his coworkers [Murozumi et al., 1969]. For all four heavy metals, concentrations are found to have markedly increased up until the 1960s and 1970s before decreasing significantly during the following few decades. The timing and the amplitude of the observed changes differ significantly however from one metal to another. Comparison with concentration values obtained by analyzing ancient Holocene ice dated 7760 years B.P., that is, before humans started to impact on the atmosphere, show that no detectable increase occurred for Zn, Cd, and Cu before the Industrial Revolution. On the other hand, Pb concentrations were already one order of magnitude above natural values in late 18th century ice. Cumulative deposition of heavy metals to the whole Greenland ice cap since the Industrial Revolution ranges from 3200 t for Pb to 60 t for Cd.

Modern climate challenges and the geological record

USGS Publications Warehouse

Cronin, Thomas M.

2010-01-01

Today's changing climate poses challenges about the influence of human activity, such as greenhouse gas emissions and land use changes, the natural variability of Earth's climate, and complex feedback processes. Ice core and instrumental records show that over the last century, atmospheric carbon dioxide (CO2) concentrations have risen to 390 parts per million volume (ppmv), about 40% above pre-Industrial Age concentrations of 280 ppmv and nearly twice those of the last glacial maximum about 22,000 years ago. Similar historical increases are recorded in atmospheric methane (CH4) and nitrous oxide (N2O). There is general agreement that human activity is largely responsible for these trends. Substantial evidence also suggests that elevated greenhouse gas concentrations are responsible for much of the recent atmospheric and oceanic warming, rising sea level, declining Arctic sea-ice cover, retreating glaciers and small ice caps, decreased mass balance of the Greenland and parts of the Antarctic ice sheets, and decreasing ocean pH (ocean "acidification"). Elevated CO2 concentrations raise concern not only from observations of the climate system, but because feedbacks associated with reduced reflectivity from in land and sea ice, sea level, and land vegetation relatively slowly (centuries or longer) to elevated 2 levels. This means that additional human-induced climate change is expected even if the rate of CO2 emissions is reduced or concentrations immediately stabilized.

Soil geomorphology and morphometric analysis to approach denudation rates and geomorphological evolution of Limnopolar basin; Byers Plateau

NASA Astrophysics Data System (ADS)

Fernandez, Susana del Carmen; De Pablo, Miguel Angel; Otero, Xose Luis; Quesada, Antonio

2015-04-01

Limnopolar Lake is located in Byers Peninsula Plateau at 85-100m a.s.l. in maritime Antarctic environment. The peninsula, in the western end of Livingston Island, (latitude 62°34'35" S, longitude 61°13'07" W) has more favourable environmental conditions for soil development than other Antarctic regions. Finished the glacial climate conditions in the area began the weathering and edaphic processes. There are several attempts to date the Domo's Roctch cap melting in Byers peninsula based on limnological records studies giving dates of 9.5, 8.3, 6.0 and 5.0 Ka BP while was dated in 6.3 Ka BP in the basis of neotectonic approach. Nevertheless some authors have documented a period of glacial re-advance in the South Shetland Islands from around 7.0 Ka BP, persisting even until 5.0 Ka BP. During cup ice melting mainly isostatic but also tectonic (4%) uplift of the area free of ice started. Based on the date of marine terrace system (70, 55 and 24 m a.s.l.) developed in free of ice coast of the Livingstone Inland a rate of uplift of 0.4 m/Ka was stablished. General speaking that the melting of the ice cap resulted in the establishment of a lacustrine system spread all over Byers peninsula. At a first stage of evolution waters from the ice melting flooded preexisting topographic depressions lead lakes, while an incipient river networks were developing. Nevertheless, hypsometric integral of Limnopolar watershed shows the existence of at least three downcutting steps into Byers Plateau and the lake is located over the last step above the nick point of the river which is incised into glacial deposit. The base of the sedimentary record of the lake was found at 234 cm of deep and dated at about 8.3 Ka BP but corresponds to glacial sediments. In the same core sample, the change to lacustrine characteristics was found at about 211 cm and dated in 6.7 Ka BP. On the other hand, shore of the lake is excavated at 20 m from the upper part of the basin and the transversal profile of valley shows U- shape seem to indicate that the Limnopolar lake basin should evolve as a glacial alpine valley during a period between Domo's Roctch cap melting and the total establishment of the periglacial conditions. The morphometric analysis of Limnopolar basin using DEM, including hypsometric integral analysis and reconstruction of old non-eroded topography via Gis techniques to estimate valley incision rates in relation to the uplift of the area seems to indicate that post melting of ice cap 9.5 Ka BP ago a less intense glacial re-advance took place in which alpine glacial valleys were developed. Moreover, the geochemical state of Fe , Mn and Organic Carbon of 15 soils sampled in the base on very detailed geomorphological map (1:500) show scarce development of edaphic processes and lack of tephra particles highlighting that the soils began to evolve very recently.

Brief communication: Getting Greenland's glaciers right - a new data set of all official Greenlandic glacier names

NASA Astrophysics Data System (ADS)

Bjørk, A. A.; Kruse, L. M.; Michaelsen, P. B.

2015-12-01

Place names in Greenland can be difficult to get right, as they are a mix of Greenlandic, Danish, and other foreign languages. In addition, orthographies have changed over time. With this new data set, we give the researcher working with Greenlandic glaciers the proper tool to find the correct name for glaciers and ice caps in Greenland and to locate glaciers described in the historic literature with the old Greenlandic orthography. The data set contains information on the names of 733 glaciers, 285 originating from the Greenland Ice Sheet (GrIS) and 448 from local glaciers and ice caps (LGICs).

The North Water Polynya and Velocity, Calving Front and Mass Change in Surrounding Glaciers in Greenland and Canada Over the Last 30 Years

NASA Astrophysics Data System (ADS)

Edwards, L.

2015-12-01

Major uncertainties surround future estimates of sea level rise attributable to mass loss from Greenland and the surrounding ice caps in Canada. Understanding changes across these regions is vital as their glaciers have experienced dramatic changes in recent times. Attention has focused on the periphery of these regions where land ice meets the ocean and where ice acceleration, thinning and increased calving have been observed. Polynyas are areas of open water within sea ice which remain unfrozen for much of the year. They vary significantly in size (~3 km2 to > ~85,000 km2 in the Arctic), recurrence rates and duration. Despite their relatively small size, polynyas strongly impact regional oceanography and play a vital role in heat and moisture exchange between the polar oceans and atmosphere. Where polynyas are present adjacent to tidewater glaciers their influence on ocean circulation and water temperatures has the potential to play a major part in controlling subsurface ice melt rates by impacting on the water masses reaching the calving front. They also have the potential to influence air masses reaching nearby glaciers and ice caps by creating a maritime climate which may impact on the glaciers' accumulation and surface melt and hence their thickness and mass balance. Polynya presence and size also have implications for sea ice extent and therefore may influence the buttressing effect on neighbouring tidewater glaciers. The work presented uses remote sensing and mass balance model data to study changes in the North Water polynya (extent, ice concentration, duration) and neighbouring glaciers and ice caps (velocities, calving front positions and mass balance) in Canada and Greenland over a period of approximately 30 years from the mid-1980s through to 2015.

Peruvian Tropical Glacier May Survive Longer Than Previously Thought: Landsat Image Analysis of Nevado Coropuna Ice Cap, Peru

NASA Astrophysics Data System (ADS)

Kochtitzky, W. H.; Edwards, B. R.; Marino, J.; Manrique, N.

2015-12-01

Nevado Coropuna is a large volcanic complex in southern Peru (15.56°S, 72.62°N; 6,425 m). The complex is approximately 12 km east-west and 8 km north-south with elevation from ~4,500 m at the base to over 6,000 m at the highest points. This ice cap is the largest hosted by a volcano in the tropics, and one of the ten biggest ice masses in the tropics. Previous workers have predicted that the Coropuna ice cap will completely melt by 2050. We present a new analysis of historic satellite imagery to test this hypothesis. In this study, ice and snow are classified based on unique spectral signatures including spectral band thresholds, Normalized Difference Snow Index, and Band 4/5 ratio. Landsat scenes (L2, 4, 5, 7, and 8) from 1975 to present in addition to one SPOT scene (2013) are used. Previous workers used images from June and July, which are peak snow periods in southern Peru, leading to overestimates of ice area. This study uses November and December images when snow is at an annual minimum. Annual equilibrium line altitudes are calculated for each end of year image (November/December). The glaciers of Nevado Coropuna were found to be shrinking at ~0.5 km2/yr, which is ~1/3 the rate previously published. In this study, SPOT (1.5 m resolution) and Landsat 7 ETM scenes from November 23 and 26, 2013 respectively were used to calibrate the spectral band threshold classification. While this study suggests that the ice cap of Coropuna will persist until 2100 given current rates, water quantity and security remains a concern for Peruvian agriculture. Coropuna is an active volcano, so it poses great risk to surrounding inhabitants from lahars, flooding, and debris avalanches. Our new data suggest that these will continue to be risks late into this century.

Subglacial carbonate precipitates on central Baffin Island, Arctic Canada may constrain basal conditions for the Foxe sector of the Laurentide Ice Sheet

NASA Astrophysics Data System (ADS)

Miller, G. H.; Refsnider, K. A.

2009-12-01

Extensive, widespread carbonate deposits on gneissic bedrock have recently been discovered around the Barnes Ice Cap, central Baffin Island. Deposits range from conglomeratic crack-fillings ≤5 cm thick to laminated, striated films plastered on bedrock surfaces, often in the lee of obstacles. A single outcrop of these carbonates was first described by Andrews et al. (1972, Canadian Journal of Earth Sciences, 9, 233-238) and was interpreted as an early Tertiary limestone based on the presence of warm-climate palynomorphs including Liriodendron (tulip tree), Ulmus (elm), and Taxodium (cypress). However, recent fieldwork in the region has demonstrated that these carbonates are far more ubiquitous than previously thought and found on both glacially-polished bedrock surfaces and till boulders that melted out in recent decades from Laurentide ice at the base of the Barnes Ice Cap. In many cases, these carbonates exhibit the characteristic morphologies of subglacial carbonates (flutes, furrows, and striations parallel to the direction of ice flow, columnar spicules, and tufa-dam-like forms). A few deposits include angular sands, gravels, and pebbles. The nearest carbonate bedrock is Paleozoic limestone flooring Foxe Basin 130 km west of the Barnes Ice Cap summit. While subglacial carbonate deposits have been documented adjacent to retreating mountain and outlet glaciers and in areas previously covered by Pleistocene ice sheets, few localities are distant from carbonate bedrock. Thus, the carbon required for carbonate deposition in the Barnes region was either (1) derived from Paleozoic limestone and dissolved in subglacial water that was subject to long-distance transport, or (2) there was sufficient trapped atmospheric CO2 in the ice to yield alkaline basal meltwater which hydrolyzed calcium-bearing silicates in the local bedrock. Given the volume of carbonate deposited at some sites, we find the latter model unlikely. If the former model is applicable, these carbonates will provide considerable insight into subglacial processes beneath the Foxe sector of the Laurentide Ice Sheet and possibly constrain the former ice thicknesses above these sites. Quantitative x-ray diffraction defines the mineralogy of both the carbonate and clastic components. Carbon and strontium isotopes in the carbonate precipitates, Foxe Basin Paleozoic bedrock, and local bedrock should define the source of the carbon and calcium in the deposits. Oxygen isotopes of Barnes Ice Cap Laurentide ice and the carbonates provide a unique opportunity to compare the isotopic composition of subglacial carbonates with the isotopic composition of the actual ice sheet under which they were precipitated.

Ice crystals classification using airborne measurements in mixing phase

NASA Astrophysics Data System (ADS)

Sorin Vajaiac, Nicolae; Boscornea, Andreea

2017-04-01

This paper presents a case study of ice crystals classification from airborne measurements in mixed-phase clouds. Ice crystal shadow is recorded with CIP (Cloud Imaging Probe) component of CAPS (Cloud, Aerosol, and Precipitation Spectrometer) system. The analyzed flight was performed in the south-western part of Romania (between Pietrosani, Ramnicu Valcea, Craiova and Targu Jiu), with a Beechcraft C90 GTX which was specially equipped with a CAPS system. The temperature, during the fly, reached the lowest value at -35 °C. These low temperatures allow the formation of ice crystals and influence their form. For the here presented ice crystals classification a special software, OASIS (Optical Array Shadow Imaging Software), developed by DMT (Droplet Measurement Technologies), was used. The obtained results, as expected are influenced by the atmospheric and microphysical parameters. The particles recorded where classified in four groups: edge, irregular, round and small.

Deposition of atmospheric heavy metals to the Greenland ice sheet from the 1783-1784 volcanic eruption of Laki, Iceland

NASA Astrophysics Data System (ADS)

Hong, Sungmin; Candelone, Jean-Pierre; Boutron, Claude F.

1996-11-01

In order to assess better the influence of major volcanic events on the large scale atmospheric cycles of heavy metals, Greenland ice dated from the time of the fallouts from the great 1783-1784 eruption of Laki volcano in Iceland has been analysed for Pb, Cd, Cu, Zn and sulphate. The concentrations of the four heavy metals investigated are found to be greatly enhanced in the ice layers which correspond to the fallouts from the eruption, confirming that such events do modify the atmospheric cycles of heavy metals. Cumulative fallout of heavy metals to the whole Greenland ice cap from the 1783-1784 Laki eruption ranges from 1 t for Pb and Cd to 40 t for Zn. For Cd, Cu and Zn, it represents a few percent of the cumulative anthropogenic fallout to the ice cap from the Industrial Revolution to the present.

A common and optimized age scale for Antarctic ice cores

NASA Astrophysics Data System (ADS)

Parrenin, F.; Veres, D.; Landais, A.; Bazin, L.; Lemieux-Dudon, B.; Toye Mahamadou Kele, H.; Wolff, E.; Martinerie, P.

2012-04-01

Dating ice cores is a complex problem because 1) there is a age shift between the gas bubbles and the surrounding ice 2) there are many different ice cores which can be synchronized with various proxies and 3) there are many methods to date the ice and the gas bubbles, each with advantages and drawbacks. These methods fall into the following categories: 1) Ice flow (for the ice) and firn densification modelling (for the gas bubbles); 2) Comparison of ice core proxies with insolation variations (so-called orbital tuning methods); 3) Comparison of ice core proxies with other well dated archives; 4) Identification of well-dated horizons, such as tephra layers or geomagnetic anomalies. Recently, an new dating tool has been developped (DATICE, Lemieux-Dudon et al., 2010), to take into account all the different dating information into account and produce a common and optimal chronology for ice cores with estimated confidence intervals. In this talk we will review the different dating information for Antarctic ice cores and show how the DATICE tool can be applied.

Mars Secular Obliquity Change Due to Water Ice Caps

NASA Technical Reports Server (NTRS)

Rubincam, David P.

1998-01-01

Mars may have substantially changed its average axial tilt over geologic time due to the waxing and waning of water ice caps. Depending upon Mars' climate and internal structure, the average obliquity could have increased or decreased through climate friction by tens of degrees. A decrease could account for the apparent youthfulness of the polar layered terrain. Alternatively, Mars' average obliquity may have changed until it became "stuck" at its present value of 24.4 deg.

Possible contemporary evaporites formation at the Martian Northern Polar Cap

NASA Astrophysics Data System (ADS)

Losiak, Anna; Czechowski, Leszek

Evaporitic minerals are abundant on the surface of Mars (e.g., Wentworth et al. 2005, Velbel 2012, Clark and Van Hart 1981, Wang et al. 2006, Kuzmin et al. 2009), especially within the Circumpolar Dune Field and on the Northern Ice Cap itself (e.g., Langevin et al., 2005, Roach et al. 2007, Horgan et al. 2009, Masse et al. 2010, 2012). Most of their proposed formation mechanisms require significant amounts of liquid water and are thus not possible under current Martian conditions (Arvidson et al. 2006, Andrews-Hanna et al. 2007, Fishbaugh et al. 2007, Szynkiewicz et al. 2010). Some authors have considered the potential role of ice and ice- or snowmelt-related alteration in the weathering of Martian materials (e.g., Catling et al. 2006, Zolotov and Mironenko 2007, Niles and Michalski 2009, Masse et al. 2010). However, none of those studies discussed details of the process leading to the formation of the evaporites or the timing of the processes. The aim of this paper is to model numerically if the current radiant heating is sufficient to melt a thin layer of ice surrounding a single dust grain exposed within the south facing side of the Martian North Polar Cap trench. The results of our initial study suggest that for dust grains with basaltic properties and ice with low values of coefficient of heat conduction, and solar constant = 492 W/m2 liquid water may exist below a dust grain for up to 4 hours a sol. This suggest that contemporary evaporites formation on Martian Polar Cap is possible.

A century of Amazon burning driven by Atlantic climate

NASA Astrophysics Data System (ADS)

Makou, M.; Thompson, L. G.; Davis, M. E.; Eglinton, T. I.

2011-12-01

Very little is known about annual burning trends in the Amazon Basin prior to remote sensing of fires beginning in the late 1970's. Fires reduce Amazon forest biomass and species richness, release pollutant aerosols, and impact the carbon cycle, compelling further investigation of fire-climate dynamics. We measured organic compounds derived from vegetation burning in ice core samples from the Quelccaya Ice Cap in Peru at better than annual resolution to reconstruct wet and dry season burning throughout the Twentieth Century. Variations in the abundance of methyl hexadecanoate, which is produced by thermal alteration of vascular plant alkanoic acids, were used as a proxy for past fire activity. Concentrations of this compound in Quelccaya ice varied strongly on seasonal, interannual, and decadal time scales over the last 100 years, with high-amplitude dry season variability and muted, decadal-scale changes in wet season fire activity. Decade-long periods of repeatedly enhanced burning occurred during the 1930's and 1960's when dry season precipitation was perpetually reduced, as evidenced by low stages of the Rio Negro. These decadal trends suggest that changes in dry season precipitation drive fire activity in the western Amazon and highlight the potential of Amazon forests to undergo repeated strong burning. Fires occurred during years when sea surface temperatures (SSTs) in the north tropical Atlantic were elevated and the north-south tropical Atlantic SST gradient was enhanced; this SST pattern likely displaced the intertropical convergence zone northward, driving subsidence and drought in the western and southern Amazon basin. Thus, our novel ice core record suggests that Amazon forest fire activity during the Twentieth Century was driven primarily by Atlantic climate processes, and future forest health will depend heavily on the evolution of tropical climate.

Volcano-ice interactions on Mars

NASA Technical Reports Server (NTRS)

Allen, C. C.

1979-01-01

Central volcanic eruptions beneath terrestrial glaciers have built steep-sided, flat-topped mountains composed of pillow lava, glassy tuff, capping flows, and cones of basalt. Subglacial fissure eruptions produced ridges of similar composition. In some places the products from a number of subglacial vents have combined to form widespread deposits. The morphologies of these subglacial volcanoes are distinctive enough to allow their recognition at the resolutions characteristic of Viking orbiter imagery. Analogs to terrestrial subglacial volcanoes have been identified on the northern plains and near the south polar cap of Mars. The polar feature provides probable evidence of volcanic eruptions beneath polar ice. A mixed unit of rock and ice is postulated to have overlain portions of the northern plains, with eruptions into this ground ice having produced mountains and ridges analogous to those in Iceland. Subsequent breakdown of this unit due to ice melting revealed the volcanic features. Estimated heights of these landforms indicate that the ice-rich unit once ranged from approximately 100 to 1200 m thick.

A Warmer Atmosphere on Mars near the Noachian-Hesperian Boundary: Evidence from Basal Melting of the South Polar Ice Cap (Dorsa Argentea Formation)

NASA Astrophysics Data System (ADS)

Fastook, J. L.; Head, J. W.; Marchant, D. R.; Forget, F.; Madeleine, J.-B.

2012-05-01

Eskers in the Dorsa Argentea Formation imply the presence of an ice sheet with a wet bed. With an ice sheet model, we examine a range of geothermal heat fluxes and warmer climates to determine what conditions could produce such an ice sheet.

Sensing the bed-rock movement due to ice unloading from space using InSAR time-series

NASA Astrophysics Data System (ADS)

Zhao, W.; Amelung, F.; Dixon, T. H.; Wdowinski, S.

2014-12-01

Ice-sheets in the Arctic region are retreating rapidly since late 1990s. Typical ice loss rates are 0.5 - 1 m/yr at the Canadian Arctic Archipelago, ~ 1 m/yr at the Icelandic ice sheets, and several meters per year at the edge of Greenland ice sheet. Such load decreasing causes measurable (several millimeter per year) deformation of the Earth's crust from Synthetic Aperture Radar Interferometry (InSAR). Using small baseline time-series analysis, this signal is retrieved after noises such as orbit error, atmospheric delay and DEM error being removed. We present results from Vatnajokull ice cap, Petermann glacier and Barnes ice cap using ERS, Envisat and TerraSAR-X data. Up to 2 cm/yr relative radar line-of-sight displacement is detected. The pattern of deformation matches the shape of ice sheet very well. The result in Iceland was used to develop a new model for the ice mass balance estimation from 1995 to 2010. Other applications of this kind of technique include validation of ICESat or GRACE based ice sheet model, Earth's rheology (Young's modulus, viscosity and so on). Moreover, we find a narrow (~ 1km) uplift zone close to the periglacial area of Petermann glacier which may due to a special rheology under the ice stream.

Abnormal Winter Melting of the Arctic Sea Ice Cap Observed by the Spaceborne Passive Microwave Sensors

NASA Astrophysics Data System (ADS)

Lee, Seongsuk; Yi, Yu

2016-12-01

The spatial size and variation of Arctic sea ice play an important role in Earth’s climate system. These are affected by conditions in the polar atmosphere and Arctic sea temperatures. The Arctic sea ice concentration is calculated from brightness temperature data derived from the Defense Meteorological Satellite program (DMSP) F13 Special Sensor Microwave/Imagers (SSMI) and the DMSP F17 Special Sensor Microwave Imager/Sounder (SSMIS) sensors. Many previous studies point to significant reductions in sea ice and their causes. We investigated the variability of Arctic sea ice using the daily sea ice concentration data from passive microwave observations to identify the sea ice melting regions near the Arctic polar ice cap. We discovered the abnormal melting of the Arctic sea ice near the North Pole during the summer and the winter. This phenomenon is hard to explain only surface air temperature or solar heating as suggested by recent studies. We propose a hypothesis explaining this phenomenon. The heat from the deep sea in Arctic Ocean ridges and/ or the hydrothermal vents might be contributing to the melting of Arctic sea ice. This hypothesis could be verified by the observation of warm water column structure below the melting or thinning arctic sea ice through the project such as Coriolis dataset for reanalysis (CORA).

Munc13 homology domain-1 in CAPS/UNC31 mediates SNARE binding required for priming vesicle exocytosis.

PubMed

Khodthong, Chuenchanok; Kabachinski, Greg; James, Declan J; Martin, Thomas F J

2011-08-03

Neuropeptide and peptide hormone secretion from neural and endocrine cells occurs by Ca(2+)-triggered dense-core vesicle exocytosis. The membrane fusion machinery consisting of vesicle and plasma membrane SNARE proteins needs to be assembled for Ca(2+)-triggered vesicle exocytosis. The related Munc13 and CAPS/UNC31 proteins that prime vesicle exocytosis are proposed to promote SNARE complex assembly. CAPS binds SNARE proteins and stimulates SNARE complex formation on liposomes, but the relevance of SNARE binding to CAPS function in cells had not been determined. Here we identify a core SNARE-binding domain in CAPS as corresponding to Munc13 homology domain-1 (MHD1). CAPS lacking a single helix in MHD1 was unable to bind SNARE proteins or to support the Ca(2+)-triggered exocytosis of either docked or newly arrived dense-core vesicles. The results show that MHD1 is a SNARE-binding domain and that SNARE protein binding is essential for CAPS function in dense-core vesicle exocytosis. Copyright © 2011 Elsevier Inc. All rights reserved.

Multi-MICE: Nuclear Powered Mobile Probes to Explore Deep Interiors of the Ice Sheets on Mars and the Jovian Moons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maise, George; Powell, James; Paniagua, John

2007-01-30

The multi-kilometer thick Polar Caps on Mars contain unique and important data about the multi-million year history of its climate, geology, meteorology, volcanology, cosmic ray and solar activity, and meteor impacts. They also may hold evidence of past life on Mars, including microbes, microfossils and biological chemicals. The objective of this paper is to describe a probe that can provide access to the data locked in the Polar Caps. The MICE (Mars Ice Cap Explorer) system would explore the Polar Cap interiors using mobile probes powered by compact, lightweight nuclear reactors. The probes would travel 100's of meters per daymore » along melt channels in the ice sheets created by hot water jets from the 500 kW(th) nuclear reactors, ascending and descending, either vertically or at an angle to the vertical, reaching bedrock at kilometers beneath the surface. The powerful reactor will be necessary to provide sufficient hot water at high velocity to penetrate the extensive horizontal dust/sand layers that separate layers of ice in the Mars Ice Caps. MICE reactors can operate at 500 kW(th) for more than 4 years, and much longer in practice, since power level will be much lower when the probes are investigating locations in detail at low or zero speed. Multiple probes, e.g. six, would be deployed in an interactive network, continuously communicating by RF and acoustic signals with each other and with the surface lander spacecraft. In turn, the lander would continuously communicate in real time, subject to speed of light delays, with scientists on Earth to transmit data and receive instructions for the MICE probes. Samples collected by the probes could be brought to the lander, for return to the Earth at the end of the mission.« less

The rapid formation of Sputnik Planitia early in Pluto's history.

PubMed

Hamilton, Douglas P; Stern, S A; Moore, J M; Young, L A

2016-11-30

Pluto's Sputnik Planitia is a bright, roughly circular feature that resembles a polar ice cap. It is approximately 1,000 kilometres across and is centred on a latitude of 25 degrees north and a longitude of 175 degrees, almost directly opposite the side of Pluto that always faces Charon as a result of tidal locking. One explanation for its location includes the formation of a basin in a giant impact, with subsequent upwelling of a dense interior ocean. Once the basin was established, ice would naturally have accumulated there. Then, provided that the basin was a positive gravity anomaly (with or without the ocean), true polar wander could have moved the feature towards the Pluto-Charon tidal axis, on the far side of Pluto from Charon. Here we report modelling that shows that ice quickly accumulates on Pluto near latitudes of 30 degrees north and south, even in the absence of a basin, because, averaged over its orbital period, those are Pluto's coldest regions. Within a million years of Charon's formation, ice deposits on Pluto concentrate into a single cap centred near a latitude of 30 degrees, owing to the runaway albedo effect. This accumulation of ice causes a positive gravity signature that locks, as Pluto's rotation slows, to a longitude directly opposite Charon. Once locked, Charon raises a permanent tidal bulge on Pluto, which greatly enhances the gravity signature of the ice cap. Meanwhile, the weight of the ice in Sputnik Planitia causes the crust under it to slump, creating its own basin (as has happened on Earth in Greenland). Even if the feature is now a modest negative gravity anomaly, it remains locked in place because of the permanent tidal bulge raised by Charon. Any movement of the feature away from 30 degrees latitude is countered by the preferential recondensation of ices near the coldest extremities of the cap. Therefore, our modelling suggests that Sputnik Planitia formed shortly after Charon did and has been stable, albeit gradually losing volume, over the age of the Solar System.

The rapid formation of Sputnik Planitia early in Pluto's history

NASA Astrophysics Data System (ADS)

Hamilton, Douglas P.; Stern, S. A.; Moore, J. M.; Young, L. A.; Binzel, R. P.; Buie, M. W.; Buratti, B. J.; Cheng, A. F.; Ennico, K.; Grundy, W. M.; Linscott, I. R.; McKinnon, W. B.; Olkin, C. B.; Reitsema, H. J.; Reuter, D. C.; Schenk, P.; Showalter, M. R.; Spencer, J. R.; Tyler, G. L.; Weaver, H. A.

2016-12-01

Pluto's Sputnik Planitia is a bright, roughly circular feature that resembles a polar ice cap. It is approximately 1,000 kilometres across and is centred on a latitude of 25 degrees north and a longitude of 175 degrees, almost directly opposite the side of Pluto that always faces Charon as a result of tidal locking. One explanation for its location includes the formation of a basin in a giant impact, with subsequent upwelling of a dense interior ocean. Once the basin was established, ice would naturally have accumulated there. Then, provided that the basin was a positive gravity anomaly (with or without the ocean), true polar wander could have moved the feature towards the Pluto-Charon tidal axis, on the far side of Pluto from Charon. Here we report modelling that shows that ice quickly accumulates on Pluto near latitudes of 30 degrees north and south, even in the absence of a basin, because, averaged over its orbital period, those are Pluto's coldest regions. Within a million years of Charon's formation, ice deposits on Pluto concentrate into a single cap centred near a latitude of 30 degrees, owing to the runaway albedo effect. This accumulation of ice causes a positive gravity signature that locks, as Pluto's rotation slows, to a longitude directly opposite Charon. Once locked, Charon raises a permanent tidal bulge on Pluto, which greatly enhances the gravity signature of the ice cap. Meanwhile, the weight of the ice in Sputnik Planitia causes the crust under it to slump, creating its own basin (as has happened on Earth in Greenland). Even if the feature is now a modest negative gravity anomaly, it remains locked in place because of the permanent tidal bulge raised by Charon. Any movement of the feature away from 30 degrees latitude is countered by the preferential recondensation of ices near the coldest extremities of the cap. Therefore, our modelling suggests that Sputnik Planitia formed shortly after Charon did and has been stable, albeit gradually losing volume, over the age of the Solar System.

Two Extreme Climate Events of the Last 1000 Years Recorded in Himalayan and Andean Ice Cores: Impacts on Humans

NASA Astrophysics Data System (ADS)

Thompson, L. G.; Mosley-Thompson, E. S.; Davis, M. E.; Kenny, D. V.; Lin, P.

2013-12-01

In the last few decades numerous studies have linked pandemic influenza, cholera, malaria, and viral pneumonia, as well as droughts, famines and global crises, to the El Niño-Southern Oscillation (ENSO). Two annually resolved ice core records, one from Dasuopu Glacier in the Himalaya and one from the Quelccaya Ice Cap in the tropical Peruvian Andes provide an opportunity to investigate these relationships on opposite sides of the Pacific Basin for the last 1000 years. The Dasuopu record provides an annual history from 1440 to 1997 CE and a decadally resolved record from 1000 to 1440 CE while the Quelccaya ice core provides annual resolution over the last 1000 years. Major ENSO events are often recorded in the oxygen isotope, insoluble dust, and chemical records from these cores. Here we investigate outbreaks of diseases, famines and global crises during two of the largest events recorded in the chemistry of these cores, particularly large peaks in the concentrations of chloride (Cl-) and fluoride (Fl-). One event is centered on 1789 to 1800 CE and the second begins abruptly in 1345 and tapers off after 1360 CE. These Cl- and F- peaks represent major droughts and reflect the abundance of continental atmospheric dust, derived in part from dried lake beds in drought stricken regions upwind of the core sites. For Dasuopu the likely sources are in India while for Quelccaya the sources would be the Andean Altiplano. Both regions are subject to drought conditions during the El Niño phase of the ENSO cycle. These two events persist longer (10 to 15 years) than today's typical ENSO events in the Pacific Ocean Basin. The 1789 to 1800 CE event was associated with a very strong El Niño event and was coincidental with the Boji Bara famine resulting from extended droughts that led to over 600,000 deaths in central India by 1792. Similarly extensive droughts are documented in Central and South America. Likewise, the 1345 to 1360 CE event, although poorly documented historically in South America, is concomitant with major droughts in India, the collapse of the Yang Dynasty and the Black Death that eliminated roughly one third of the global population. Understanding the characteristics and drivers of these 'natural' events is critical to design adaptive measures for a world with over seven billion people and a climate system now influenced by human activities.

Geophysical Investigations of Hypersaline Subglacial Water Systems in the Canadian Arctic: A Planetary Analog

NASA Astrophysics Data System (ADS)

Rutishauser, A.; Sharp, M. J.; Blankenship, D. D.; Skidmore, M. L.; Grima, C.; Schroeder, D. M.; Greenbaum, J. S.; Dowdeswell, J. A.; Young, D. A.

2017-12-01

Robotic exploration and remote sensing of the solar system have identified the presence of liquid water beneath ice on several planetary bodies, with evidence for elevated salinity in certain cases. Subglacial water systems beneath Earth's glaciers and ice sheets may provide terrestrial analogs for microbial habitats in such extreme environments, especially those with higher salinity. Geological data suggest that several ice caps and glaciers in the eastern Canadian High Arctic are partially underlain by evaporite-rich sedimentary rocks, and subglacial weathering of these rocks is potentially conducive to the formation of hypersaline subglacial waters. Here, we combine airborne geophysical data with geological constraints to identify and characterize hypersaline subglacial water systems beneath ice caps in Canada's Queen Elizabeth Islands. High relative bedrock reflectivity and specularity anomalies that are apparent in radio-echo sounding data indicate multiple locations where subglacial water is present in areas where modeled ice temperatures at the glacier bed are well below the pressure melting point. This suggests that these water systems are hypersaline, with solute concentrations that significantly depress the freezing point of water. From combined interpretations of geological and airborne-magnetic data, we define the geological context within which these systems have developed, and identify possible solute-sources for the inferred brine-rich water systems. We also derive subglacial hydraulic potential gradients using airborne laser altimetry and ice thickness data, and apply water routing models to derive subglacial drainage pathways. These allow us to identify marine-terminating glaciers where outflow of the brine-rich waters may be anticipated. These hypersaline subglacial water systems beneath Canadian Arctic ice caps and glaciers may represent robust microbial habitats, and potential analogs for brines that may exist beneath ice masses on planetary bodies elsewhere in the Solar System.

Seasonal speed-up of two outlet glaciers of Austfonna, Svalbard, inferred from continuous GPS measurements

NASA Astrophysics Data System (ADS)

Dunse, T.; Schuler, T. V.; Hagen, J. O.; Reijmer, C. H.

2011-12-01

A large part of the ice discharge from ice caps and ice sheets occurs through spatially limited flow units that may operate in a mode of steady flow or cyclic surge behaviour. Changes in the dynamics of distinct flow units play a key role in the mass balance of Austfonna, the largest ice cap on Svalbard. The recent net mass loss of Austfonna was dominated by calving from marine terminating outlet glaciers. Previous ice-surface velocity maps of the ice cap were derived by satellite radar interferometry (InSAR) and rely on data acquired in the mid-1990s with limited information concerning the temporal variability. Here, we present continuous Global Positioning System (GPS) observations along the central flowlines of two fast flowing outlet glaciers over 2008-2010. The data show prominent summer speed-ups with ice-surface velocities as high as 240 % of the pre-summer mean. Acceleration follows the onset of the summer melt period, indicating enhanced basal motion due to input of surface meltwater into the subglacial drainage system. In 2008, multiple velocity peaks coincide with successive melt periods. In 2009, the principle melt was of higher amplitude than in 2008. Flow velocities appear unaffected by subsequent melt periods, suggesting a transition towards a hydraulically more efficient drainage system. The observed annual mean velocities of Duvebreen and Basin-3 exceed those from the mid-1990s by factors two and four, respectively, implying increased ice discharge at the calving front. Measured summer velocities up to 2 m d-1 for Basin-3 are close to that of Kronebreen, often referred to as the fastest glacier on Svalbard.

IR spectral properties of dust and ice at the Mars south polar cap

NASA Astrophysics Data System (ADS)

Titus, T. N.; Kieffer, H. H.

2001-11-01

Removal of atmospheric dust effects is required to derive surface IR spectral emissivity. Commonly, the atmospheric-surface separation is based on radiative transfer (RT) spectral inversion methods using nadir-pointing observations. This methodology depends on a priori knowledge of the spectral shape of each atmospheric aerosol (e.g. dust or water ice) and a large thermal contrast between the surface and atmosphere. RT methods fail over the polar caps due to low thermal contrast between the atmosphere and the surface. We have used multi-angle Emission Phase Function (EPF) observations to estimate the opacity spectrum of dust over the springtime south polar cap and the underlying surface radiance, and thus, the surface emissivity. We include a few EPFs from Hellas Basin as a basis for comparisons between the spectral shape of polar and non-polar dust. Surface spectral emissivities over the seasonal cap are compared to CO2 models. Our results show that the spectral shape of the polar dust opacity is not constant, but is a two-parameter family that can be characterized by the 9 um and 20 um opacities. The 9 um opacity varies from 0.15 to 0.45 and characterizes the overall atmospheric conditions. The 9 um to 20 um opacity ratio varies from 2.0 to 5.1, suggesting changes in dust size distribution over the polar caps. Derived surface temperatures from the EPFs confirm that the slightly elevated temperatures (relative to CO2 frost temperature) observed in ``cryptic'' regions are a surface effect, not atmospheric. Comparison of broad-band reflectivity and surface emissivities to model spectra suggest the bright regions (e.g. perennial cap, Mountains of Mitchell) have higher albedos due to a thin surface layer of fine-grain CO2 (perhaps either frost or fractured ice) with an underlying layer of either coarse grain or slab CO2 ice.

Core to Atmosphere Exploration of Ice Giants: A Uranus Mission Concept Study

NASA Astrophysics Data System (ADS)

Jensema, R. J.; Arias-Young, T. M.; Wilkins, A. N.; Ermakov, A.; Bennett, C.; Dietrich, A.; Hemingway, D.; Klein, V.; Mane, P.; Marr, K. D.; Masterson, J.; Siegel, V.; Stober, K. J.; Talpe, M.; Vines, S. K.; Wetteland, C. J.

2014-12-01

Ice giants remain largely unexplored, as their large distance from the Sun limits both Earth-based observations and spacecraft visits. The significant occurrence of ice giant-sized planets among detected exoplanets presents an impetus to study Uranus to understand planetary formation, dynamics, and evolution. In addition, Uranus is also uniquely interesting, given the large inclination of its rotation axis and magnetospheric configuration. In this work, we design a mission concept that aims to maximize scientific return by measuring Uranus' chemical composition, internal structure, and magnetosphere, the first two being primary indicators of ice giant formation mechanisms. For this study, we analyze the trade space for a Uranus mission constrained by a cost cap of $1B. We discuss the decision making processes behind our choices of the science priorities, instrument suite and orbital configuration. Trade space decisions include a strong onboard instrument suite in lieu of a descent probe, an orbiter instead of a flyby mission, and design constraints on the power and propulsion systems. The mission, CAELUS (Core and Atmospheric Evolution Laboratory for Uranus Science), is designed for an August 2023 launch. Following a 14-year cruise with multiple planetary gravity assists, the spacecraft would begin its science mission, which consists of a series of ten 30-day near-polar orbits around Uranus. The instrument suite would consist of a microwave radiometer, Doppler seismometer, magnetometer, and UV spectrometer. These four instruments, along with a high-gain antenna capable of gravity science, would provide a comprehensive science return that meets the bulk of the scientific objectives of the 2013 NRC Planetary Science Decadal Survey for ice giants, most notably those regarding the chemical composition, interior structure, and dynamo of Uranus. This mission concept was created as part of an educational exercise for the 2014 Planetary Science Summer School at the Jet Propulsion Laboratory.

Orbitally-Induced, Quasi-Periodic Climate Change on Mars: Modelling Changes in the Global Cycling of Water and Carbon Dioxide

NASA Astrophysics Data System (ADS)

Mischna, M. A.; Richardson, M. I.; Wilson, R. J.

2002-12-01

Mars' orbital parameters (obliquity, eccentricity and argument of perihelion) are thought to have varied substantially on time scales >105 years. Such variations, especially in obliquity, may drastically affect the circulation of the atmosphere and volatile cycling. In this study, we focus on the response of the water and carbon dioxide cycles to changes in these orbital parameters, chiefly obliquity. The study employs the Geophysical Fluid Dynamics Laboratory Mars General Circulation Model, conducting simulations over a range of orbital states to examine changes in the cycling and deposition of these volatiles. This model contains full 3D accounting of atmospheric water and carbon dioxide as well as a basic dust cycle. The present martian obliquity is 25°, though it is believed to have recently varied between 15 and 45 degrees. Our simulations look at present martian conditions, only with obliquity varying between 5 and 60 degrees. Simulations are run out until water and carbon dioxide budgets have reached equilibrium--typically 30-40 years. As expected, volatile cycling on Mars increases with obliquity, as the polar caps are exposed to increased insolation, leading to greater seasonal ice caps and ultimately development of surface water ice in the now thermally favorible low latitudes. By 45°, water ice is stable in a broad band just north of the equator. Such an ice distribution has potential implications for the surface wind pattern through the ice-albedo effect on surface heating. Permanent polar CO2 caps are not stable under present conditions, but we find CO2 cap growth and corresponding atmospheric deflation to be evident at very low obliquities. We find that for most choices of orbital conditions, the northern hemisphere remains the stable pole for water ice, a result of the martian topographic dichotomy. We have begun to look at the impact of desorbed CO2 and H2O ice from the regolith on climatic conditions. Present estimates of the volatile abundance in the regolith vary greatly, but recent Mars Odyssey results hint at large abundances of water ice in the martian high-latitude regolith. The results of this study should better define models of polar volatile evolution, specifically those of layered terrain formation. The radiative feedback effects of increased atmospheric CO2 and H2O from the polar caps and regoliths has yet to be examined. Future plans include more accurate representations of dust injection and radiative transfer to tackle this problem.

Resident CAPS on dense-core vesicles docks and primes vesicles for fusion.

PubMed

Kabachinski, Greg; Kielar-Grevstad, D Michelle; Zhang, Xingmin; James, Declan J; Martin, Thomas F J

2016-02-15

The Ca(2+)-dependent exocytosis of dense-core vesicles in neuroendocrine cells requires a priming step during which SNARE protein complexes assemble. CAPS (aka CADPS) is one of several factors required for vesicle priming; however, the localization and dynamics of CAPS at sites of exocytosis in live neuroendocrine cells has not been determined. We imaged CAPS before, during, and after single-vesicle fusion events in PC12 cells by TIRF micro-scopy. In addition to being a resident on cytoplasmic dense-core vesicles, CAPS was present in clusters of approximately nine molecules near the plasma membrane that corresponded to docked/tethered vesicles. CAPS accompanied vesicles to the plasma membrane and was present at all vesicle exocytic events. The knockdown of CAPS by shRNA eliminated the VAMP-2-dependent docking and evoked exocytosis of fusion-competent vesicles. A CAPS(ΔC135) protein that does not localize to vesicles failed to rescue vesicle docking and evoked exocytosis in CAPS-depleted cells, showing that CAPS residence on vesicles is essential. Our results indicate that dense-core vesicles carry CAPS to sites of exocytosis, where CAPS promotes vesicle docking and fusion competence, probably by initiating SNARE complex assembly. © 2016 Kabachinski, Kielar-Grevstad, et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

A late Holocene metal record of Andean climate and anthropogenic activity in lake sediments near Quelccaya Ice Cap, Peru

NASA Astrophysics Data System (ADS)

Beal, S. A.; Kelly, M. A.; Jackson, B. P.; Stroup, J. S.; Osterberg, E. C.

2011-12-01

The tropical hypothesis maintains that major changes in global climate are motivated by phenomena based at tropical latitudes. Evidence for this hypothesis lies in: modern-day observations of El Niño Southern Oscillation (ENSO); East African lake sediment records of Intertropical Convergence Zone (ITCZ) position that precede high-latitude changes; and the potential for ITCZ shifts to cause major CO2 degassing from the Southern Ocean. In order to improve the understanding of these phenomena we present an ~1800 year record of atmospheric metal deposition in a lake sediment core near Quelccaya Ice Cap, Peru (13.9 °S). In June, 2010 we collected a 1.45 meter-long core from Yanacocha - a small, closed-basin tarn that has been isolated from glacial input since ~11,200 BP. The chronology for the core is based on 4 of 6 AMS 14C dates on aquatic macrofossils and one sharp Zr/Ti anomaly at 36 cm, likely derived from the 350 BP eruption of Huaynaputina. We completely digested organic-rich core samples at 1 cm resolution using HNO3, HCl, and HF in a closed-vessel microwave system, and then analyzed the digestates for 67 metals by inductively coupled plasma mass spectrometry. Here we show fluxes of lithogenic metals (Fe, Nb, Ti, and Zr) that reflect changes in wind strength and aridity, fluxes of lithogenic metal isotopes (REEs and Pb) that reflect wind direction, and enrichment factors (EFs) of metals (Ag, As, Cd, Cu, Hg, and Pb) that reflect anthropogenic activity. Five episodic peaks in lithogenic metal fluxes, centered around 1800, 1300, 900, 600, and 100 yrs BP, are thought to result from either drier or windier conditions, potentially caused by a northern ITCZ position or a more persistent El Niño state. The provenance of atmospheric deposition, evidenced by REE ratios (light REEs / heavy REEs), suggest that high lithogenic fluxes are associated with a change in wind direction, possibly caused by a change in the ENSO state, which will be explored with forthcoming Pb isotope data. Metals commonly associated with mining and ore-processing become unnaturally enriched (EF > 2) during times of low lithogenic metal fluxes, suggesting a strong tie between climatic conditions and the activity of ancient civilizations in the Andes.

Atmospheric precursors of and response to anomalous Arctic sea ice in CMIP5 models

NASA Astrophysics Data System (ADS)

Kelleher, Michael; Screen, James

2018-01-01

This study examines pre-industrial control simulations from CMIP5 climate models in an effort to better understand the complex relationships between Arctic sea ice and the stratosphere, and between Arctic sea ice and cold winter temperatures over Eurasia. We present normalized regressions of Arctic sea-ice area against several atmospheric variables at extended lead and lag times. Statistically significant regressions are found at leads and lags, suggesting both atmospheric precursors of, and responses to, low sea ice; but generally, the regressions are stronger when the atmosphere leads sea ice, including a weaker polar stratospheric vortex indicated by positive polar cap height anomalies. Significant positive midlatitude eddy heat flux anomalies are also found to precede low sea ice. We argue that low sea ice and raised polar cap height are both a response to this enhanced midlatitude eddy heat flux. The so-called "warm Arctic, cold continents" anomaly pattern is present one to two months before low sea ice, but is absent in the months following low sea ice, suggesting that the Eurasian cooling and low sea ice are driven by similar processes. Lastly, our results suggest a dependence on the geographic region of low sea ice, with low Barents-Kara Sea ice correlated with a weakened polar stratospheric vortex, whilst low Sea of Okhotsk ice is correlated with a strengthened polar vortex. Overall, the results support a notion that the sea ice, polar stratospheric vortex and Eurasian surface temperatures collectively respond to large-scale changes in tropospheric circulation.

Environmental Effects on Volcanic Eruptions:From Deep Ocean to Deep Space. Chapter 3. Volcanism and Ice Interactions on Earth and Mars. Chapter 3

NASA Technical Reports Server (NTRS)

Chapman, Mary G.; Allen, Carlton C.; Gudmundsson, Magnus T.; Gulick, Virginia C.; Jakobsson, Sveinn P.; Lucchitta, Baerbel K.; Skilling, Ian P.; Waitt, Richard B.

2000-01-01

CONCLUSION Volcano/ice interactions produce meltwater. Meltwater can enter the groundwater cycle and under the influence of hydrothermal systems, it can be later discharged to form channels and valleys or cycled upward to melt permafrost. Water or ice-saturated ground can erupt into phreatic craters when covered by lava. Violent mixing of meltwater and volcanic material and rapid release can generate lahars or jokulhlaups, that have the ability to freight coarse material, great distances downslope from the vent. Eruption into meltwater generate unique appearing edifices, that are definitive indicators of volcano/ice interaction. These features are hyaloclastic ridges or mounds and if capped by lava, tuyas. On Earth, volcano/ice interactions are limited to alpine regions and ice-capped polar and temperate regions. On Mars, where precipitation may be an ancient phenomenon, these interactions may be limited to areas of ground ice accumulation or the northern lowlands where water may have ponded fairly late in martian history. The recognition of features caused by volcano/ice interactions could provide strong constraints for the history of volatiles on Mars.

IceChrono1: a probabilistic model to compute a common and optimal chronology for several ice cores

NASA Astrophysics Data System (ADS)

Parrenin, F.; Bazin, L.; Capron, E.; Landais, A.; Lemieux-Dudon, B.; Masson-Delmotte, V.

2015-05-01

Polar ice cores provide exceptional archives of past environmental conditions. The dating of ice cores and the estimation of the age-scale uncertainty are essential to interpret the climate and environmental records that they contain. It is, however, a complex problem which involves different methods. Here, we present IceChrono1, a new probabilistic model integrating various sources of chronological information to produce a common and optimized chronology for several ice cores, as well as its uncertainty. IceChrono1 is based on the inversion of three quantities: the surface accumulation rate, the lock-in depth (LID) of air bubbles and the thinning function. The chronological information integrated into the model are models of the sedimentation process (accumulation of snow, densification of snow into ice and air trapping, ice flow), ice- and air-dated horizons, ice and air depth intervals with known durations, depth observations (depth shift between synchronous events recorded in the ice and in the air) and finally air and ice stratigraphic links in between ice cores. The optimization is formulated as a least squares problem, implying that all densities of probabilities are assumed to be Gaussian. It is numerically solved using the Levenberg-Marquardt algorithm and a numerical evaluation of the model's Jacobian. IceChrono follows an approach similar to that of the Datice model which was recently used to produce the AICC2012 (Antarctic ice core chronology) for four Antarctic ice cores and one Greenland ice core. IceChrono1 provides improvements and simplifications with respect to Datice from the mathematical, numerical and programming point of views. The capabilities of IceChrono1 are demonstrated on a case study similar to the AICC2012 dating experiment. We find results similar to those of Datice, within a few centuries, which is a confirmation of both IceChrono1 and Datice codes. We also test new functionalities with respect to the original version of Datice: observations as ice intervals with known durations, correlated observations, observations as air intervals with known durations and observations as mixed ice-air stratigraphic links. IceChrono1 is freely available under the General Public License v3 open source license.

A Mars Sample Return Sample Handling System

NASA Technical Reports Server (NTRS)

Wilson, David; Stroker, Carol

2013-01-01

We present a sample handling system, a subsystem of the proposed Dragon landed Mars Sample Return (MSR) mission [1], that can return to Earth orbit a significant mass of frozen Mars samples potentially consisting of: rock cores, subsurface drilled rock and ice cuttings, pebble sized rocks, and soil scoops. The sample collection, storage, retrieval and packaging assumptions and concepts in this study are applicable for the NASA's MPPG MSR mission architecture options [2]. Our study assumes a predecessor rover mission collects samples for return to Earth to address questions on: past life, climate change, water history, age dating, understanding Mars interior evolution [3], and, human safety and in-situ resource utilization. Hence the rover will have "integrated priorities for rock sampling" [3] that cover collection of subaqueous or hydrothermal sediments, low-temperature fluidaltered rocks, unaltered igneous rocks, regolith and atmosphere samples. Samples could include: drilled rock cores, alluvial and fluvial deposits, subsurface ice and soils, clays, sulfates, salts including perchlorates, aeolian deposits, and concretions. Thus samples will have a broad range of bulk densities, and require for Earth based analysis where practical: in-situ characterization, management of degradation such as perchlorate deliquescence and volatile release, and contamination management. We propose to adopt a sample container with a set of cups each with a sample from a specific location. We considered two sample cups sizes: (1) a small cup sized for samples matching those submitted to in-situ characterization instruments, and, (2) a larger cup for 100 mm rock cores [4] and pebble sized rocks, thus providing diverse samples and optimizing the MSR sample mass payload fraction for a given payload volume. We minimize sample degradation by keeping them frozen in the MSR payload sample canister using Peltier chip cooling. The cups are sealed by interference fitted heat activated memory alloy caps [5] if the heating does not affect the sample, or by crimping caps similar to bottle capping. We prefer cap sealing surfaces be external to the cup rim to prevent sample dust inside the cups interfering with sealing, or, contamination of the sample by Teflon seal elements (if adopted). Finally the sample collection rover, or a Fetch rover, selects cups with best choice samples and loads them into a sample tray, before delivering it to the Earth Return Vehicle (ERV) in the MSR Dragon capsule as described in [1] (Fig 1). This ensures best use of the MSR payload mass allowance. A 3 meter long jointed robot arm is extended from the Dragon capsule's crew hatch, retrieves the sample tray and inserts it into the sample canister payload located on the ERV stage. The robot arm has capacity to obtain grab samples in the event of a rover failure. The sample canister has a robot arm capture casting to enable capture by crewed or robot spacecraft when it returns to Earth orbit

Temporal constraints on future accumulation-area loss of a major Arctic ice cap due to climate change (Vestfonna, Svalbard)

PubMed Central

Möller, Marco; Schneider, Christoph

2015-01-01

Arctic glaciers and ice caps are major contributors to past, present and future sea-level fluctuations. Continued global warming may eventually lead to the equilibrium line altitudes of these ice masses rising above their highest points, triggering unstoppable downwasting. This may feed future sea-level rise considerably. We here present projections for the timing of equilibrium-line loss at the major Arctic ice cap Vestfonna, Svalbard. The projections are based on spatially distributed climatic mass balance modelling driven by the outputs of multiple climate models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) forced by the Representative Concentration Pathways (RCPs) 2.6, 4.5, 6.0 and 8.5. Results indicate strongly decreasing climatic mass balances over the 21st century for all RCPs considered. Glacier-wide mass-balance rates will drop down to −4 m a−1 w.e. (water equivalent) at a maximum. The date at which the equilibrium line rises above the summit of Vestfonna (630 m above sea level) is calculated to range between 2040 and 2150, depending on scenario. PMID:25628045

Energetic Charged Particle Component or the NO(y) Budget of the Polar Middle Atmosphere

NASA Technical Reports Server (NTRS)

Vitt, F. M.; Jackman, C. H.

1999-01-01

Analysis of nitrates measured in polar ice cap snow at a high resolution shows large variations in the nitrates. It has been shown that the nitrate signal may contain a signature of solar activity [Zeller and Dreschhoff, 19951. Reactive odd nitrogen production associated with solar particle events (SPEs) and auroral activity may be a source of some of the nitrate anomalies observed in the polar ice caps. Periods of large SPEs can lead to a production of polar atmospheric odd nitrogen in excess of the ambient sources in the polar stratosphere and mesosphere, and may leave a large nitrate signal stratified in the polar ice cap. Auroral electrons and photoelectrons produce odd nitrogen in the thermosphere, some of which may be transported to the polar (>50 degrees) mesosphere and stratosphere. Sources of odd nitrogen in the polar middle atmosphere associated with SPEs, galactic cosmic rays, and auroral electron precipitation have been quantified. The relative contributions by the energetic particles sources to the Noy budget of the polar middle atmosphere (from tropopause to 50 km, from 50 degrees to 90 degrees latitude) are compared with the nitrates observed in the polar ice sheets.

Differences in Bacterial Diversity and Communities Between Glacial Snow and Glacial Soil on the Chongce Ice Cap, West Kunlun Mountains.

PubMed

Yang, Guang Li; Hou, Shu Gui; Le Baoge, Ri; Li, Zhi Guo; Xu, Hao; Liu, Ya Ping; Du, Wen Tao; Liu, Yong Qin

2016-11-04

A detailed understanding of microbial ecology in different supraglacial habitats is important due to the unprecedented speed of glacier retreat. Differences in bacterial diversity and community structure between glacial snow and glacial soil on the Chongce Ice Cap were assessed using 454 pyrosequencing. Based on rarefaction curves, Chao1, ACE, and Shannon indices, we found that bacterial diversity in glacial snow was lower than that in glacial soil. Principal coordinate analysis (PCoA) and heatmap analysis indicated that there were major differences in bacterial communities between glacial snow and glacial soil. Most bacteria were different between the two habitats; however, there were some common bacteria shared between glacial snow and glacial soil. Some rare or functional bacterial resources were also present in the Chongce Ice Cap. These findings provide a preliminary understanding of the shifts in bacterial diversity and communities from glacial snow to glacial soil after the melting and inflow of glacial snow into glacial soil.

The Effect of CO2 Ice Cap Sublimation on Mars Atmosphere

NASA Technical Reports Server (NTRS)

Batterson, Courtney

2016-01-01

Sublimation of the polar CO2 ice caps on Mars is an ongoing phenomenon that may be contributing to secular climate change on Mars. The transfer of CO2 between the surface and atmosphere via sublimation and deposition may alter atmospheric mass such that net atmospheric mass is increasing despite seasonal variations in CO2 transfer. My study builds on previous studies by Kahre and Haberle that analyze and compare data from the Phoenix and Viking Landers 1 and 2 to determine whether secular climate change is happening on Mars. In this project, I use two years worth of temperature, pressure, and elevation data from the MSL Curiosity rover to create a program that allows for successful comparison of Curiosity pressure data to Viking Lander pressure data so a conclusion can be drawn regarding whether CO2 ice cap sublimation is causing a net increase in atmospheric mass and is thus contributing to secular climate change on Mars.

Deep Radiostratigraphy of the East Antarctic Plateau: Connecting the Dome C and Vostok Ice Core Sites

NASA Technical Reports Server (NTRS)

Cavitte, Marie G. P.; Blankenship, Donald D.; Young, Duncan A.; Schroeder, Dustin M.; Parrenin, Frederic; Lemeur, Emmanuel; Macgregor, Joseph A.; Siegert, Martin J.

2016-01-01

Several airborne radar-sounding surveys are used to trace internal reflections around the European Project for Ice Coring in Antarctica Dome C and Vostok ice core sites. Thirteen reflections, spanning the last two glacial cycles, are traced within 200 km of Dome C, a promising region for million-year-old ice, using the University of Texas Institute for Geophysics High-Capacity Radar Sounder. This provides a dated stratigraphy to 2318 m depth at Dome C. Reflection age uncertainties are calculated from the radar range precision and signal-to-noise ratio of the internal reflections. The radar stratigraphy matches well with the Multichannel Coherent Radar Depth Sounder (MCoRDS) radar stratigraphy obtained independently. We show that radar sounding enables the extension of ice core ages through the ice sheet with an additional radar-related age uncertainty of approximately 1/3-1/2 that of the ice cores. Reflections are extended along the Byrd-Totten Glacier divide, using University of Texas/Technical University of Denmark and MCoRDS surveys. However, core-to-core connection is impeded by pervasive aeolian terranes, and Lake Vostok's influence on reflection geometry. Poor radar connection of the two ice cores is attributed to these effects and suboptimal survey design in affected areas. We demonstrate that, while ice sheet internal radar reflections are generally isochronal and can be mapped over large distances, careful survey planning is necessary to extend ice core chronologies to distant regions of the East Antarctic ice sheet.

Diatoms as Proxies for a Fluctuating Ice Cap Margin, Hvitarvatn, Iceland

NASA Astrophysics Data System (ADS)

Black, J. L.; Miller, G. H.; Geirsdottir, A.

2005-12-01

There are no complete records of terrestrial environmental change for the Holocene (11,000yrs) in Iceland and the status of Icelandic glaciers in the early Holocene remains unclear. It is not even known whether Iceland's large ice caps disappeared in the early Holocene, and if they did, when they re-grew. Icelandic lakes are particularly well suited to address these uncertainties as: 1) Glacial erosion and soft bedrock result in high lacustrine sedimentation rates, 2) Diagnostic tephras aid the geochronology, 3) Iceland's sensitivity to changes in North Atlantic circulation should produce clear signals in key environmental proxies (diatoms) preserved in lacustrine sequences, and 4) Ice-cap profiles are relatively flat so small changes in the equilibrium line altitude result in large changes in accumulation area. Hence, large changes in ice-sheet margins during the Holocene will impact sedimentation in glacier-dominated lakes and the diatom assemblages at those times. Hvitarvatn is a glacier dominated lake located on the eastern margin of Langjokull Ice Cap in central-western Iceland. The uppermost Hvitarvatn sediments reflect a glacially dominated system with planktonic, silica-demanding diatom taxa that suggest a high dissolved silica and turbid water environment consistent with high fluxes of glacial flour. Below this are Neoglacial sediments deposited when Langjokull was active, but outlet glaciers were not in contact with Hvitarvatn. The diatom assemblage here shows a small increase in abundance, but is still dominated by planktic, silica-demanding taxa. A distinct shift in lake conditions is reflected in the lowermost sediments, composed of predominantly benthic diatoms and deposited in clear water conditions with long growing seasons likely found in an environment with warmer summers than present and with no glacial erosion. Langjokull must have disappeared in the early Holocene for such a diverse, benthic dominated diatom assemblage to flourish.

Participation of D.O. Muhleman as a Co-Investigator on the Mars Observer Laser Altimeter (MOLA) Team

NASA Technical Reports Server (NTRS)

Muhleman, Duane O.

2004-01-01

The Co-I has been a principle member of the MOLA Team since the beginning of the Mars Observer Project and the MOLA Team formation. The basic area of research for the Co-I involved the interactions of the MOLA laser beam with the Mars atmosphere, ice fields and surface in general. The Co-I was assisted by one graduate student, and later a research assistant, Anton Ivanov, throughout the reporting period. Dr. Ivanov received a PhD from Caltech in 2000 from research involving the MOLA project. Dr. Ivanov continued with the MOLA project after receiving his degree as a research assistant to Professor Muhleman. Most of the funding from this grant was used to support Dr. Ivanov during the later years. The primary results of these investigations included the measurement of Mars atmospheric opacity at the 1 micron wavelength of the laser, the effects of dust within the craters and canyons of Mars, and a detailed study of the North Polar Ice Cap in terms of ice sublimation and the current structure of that ice cap. We were able to show that the sublimation of the ice on the polar cap would create the current average shape of the norther cap. Extensive data collection and study were made of the Mars surface 1 micron reflectivity until the laser mechanically failed during the reporting period. Reflectivity maps of Mars were produced although there were serious problems of the laser echo signal strength calibration. After that event the efforts were mainly to complete the older investigations. All of the work supported by this grant was theoretical in nature and did not lead to any patents.

Toward an integrated ice core chronology using relative and orbital tie-points

NASA Astrophysics Data System (ADS)

Bazin, L.; Landais, A.; Lemieux-Dudon, B.; Toyé Mahamadou Kele, H.; Blunier, T.; Capron, E.; Chappellaz, J.; Fischer, H.; Leuenberger, M.; Lipenkov, V.; Loutre, M.-F.; Martinerie, P.; Parrenin, F.; Prié, F.; Raynaud, D.; Veres, D.; Wolff, E.

2012-04-01

Precise ice cores chronologies are essential to better understand the mechanisms linking climate change to orbital and greenhouse gases concentration forcing. A tool for ice core dating (DATICE [developed by Lemieux-Dudon et al., 2010] permits to generate a common time-scale integrating relative and absolute dating constraints on different ice cores, using an inverse method. Nevertheless, this method has only been applied for a 4-ice cores scenario and for the 0-50 kyr time period. Here, we present the bases for an extension of this work back to 800 ka using (1) a compilation of published and new relative and orbital tie-points obtained from measurements of air trapped in ice cores and (2) an adaptation of the DATICE inputs to 5 ice cores for the last 800 ka. We first present new measurements of δ18Oatm and δO2/N2 on the Talos Dome and EPICA Dome C (EDC) ice cores with a particular focus on Marine Isotopic Stages (MIS) 5, and 11. Then, we show two tie-points compilations. The first one is based on new and published CH4 and δ18Oatm measurements on 5 ice cores (NorthGRIP, EPICA Dronning Maud Land, EDC, Talos Dome and Vostok) in order to produce a table of relative gas tie-points over the last 400 ka. The second one is based on new and published records of δO2/N2, δ18Oatm and air content to provide a table of orbital tie-points over the last 800 ka. Finally, we integrate the different dating constraints presented above in the DATICE tool adapted to 5 ice cores to cover the last 800 ka and show how these constraints compare with the established gas chronologies of each ice core.

Historical Isotopic Temperature Record from the Vostok Ice Core (420,000 years BP-present)

DOE Data Explorer

Petit, J. R. [Laboratoire de Glaciogie et Geophysique de l'Environnement; Raynaud, D. [Laboratoire de Glaciogie et Geophysique de l'Environnement; Lorius, C. [Laboratoire de Glaciogie et Geophysique de l'Environnement; Jouzel, J. [Laboratoire des Sciences du Climat et de l'Environnement; Delaygue, G. [Laboratoire des Sciences du Climat et de l'Environnement; Barkov, N. I. [Arctic and Antarctic Research Inst. (AARI), St. Petersburg (Russian Federation); Kotlyakov, V. M. [Institute of Geography, Russia

2000-01-01

Because isotopic fractions of the heavier oxygen-18 (18O) and deuterium (D) in snowfall are temperature-dependent and a strong spatial correlation exists between the annual mean temperature and the mean isotopic ratio (18O or δD) of precipitation, it is possible to derive ice-core climate records. The record presented by Jouzel et al. (1987) was the first ice core record to span a full glacial-interglacial cycle. That record was based on an ice core drilled at the Russian Vostok station in central east Antarctica. The 2083-m ice core was obtained during a series of drillings in the early 1970s and 1980s and was the result of collaboration between French and former-Soviet scientists. Drilling continued at Vostok and was completed in January 1998, reaching a depth of 3623 m, the deepest ice core ever recovered (Petit et al. 1997, 1999). The resulting core allows the ice core record of climate properties at Vostok to be extended to ~420 kyr BP.

A review of sea ice proxy information from polar ice cores

NASA Astrophysics Data System (ADS)

Abram, Nerilie J.; Wolff, Eric W.; Curran, Mark A. J.

2013-11-01

Sea ice plays an important role in Earth's climate system. The lack of direct indications of past sea ice coverage, however, means that there is limited knowledge of the sensitivity and rate at which sea ice dynamics are involved in amplifying climate changes. As such, there is a need to develop new proxy records for reconstructing past sea ice conditions. Here we review the advances that have been made in using chemical tracers preserved in ice cores to determine past changes in sea ice cover around Antarctica. Ice core records of sea salt concentration show promise for revealing patterns of sea ice extent particularly over glacial-interglacial time scales. In the coldest climates, however, the sea salt signal appears to lose sensitivity and further work is required to determine how this proxy can be developed into a quantitative sea ice indicator. Methane sulphonic acid (MSA) in near-coastal ice cores has been used to reconstruct quantified changes and interannual variability in sea ice extent over shorter time scales spanning the last ˜160 years, and has potential to be extended to produce records of Antarctic sea ice changes throughout the Holocene. However the MSA ice core proxy also requires careful site assessment and interpretation alongside other palaeoclimate indicators to ensure reconstructions are not biased by non-sea ice factors, and we summarise some recommended strategies for the further development of sea ice histories from ice core MSA. For both proxies the limited information about the production and transfer of chemical markers from the sea ice zone to the Antarctic ice sheets remains an issue that requires further multidisciplinary study. Despite some exploratory and statistical work, the application of either proxy as an indicator of sea ice change in the Arctic also remains largely unknown. As information about these new ice core proxies builds, so too does the potential to develop a more comprehensive understanding of past changes in sea ice and its role in both long and short-term climate changes.

Signs of a Martian Ice Age

NASA Image and Video Library

2016-05-26

This image montage features a two-dimensional radar cross section of Mars north polar cap collected by SHARAD instrument on NASA Mars Reconnaissance Orbiter spacecraft top, and a color image mosaic of the polar cap from NASA Viking project bottom

Modelling West Antarctic ice sheet growth and collapse through the past five million years.

PubMed

Pollard, David; DeConto, Robert M

2009-03-19

The West Antarctic ice sheet (WAIS), with ice volume equivalent to approximately 5 m of sea level, has long been considered capable of past and future catastrophic collapse. Today, the ice sheet is fringed by vulnerable floating ice shelves that buttress the fast flow of inland ice streams. Grounding lines are several hundred metres below sea level and the bed deepens upstream, raising the prospect of runaway retreat. Projections of future WAIS behaviour have been hampered by limited understanding of past variations and their underlying forcing mechanisms. Its variation since the Last Glacial Maximum is best known, with grounding lines advancing to the continental-shelf edges around approximately 15 kyr ago before retreating to near-modern locations by approximately 3 kyr ago. Prior collapses during the warmth of the early Pliocene epoch and some Pleistocene interglacials have been suggested indirectly from records of sea level and deep-sea-core isotopes, and by the discovery of open-ocean diatoms in subglacial sediments. Until now, however, little direct evidence of such behaviour has been available. Here we use a combined ice sheet/ice shelf model capable of high-resolution nesting with a new treatment of grounding-line dynamics and ice-shelf buttressing to simulate Antarctic ice sheet variations over the past five million years. Modelled WAIS variations range from full glacial extents with grounding lines near the continental shelf break, intermediate states similar to modern, and brief but dramatic retreats, leaving only small, isolated ice caps on West Antarctic islands. Transitions between glacial, intermediate and collapsed states are relatively rapid, taking one to several thousand years. Our simulation is in good agreement with a new sediment record (ANDRILL AND-1B) recovered from the western Ross Sea, indicating a long-term trend from more frequently collapsed to more glaciated states, dominant 40-kyr cyclicity in the Pliocene, and major retreats at marine isotope stage 31 ( approximately 1.07 Myr ago) and other super-interglacials.

Putting Radioactive Wastes on Ice: A Proposal for an International Radionuclide Depository in Antarctica

ERIC Educational Resources Information Center

Zeller, E. J.; And Others

1973-01-01

Describes need for creating permanent disposal of high-level radioactive wastes accumulating in different countries. Possibilities of establishing facilities for this purpose in Antarctic ice cap are examined. (PS)

Formation of Gas Traps in the Martian Soil and Implications for Methane Variability on Mars.

NASA Astrophysics Data System (ADS)

Pavlov, A.; Davis, J.; Redwing, E.; Trainer, M. G.; Johnson, C.

2017-12-01

Several independent groups have reported on the detection of methane in the Martian atmosphere. Mars Science Laboratory (MSL) methane observations display rapid increase of the atmospheric methane abundance from 1 ppb to 7 ppb levels followed by an abrupt disappearance suggest the possibility of small, local, near-surface sources of methane. Such sources may take the form of shallow subsurface cemented soil caps which can trap gases and are readily activated by either motion of the MSL rover itself, by impacts of small meteorites, or even annual climate oscillations. We have simulated the formation of such soil caps in the shallow subsurface Martian-like condition. We show that the initially uniform sample of icy soil (JSC-Mars-1A) with Mg perchlorate exhibit quick stratification on the scale of several cm under Martian pressures over the period of several days. Briny water migrates towards the top of the sample resulting in the enhanced abundance of perchlorates in the top few cm. As water evaporates and ice sublimates from the top of the sample, perchlorate remains in the top layer of soil causing soil cementation and formation of the cap. The observed caps were solid, ice-free and effectively shut off sublimation of ice from underneath the cap. We tested whether similar soil caps can trap various gases (including methane) in the shallow subsurface of Mars. We injected neon gas at the bottom of the soil sample and monitored neon gas permeability through the soil sample by measuring gas pressure differential above and below the soil sample. We found that a mixture of JSC-Mars-1A and 5% of Mg perchlorate produce gas impermeable soil cap capable of withstanding an excess of 5 mbars of neon under the cap at the soil temperatures +0.5 C - +9 C. The cap remained gas impermeable after subsequent cooling of the sample soil sample to the subzero temperatures. Gas permeability of the soil caps under various temperatures and atmospheric pressures will be reported. Our results suggest that the formation of cemented soil caps can be widespread phenomena on Mars in the areas of shallow permafrost and abundant perchlorates or RSL slopes. Potentially, soil caps can form gas pockets for trace species (like methane) which can be relatively easily disturbed causing abrupt changes in the atmospheric methane abundance detected by MSL's Curiosity rover.

Tracking the Martian CO2 Polar Ice Caps in Infrared Images

NASA Technical Reports Server (NTRS)

Wagstaff, Kiri L.; Castano, Rebecca; Chien, Steve

2006-01-01

Researchers at NASA s Jet Propulsion Laboratory have developed a method for automatically tracking the polar caps on Mars as they advance and recede each year (see figure). The seasonal Mars polar caps are composed mainly of CO2 ice and are therefore cold enough to stand out clearly in infrared data collected by the Thermal Emission Imaging System (THEMIS) onboard the Mars Odyssey spacecraft. The Bimodal Image Temperature (BIT) histogram analysis algorithm analyzes raw, uncalibrated data to identify images that contain both "cold" ("polar cap") and "warm" ("not polar cap") pixels. The algorithm dynamically identifies the temperature that separates these two regions. This flexibility is critical, because in the absence of any calibration, the threshold temperature can vary significantly from image to image. Using the identified threshold, the algorithm classifies each pixel in the image as "polar cap" or "not polar cap," then identifies the image row that contains the spatial transition from "polar cap" to "not polar cap." While this method is useful for analyzing data that has already been returned by THEMIS, it has even more significance with respect to data that has not yet been collected. Instead of seeking the polar cap only in specific, targeted images, the simplicity and efficiency of this method makes it feasible for direct, onboard use. That is, THEMIS could continuously monitor its observations for any detections of the polar-cap edge, producing detections over a wide range of spatial and temporal conditions. This effort can greatly contribute to our understanding of long-term climatic change on Mars.

Short-term sea ice forecasting: An assessment of ice concentration and ice drift forecasts using the U.S. Navy's Arctic Cap Nowcast/Forecast System

NASA Astrophysics Data System (ADS)

Hebert, David A.; Allard, Richard A.; Metzger, E. Joseph; Posey, Pamela G.; Preller, Ruth H.; Wallcraft, Alan J.; Phelps, Michael W.; Smedstad, Ole Martin

2015-12-01

In this study the forecast skill of the U.S. Navy operational Arctic sea ice forecast system, the Arctic Cap Nowcast/Forecast System (ACNFS), is presented for the period February 2014 to June 2015. ACNFS is designed to provide short term, 1-7 day forecasts of Arctic sea ice and ocean conditions. Many quantities are forecast by ACNFS; the most commonly used include ice concentration, ice thickness, ice velocity, sea surface temperature, sea surface salinity, and sea surface velocities. Ice concentration forecast skill is compared to a persistent ice state and historical sea ice climatology. Skill scores are focused on areas where ice concentration changes by ±5% or more, and are therefore limited to primarily the marginal ice zone. We demonstrate that ACNFS forecasts are skilful compared to assuming a persistent ice state, especially beyond 24 h. ACNFS is also shown to be particularly skilful compared to a climatologic state for forecasts up to 102 h. Modeled ice drift velocity is compared to observed buoy data from the International Arctic Buoy Programme. A seasonal bias is shown where ACNFS is slower than IABP velocity in the summer months and faster in the winter months. In February 2015, ACNFS began to assimilate a blended ice concentration derived from Advanced Microwave Scanning Radiometer 2 (AMSR2) and the Interactive Multisensor Snow and Ice Mapping System (IMS). Preliminary results show that assimilating AMSR2 blended with IMS improves the short-term forecast skill and ice edge location compared to the independently derived National Ice Center Ice Edge product.

Historical and Future Black Carbon Deposition on the Three Ice Caps: Ice Core Measurements and Model Simulations from 1850 to 2100

NASA Technical Reports Server (NTRS)

Bauer, Susanne E.; Bausch, Alexandra; Nazarenko, Larissa; Tsigaridis, Kostas; Xu, Baiqing; Edwards. Ross; Bisiaux, Marion; McConnell, Joe

2013-01-01

Ice core measurements in conjunction with climate model simulations are of tremendous value when examining anthropogenic and natural aerosol loads and their role in past and future climates. Refractory black carbon (BC) records from the Arctic, the Antarctic, and the Himalayas are analyzed using three transient climate simulations performed with the Goddard Institute for Space Studies ModelE. Simulations differ in aerosol schemes (bulk aerosols vs. aerosol microphysics) and ocean couplings (fully coupled vs. prescribed ocean). Regional analyses for past (1850-2005) and future (2005-2100) carbonaceous aerosol simulations focus on the Antarctic, Greenland, and the Himalayas. Measurements from locations in the Antarctic show clean conditions with no detectable trend over the past 150 years. Historical atmospheric deposition of BC and sulfur in Greenland shows strong trends and is primarily influenced by emissions from early twentieth century agricultural and domestic practices. Models fail to reproduce observations of a sharp eightfold BC increase in Greenland at the beginning of the twentieth century that could be due to the only threefold increase in the North American emission inventory. BC deposition in Greenland is about 10 times greater than in Antarctica and 10 times less than in Tibet. The Himalayas show the most complicated transport patterns, due to the complex terrain and dynamical regimes of this region. Projections of future climate based on the four CMIP5 Representative Concentration Pathways indicate further dramatic advances of pollution to the Tibetan Plateau along with decreasing BC deposition fluxes in Greenland and the Antarctic.

Intratumoral and Intertumoral Genomic Heterogeneity of Multifocal Localized Prostate Cancer Impacts Molecular Classifications and Genomic Prognosticators

PubMed Central

Wei, Lei; Wang, Jianmin; Lampert, Erika; Schlanger, Simon; DePriest, Adam D.; Hu, Qiang; Gomez, Eduardo Cortes; Murakam, Mitsuko; Glenn, Sean T.; Conroy, Jeffrey; Morrison, Carl; Azabdaftari, Gissou; Mohler, James L.; Liu, Song; Heemers, Hannelore V.

2018-01-01

Background Next-generation sequencing is revealing genomic heterogeneity in localized prostate cancer (CaP). Incomplete sampling of CaP multiclonality has limited the implications for molecular subtyping, stratification, and systemic treatment. Objective To determine the impact of genomic and transcriptomic diversity within and among intraprostatic CaP foci on CaP molecular taxonomy, predictors of progression, and actionable therapeutic targets. Design, setting, and participants Four consecutive patients with clinically localized National Comprehensive Cancer Network intermediate- or high-risk CaP who did not receive neoadjuvant therapy underwent radical prostatectomy at Roswell Park Cancer Institute in June–July 2014. Presurgical information on CaP content and a customized tissue procurement procedure were used to isolate nonmicroscopic and noncontiguous CaP foci in radical prostatectomy specimens. Three cores were obtained from the index lesion and one core from smaller lesions. RNA and DNA were extracted simultaneously from 26 cores with ≥90% CaP content and analyzed using whole-exome sequencing, single-nucleotide polymorphism arrays, and RNA sequencing. Outcome measurements and statistical analysis Somatic mutations, copy number alternations, gene expression, gene fusions, and phylogeny were defined. The impact of genomic alterations on CaP molecular classification, gene sets measured in Oncotype DX, Prolaris, and Decipher assays, and androgen receptor activity among CaP cores was determined. Results and limitations There was considerable variability in genomic alterations among CaP cores, and between RNA- and DNA-based platforms. Heterogeneity was found in molecular grouping of individual CaP foci and the activity of gene sets underlying the assays for risk stratification and androgen receptor activity, and was validated in independent genomic data sets. Determination of the implications for clinical decision-making requires follow-up studies. Conclusions Genomic make-up varies widely among CaP foci, so care should be taken when making treatment decisions based on a single biopsy or index lesions. Patient summary We examined the molecular composition of individual cancers in a patient’s prostate. We found a lot of genetic diversity among these cancers, and concluded that information from a single cancer biopsy is not sufficient to guide treatment decisions. PMID:27451135

Ridges Down South

NASA Image and Video Library

2005-11-04

This image captured by NASA 2001 Mars Odyssey spacecraft shows part of an area just off the margin of the south polar cap. The bright and dark markings are identical to some seen on the cap, telling us that ice is located at the surface.

10Be evidence for the Matuyama-Brunhes geomagnetic reversal in the EPICA Dome C ice core.

PubMed

Raisbeck, G M; Yiou, F; Cattani, O; Jouzel, J

2006-11-02

An ice core drilled at Dome C, Antarctica, is the oldest ice core so far retrieved. On the basis of ice flow modelling and a comparison between the deuterium signal in the ice with climate records from marine sediment cores, the ice at a depth of 3,190 m in the Dome C core is believed to have been deposited around 800,000 years ago, offering a rare opportunity to study climatic and environmental conditions over this time period. However, an independent determination of this age is important because the deuterium profile below a depth of 3,190 m depth does not show the expected correlation with the marine record. Here we present evidence for enhanced 10Be deposition in the ice at 3,160-3,170 m, which we interpret as a result of the low dipole field strength during the Matuyama-Brunhes geomagnetic reversal, which occurred about 780,000 years ago. If correct, this provides a crucial tie point between ice cores, marine cores and a radiometric timescale.

Polar Winds

NASA Image and Video Library

2018-04-05

This VIS image shows 'streamers' of clouds created by katabatic winds at the north polar cap. Katabatic winds are created by cold air sinking at the pole and then speeding along the ice surface towards the edge of the polar cap. When the winds enter troughs the wind regime changes from laminar flow to choatic and clouds of ice particles and/or dust are visible. This wind activity peaks at the start of northern hemisphere summer. Orbit Number: 53942 Latitude: 86.8433 Longitude: 99.3149 Instrument: VIS Captured: 2014-02-10 10:50 https://photojournal.jpl.nasa.gov/catalog/PIA22362

Variations in Surface Texture of the North Polar Residual Cap of Mars

NASA Technical Reports Server (NTRS)

Milkovich, S. M.; Byrne, S.; Russell, P. S.

2011-01-01

The northern polar residual cap (NPRC) of Mars is a water ice deposit with a rough surface made up of pits, knobs, and linear depressions on scales of tens of meters. This roughness manifests as a series of bright mounds and dark hollows in visible images; these bright and dark patches have a characteristic wavelength and orientation. Spectral data indicate that the surface of the NPRC is composed of large-grained (and therefore old) water ice. Due to the presence of this old ice, it is thought that the NPRC is in a current state of net loss of material a result potentially at odds with impact crater statistics, which suggest ongoing deposition over the past 10-20 Kyr.

Drill/borescope System for the Mars Polar Pathfinder

NASA Technical Reports Server (NTRS)

Paige, D. A.; Wood, S. E.; Vasavada, A. R.

1993-01-01

The primary goals of the Mars Polar Pathfinder (MPP) Discovery Mission are to characterize the composition and structure of Mars' north polar ice cap, and to determine whether a climate record may be preserved in layers of ice and dust. The MPP would land as close as possible to the geographic north pole of Mars and use a set of instruments similar to those used by glaciologists to study polar ice caps on Earth: a radar sounder, a drill/borescope system, and a thermal probe. The drill/borescope system will drill approximately 50 cm into the surface and image the sides of the hole at 10 micron resolution for compositional and stratigraphic analysis. Several uncertainties have guided the development of this instrument, and they are discussed.

Lunar and Planetary Science XXXV: Special Session: Mars Climate Change

NASA Technical Reports Server (NTRS)

2004-01-01

The titles in this section include: 1) Mars South Pole CO2 Paleoatmosphere; 2) Do SNC Noble Gas and Deuterium Data Provide Evidence for Large Cometary Impact Between 1300-300 Ma on Mars? 3) Medusae Fossae Formation: Ice-rich Airborne Dust Deposited During Periods of High Obliquity? 4) Ascraeus Mons, Mars: Characterisation and Interpretation of the Fan-shaped Deposit on Its Western Flank; 5) Evidence of Recent Glaciation in Elysium Planitia, Mars; 6) Craters and Other Circular Features in the Northern Circumpolar Area, Mars; 7) Intra-Annual Variations of the Martian Swiss-Cheese Terrain; 8) Drastic Climate Change of Mars Induced by H2O Ice Caps; 9) Modelling the Mass Balance of the North Polar Ice Cap on Mars.

The deglacial history of NW Alexander Island, Antarctica, from surface exposure dating

NASA Astrophysics Data System (ADS)

Johnson, Joanne S.; Everest, Jeremy D.; Leat, Philip T.; Golledge, Nicholas R.; Rood, Dylan H.; Stuart, Finlay M.

2012-03-01

Recent changes along the margins of the Antarctic Peninsula, such as the collapse of the Wilkins Ice Shelf, have highlighted the effects of climatic warming on the Antarctic Peninsula Ice Sheet (APIS). However, such changes must be viewed in a long-term (millennial-scale) context if we are to understand their significance for future stability of the Antarctic ice sheets. To address this, we present nine new cosmogenic 10Be exposure ages from sites on NW Alexander Island and Rothschild Island (adjacent to the Wilkins Ice Shelf) that provide constraints on the timing of thinning of the Alexander Island ice cap since the last glacial maximum. All but one of the 10Be ages are in the range 10.2-21.7 ka, showing a general trend of progressive ice-sheet thinning since at least 22 ka until 10 ka. The data also provide a minimum estimate (490 m) for ice-cap thickness on NW Alexander Island at the last glacial maximum. Cosmogenic 3He ages from a rare occurrence of mantle xenoliths on Rothschild Island yield variable ages up to 46 ka, probably reflecting exhumation by periglacial processes.

MABEL Iceland 2012 Flight Report

NASA Technical Reports Server (NTRS)

Cook, William B.; Brunt, Kelly M.; De Marco, Eugenia L.; Reed, Daniel L.; Neumann, Thomas A.; Markus, Thorsten

2017-01-01

In March and April 2012, NASA conducted an airborne lidar campaign based out of Keflavik, Iceland, in support of Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) algorithm development. The survey targeted the Greenland Ice Sheet, Iceland ice caps, and sea ice in the Arctic Ocean during the winter season. Ultimately, the mission, MABEL Iceland 2012, including checkout and transit flights, conducted 14 science flights, for a total of over 80 flight hours over glaciers, icefields, and sea ice.

Ice cores and SeaRISE: What we do (and don't) know

NASA Technical Reports Server (NTRS)

Alley, Richard B.

1991-01-01

Ice core analyses are needed in SeaRISE to learn what the West Antarctic ice sheet and other marine ice sheets were like in the past, what climate changes led to their present states, and how they behave. The major results of interest to SeaRISE from previous ice core analyses in West Antarctic are that the end of the last ice age caused temperature and accumulation rate increases in inland regions, leading to ice sheet thickening followed by thinning to the present.

Helicopter magnetic and electromagnetic surveys at Mounts Adams, Baker and Rainier, Washington: implications for debris flow hazards and volcano hydrology

USGS Publications Warehouse

Finn, Carol A.; Deszcz-Pan, Maria

2011-01-01

High‐resolution helicopter magnetic and electromagnetic (HEM) data flown over the rugged, ice‐covered Mt. Adams, Mt. Baker and Mt. Rainier volcanoes (Washington), reveal the distribution of alteration, water and ice thickness essential to evaluating volcanic landslide hazards. These data, combined with geological mapping and rock property measurements, indicate the presence of appreciable thicknesses (>500 m) of water‐saturated hydrothermally altered rock west of the modern summit of Mount Rainier in the Sunset Amphitheater region and in the central core of Mount Adams north of the summit. Alteration at Mount Baker is restricted to thinner (<300 m) zones beneath Sherman Crater and the Dorr Fumarole Fields. The EM data identified water‐saturated rocks from the surface to the detection limit (100–200 m) in discreet zones at Mt. Rainier and Mt Adams and over the entire summit region at Mt. Baker. The best estimates for ice thickness are obtained over relatively low resistivity (<800 ohm‐m) ground for the main ice cap on Mt. Adams and over most of the summit of Mt. Baker. The modeled distribution of alteration, pore fluids and partial ice volumes on the volcanoes helps identify likely sources for future alteration‐related debris flows, including the Sunset Amphitheater region at Mt. Rainier, steep cliffs at the western edge of the central altered zone at Mount Adams and eastern flanks of Mt. Baker.

Glacial History of the NE Antarctic Peninsula over centennial to millennial timescales

NASA Astrophysics Data System (ADS)

Davies, B. J.; Glasser, N. F.; Hambrey, M.; Carrivick, J.; Smellie, J.

2010-12-01

A detailed glacier inventory of 232 glaciers was undertaken of the northeast Antarctic Peninsula and James Ross Island for the first time. Glacier inventories provide representative, detailed and natural indications of the impacts of climate change. Documenting the continued response of ice shelf feeder glaciers after the collapse of the Prince Gustav Ice Shelf in 1997 is especially important for predicting future glacier behaviour in this region. James Ross Island has a relatively long history of glacier observations, and offers a unique opportunity to assess the ongoing impacts of a changing climate in a very sensitive part of the global system. This work classified and mapped the glaciers of James Ross Island and the northern Antarctic Peninsula for the first time, documenting change in extent and behaviour in 1988, 2001 and 2009, and characterising glacier response to ice shelf collapse. Glacier altitude, aspect, area, slope and rate of recession were among the indices' measured. James Ross Island is approximately 78% ice-covered, with ice-free terrain exhibiting characteristic permafrost and thermokarst landforms, including rock glaciers and ice-cored moraine. The island is dominated by the cold-based Mount Haddington Ice Cap, which feeds numerous polythermal elongate tidewater valley glaciers. The tidewater glaciers typically form extensive medial, lateral and terminal moraines. Initial inventory results show that ice-shelf feeder tidewater glaciers on the APIS have stabilised since the 1997 collapse of the Prince Gustav Ice Shelf, although recession continues. Of the non-ice-shelf tidewater glaciers, glacier recession has accelerated in the decade since 2001. Land-based valley glacier retreat has accelerated post 2001, in line with continued atmospheric warming. Climate relationships can be determined from altitude-aspect relationships, with glaciers on the drier eastern side of James Ross Island retreating fastest. Glacier mass balances are strongly influenced by glacier hypsometry, aspect, and slope, resulting in asymmetric retreat patterns.

The 1500m South Pole Ice Core: Recovering a 40 Ka Environmental Record

NASA Technical Reports Server (NTRS)

Casey, Kimberly Ann; Neumann, Thomas Allen; Fudge, T. J.; Neumann, T. A.; Steig, E. J.; Cavitte, M. G. P.; Blankenship, D. D.

2014-01-01

Supported by the US National Science Foundation, a new 1500 m, approximately 40 ka old ice core will be recovered from South Pole during the 2014/15 and 2015/16 austral summer seasons using the new US Intermediate Depth Drill. The combination of low temperatures, relatively high accumulation rates and low impurity concentrations at South Pole will yield detailed records of ice chemistry and trace atmospheric gases. The South Pole ice core will provide a climate history record of a unique area of the East Antarctic plateau that is partly influenced by weather systems that cross the West Antarctic ice sheet. The ice at South Pole flows at approximately 10m a(exp-1) and the South Pole ice-core site is a significant distance from an ice divide. Therefore, ice recovered at depth originated progressively farther upstream of the coring site. New ground-penetrating radar collected over the drill site location shows no anthropogenic influence over the past approximately 50 years or upper 15 m. Depth-age scale modeling results show consistent and plausible annual-layer thicknesses and accumulation rate histories, indicating that no significant stratigraphic disturbances exist in the upper 1500m near the ice-core drill site.

IceChrono1: a probabilistic model to compute a common and optimal chronology for several ice cores

NASA Astrophysics Data System (ADS)

Parrenin, Frédéric; Bazin, Lucie; Capron, Emilie; Landais, Amaëlle; Lemieux-Dudon, Bénédicte; Masson-Delmotte, Valérie

2016-04-01

Polar ice cores provide exceptional archives of past environmental conditions. The dating of ice cores and the estimation of the age scale uncertainty are essential to interpret the climate and environmental records that they contain. It is however a complex problem which involves different methods. Here, we present IceChrono1, a new probabilistic model integrating various sources of chronological information to produce a common and optimized chronology for several ice cores, as well as its uncertainty. IceChrono1 is based on the inversion of three quantities: the surface accumulation rate, the Lock-In Depth (LID) of air bubbles and the thinning function. The chronological information integrated into the model are: models of the sedimentation process (accumulation of snow, densification of snow into ice and air trapping, ice flow), ice and air dated horizons, ice and air depth intervals with known durations, Δdepth observations (depth shift between synchronous events recorded in the ice and in the air) and finally air and ice stratigraphic links in between ice cores. The optimization is formulated as a least squares problem, implying that all densities of probabilities are assumed to be Gaussian. It is numerically solved using the Levenberg-Marquardt algorithm and a numerical evaluation of the model's Jacobian. IceChrono follows an approach similar to that of the Datice model which was recently used to produce the AICC2012 chronology for 4 Antarctic ice cores and 1 Greenland ice core. IceChrono1 provides improvements and simplifications with respect to Datice from the mathematical, numerical and programming point of views. The capabilities of IceChrono is demonstrated on a case study similar to the AICC2012 dating experiment. We find results similar to those of Datice, within a few centuries, which is a confirmation of both IceChrono and Datice codes. We also test new functionalities with respect to the original version of Datice: observations as ice intervals with known durations, correlated observations, observations as gas intervals with known durations and observations as mixed ice-air stratigraphic links. IceChrono1 is freely available under the GPL v3 open source license.

Annually-resolved temperature reconstructions of the past 2000 years from Dome-Fuji, East Antarctica

NASA Astrophysics Data System (ADS)

Motizuki, Yuko; Takahashi, Kazuya; Nakai, Yoichi; Motoyama, Hideaki

2016-04-01

We present annually-resolved temperature and SST reconstructions of the past 2000 years based on water (oxygen and deuterium) isotope measurement on a shallow ice core drilled in 2010 at Dome Fuji station, East Antarctica. These time series records will be an essential contribution to the PAGES 2k project from sparse data area in Antarctica. Dome Fuji station is located on a summit of Dronning Maud Land at an altitude of 3810 m a.s.l. (above sea level) (77o19'01'' S, 39o42'12'' E) in East Antarctica. The 10 m depth mean snow temperature at Dome Fuji is -57.3oC1). The inland area around Dome Fuji has been recognized to be especially unique: The snow and ice there contain much stratospheric information. The direct evidence for this comes from tritium contents originated from the nuclear bomb tests in the 1960s; the tritium fallout at the Dome Fuji site is outstandingly high among 16 snow pit samples widely collected over Antarctica2). To date the concerned Dome Fuji ice core, we applied volcanic signature matching to transfer the West Antarctic Ice Sheet (WAIS) Divide ice core chronology constructed by annual layer counting as used in the study by Sigl et al. (2014)3). In our presentation, we confine ourselves to discuss the oscillation periodicity that we observed in the oxygen isotope record in our data: The periods of approximately 10, 20, and 200 years were found. We will present the time series analyses for this in detail, and will discuss the origin of this periodicity. References: 1) Kameda, T., Motoyama, H., Fujita, S., and Takahashi, S.: "Past temporal and spatial variability of surface mass balance at Dome Fuji", East Antarctica, by the stake method from 1995 to 2006, J. Glaciol., 54, 107-116, 2008. 2) Fourre, E., Jean-Baptiste, P., Dapoigny, A., Baumier, D., Petit, J.-R., and Jouzel, J.: "Past and recent tritium levels in Arctic and Antarctic polar caps", Earth Planet. Sc. Lett., 245, 56-64, 2006. 3) Sigl, M., J. McConnell, M. Toohey, M. Curran, S. Das, R. Edwards, E. Isaksson, K. Kawamura, S. Kipfstuhl, K. Kruger, L. Layman, O. Maselli, Y. Motizuki, H. Motoyama, D. Pasteris, M. Severi: "Insights from Antarctica on volcanic forcing during the Common Era", Nature Climate Change, 4, 693-697, 2014.

Rise in central west Greenland surface melt unprecedented over the last three centuries

NASA Astrophysics Data System (ADS)

Trusel, Luke; Das, Sarah; Osman, Matthew; Evans, Matthew; Smith, Ben; McConnell, Joe; Noël, Brice; van den Broeke, Michiel

2017-04-01

Greenland Ice Sheet surface melting has intensified and expanded over the last several decades and is now a leading component of ice sheet mass loss. Here, we constrain the multi-century temporal evolution of surface melt across central west Greenland by quantifying layers of refrozen melt within well-dated firn and ice cores collected in 2014 and 2015, as well as from a core collected in 2004. We find significant agreement among ice core, satellite, and regional climate model melt datasets over recent decades, confirming the fidelity of the ice core melt stratigraphy as a reliable record of past variability in the magnitude of surface melt. We also find a significant correlation between the melt records derived from our new 100-m GC-2015 core (2436 m.a.s.l.) and the older (2004) 150-m D5 core (2472 m.a.s.l.) located 50 km to the southeast. This agreement demonstrates the robustness of the ice core-derived melt histories and the potential for reconstructing regional melt evolution from a single site, despite local variability in melt percolation and refreeze processes. Our array of upper percolation zone cores reveals that although the overall frequency of melt at these sites has not increased, the intensification of melt over the last three decades is unprecedented within at least the last 365 years. Utilizing the regional climate model RACMO 2.3, we show that this melt intensification is a nonlinear response to warming summer air temperatures, thus underscoring the heightened sensitivity of this sector of Greenland to further climate warming. Finally, we examine spatial correlations between the ice core melt records and modeled melt fields across the ice sheet to assess the broader representation of each ice core record. This analysis reveals wide-ranging significant correlations, including to modeled meltwater runoff. As such, our ice core melt records may furthermore offer unique, observationally-constrained insights into past variability in ice sheet mass loss.

Changes of the Bacterial Abundance and Communities in Shallow Ice Cores from Dunde and Muztagata Glaciers, Western China

PubMed Central

Chen, Yong; Li, Xiang-Kai; Si, Jing; Wu, Guang-Jian; Tian, Li-De; Xiang, Shu-Rong

2016-01-01

In this study, six bacterial community structures were analyzed from the Dunde ice core (9.5-m-long) using 16S rRNA gene cloning library technology. Compared to the Muztagata mountain ice core (37-m-long), the Dunde ice core has different dominant community structures, with five genus-related groups Blastococcus sp./Propionibacterium, Cryobacterium-related., Flavobacterium sp., Pedobacter sp., and Polaromas sp. that are frequently found in the six tested ice layers from 1990 to 2000. Live and total microbial density patterns were examined and related to the dynamics of physical-chemical parameters, mineral particle concentrations, and stable isotopic ratios in the precipitations collected from both Muztagata and Dunde ice cores. The Muztagata ice core revealed seasonal response patterns for both live and total cell density, with high cell density occurring in the warming spring and summer months indicated by the proxy value of the stable isotopic ratios. Seasonal analysis of live cell density for the Dunde ice core was not successful due to the limitations of sampling resolution. Both ice cores showed that the cell density peaks were frequently associated with high concentrations of particles. A comparison of microbial communities in the Dunde and Muztagata glaciers showed that similar taxonomic members exist in the related ice cores, but the composition of the prevalent genus-related groups is largely different between the two geographically different glaciers. This indicates that the micro-biogeography associated with geographic differences was mainly influenced by a few dominant taxonomic groups. PMID:27847503

An Optical Dye Method for Continuous Determination of Acidity in Ice Cores.

PubMed

Kjær, Helle Astrid; Vallelonga, Paul; Svensson, Anders; Elleskov L Kristensen, Magnus; Tibuleac, Catalin; Winstrup, Mai; Kipfstuhl, Sepp

2016-10-04

The pH of polar ice is important for the stability and mobility of impurities in ice cores and can be strongly influenced by volcanic eruptions or anthropogenic emissions. We present a simple optical method for continuous determination of acidity in ice cores based on spectroscopically determined color changes of two common pH-indicator dyes, bromophenol blue, and chlorophenol red. The sealed-system method described here is not equilibrated with CO 2 , making it simpler than existing methods for pH determination in ice cores and offering a 10-90% peak response time of 45 s and a combined uncertainty of 9%. The method is applied to Holocene ice core sections from Greenland and Antarctica and compared to standard techniques such as electrical conductivity measurement (ECM) conducted on the solid ice, and electrolytic meltwater conductivity, EMWC. Acidity measured in the Greenland NGRIP ice core shows good agreement with acidity calculated from ion chromatography. Conductivity and dye-based acidity H dye + are found to be highly correlated in the Greenland NEGIS firn core (75.38° N, 35.56° W), with all signals greater than 3σ variability coinciding with either volcanic eruptions or possible wild fire activity. In contrast, the Antarctic Roosevelt Island ice core (79.36° S, 161.71° W) features an anticorrelation between conductivity and H dye + , likely due to strong influence of marine salts.

Sea ice and pollution-modulated changes in Greenland ice core methanesulfonate and bromine

NASA Astrophysics Data System (ADS)

Maselli, Olivia J.; Chellman, Nathan J.; Grieman, Mackenzie; Layman, Lawrence; McConnell, Joseph R.; Pasteris, Daniel; Rhodes, Rachael H.; Saltzman, Eric; Sigl, Michael

2017-01-01

Reconstruction of past changes in Arctic sea ice extent may be critical for understanding its future evolution. Methanesulfonate (MSA) and bromine concentrations preserved in ice cores have both been proposed as indicators of past sea ice conditions. In this study, two ice cores from central and north-eastern Greenland were analysed at sub-annual resolution for MSA (CH3SO3H) and bromine, covering the time period 1750-2010. We examine correlations between ice core MSA and the HadISST1 ICE sea ice dataset and consult back trajectories to infer the likely source regions. A strong correlation between the low-frequency MSA and bromine records during pre-industrial times indicates that both chemical species are likely linked to processes occurring on or near sea ice in the same source regions. The positive correlation between ice core MSA and bromine persists until the mid-20th century, when the acidity of Greenland ice begins to increase markedly due to increased fossil fuel emissions. After that time, MSA levels decrease as a result of declining sea ice extent but bromine levels increase. We consider several possible explanations and ultimately suggest that increased acidity, specifically nitric acid, of snow on sea ice stimulates the release of reactive Br from sea ice, resulting in increased transport and deposition on the Greenland ice sheet.

Nature and Stability of the Martian Seasonal Water Cycle

NASA Astrophysics Data System (ADS)

Richardson, M. I.; Wilson, R. J.

2001-12-01

Which components control the contemporary water cycle and what is the nature of the control mechanisms? These questions are at the heart of understanding how the Martian exchangeable water budget adjusts to perturbations and changes in the climate system. Analysis of a water cycle model embedded in the GFDL Mars GCM provides a paradigm for the water cycle as a feedback system, providing information on the important control points and response times. Much information on this system derives from monitoring the evolution towards steady state--one that resembles the observed water vapour and ice cloud distributions. The most important exchange balance in the system is that between the northern polar atmosphere and the rest of the planet. As the major net source for water, the northern residual water ice cap is active during summer, in the window of time between the sublimation and recondensation of the seasonal CO2 cap. At this time, water is exported from the northern polar atmosphere at a rate determined by the mixing capacity of the atmosphere and the amount of water held in the polar atmosphere. The latter is determined by the cap surface temperature. During the remainder of the year, water is returned to the pole. This return flux is determined by the atmospheric mixing capacity and the amount of water vapour held in the tropical and winter extratropical atmosphere. Steady-state is achieved when these fluxes balance. For a given climate state (and a roughly repeatable annual cycle of mixing), the outflux and influx of polar water are controlled by separate variables. Holding the cap temperature constant, the outflux will remain constant. Any perturbation to the global water budget will result in a change in the return flux that tends to oppose the sense of the perturbation--the perturbation will be damped. In the same way, a change in cap temperature (e.g. associated with a change in albedo) will result in changed water outflow. Again, this will tend to change the non-polar water vapour budget and hence the polar water influx so as to develop a new steady-state. It is important to note that only in this case is the steady-state global humidity changed: a given cap temperature and seasonal cycle of mixing capacity specifies a bulk steady-state atmospheric humidity. In all cases, the regolith acts as a damper on the system and adjusts to the global water distribution dictated ultimately by the northern cap. The model also suggests fast adjustment times, on order decades. A number of factors can affect atmospheric mixing capacity. As climate forcing factors change (associated with obliquity or greenhouse gas loading) the mixing capacity will change--an area for future study. The current mixing capacity of the atmosphere is also different from one that would obtain without atmospheric water condensation and sedimentation. Model clouds play important roles in returning water to the residual ice cap in northern summer, and significantly altering interhemispheric transport from that which would occur without clouds. As with previous studies, the southern polar cap acts as a permanent sink for water. The model and resulting paradigm for the water cycle can be used in very preliminary studies of past climate states. Forcing the model with an obliquity of 45 deg., the seasonal water ice caps become significantly more extended, reaching into the summer hemisphere. In fact, the seasonal caps "overlap" in the northern tropics, generating a year-round surface ice belt. Much work remains to be done in understanding water ice transport and exchange processes before models of paleoclimate can be of widespread utility--of which analysis of data from MGS and future missions will be key.

The Navy's First Seasonal Ice Forecasts using the Navy's Arctic Cap Nowcast/Forecast System

NASA Astrophysics Data System (ADS)

Preller, Ruth

2013-04-01

As conditions in the Arctic continue to change, the Naval Research Laboratory (NRL) has developed an interest in longer-term seasonal ice extent forecasts. The Arctic Cap Nowcast/Forecast System (ACNFS), developed by the Oceanography Division of NRL, was run in forward model mode, without assimilation, to estimate the minimum sea ice extent for September 2012. The model was initialized with varying assimilative ACNFS analysis fields (June 1, July 1, August 1 and September 1, 2012) and run forward for nine simulations using the archived Navy Operational Global Atmospheric Prediction System (NOGAPS) atmospheric forcing fields from 2003-2011. The mean ice extent in September, averaged across all ensemble members was the projected summer ice extent. These results were submitted to the Study of Environmental Arctic Change (SEARCH) Sea Ice Outlook project (http://www.arcus.org/search/seaiceoutlook). The ACNFS is a ~3.5 km coupled ice-ocean model that produces 5 day forecasts of the Arctic sea ice state in all ice covered areas in the northern hemisphere (poleward of 40° N). The ocean component is the HYbrid Coordinate Ocean Model (HYCOM) and is coupled to the Los Alamos National Laboratory Community Ice CodE (CICE) via the Earth System Modeling Framework (ESMF). The ocean and ice models are run in an assimilative cycle with the Navy's Coupled Ocean Data Assimilation (NCODA) system. Currently the ACNFS is being transitioned to operations at the Naval Oceanographic Office.

Quasi-periodic climatic changes on Mars and earth

NASA Technical Reports Server (NTRS)

Cutts, J. A.; Pollack, J. B.; Toon, O. B.; Howard, A. D.

1981-01-01

Evidence of climatic changes on Mars and the earth due to geologic and astronomical variations is discussed. Finely striped ice-free bands in the Martian polar caps have been taken to indicate that long term variations in the orbit and axial tilt of Mars have precipitated these features at the rate of a mm/yr. Photogrammetric and photometric methods have contributed to measurements of the composition and depth of the Martian caps (14-46 m), and observations of higher solar energy absorption in the northern ice cap implies greater dust deposition in that region than on the south cap; however, the transport mechanisms are not well understood. Comparisons of earth and Martian climatic variations data are made, noting a lack of information on the age intervals of marine and nonmarine sediments on the earth. The possibilities of using quantitative data other than layer thickness to constrain climate models are discussed, and the slope or albedo of layers, or the spacing of polar undulations are suggested.

Albedo of the south pole on Mars determined by topographic forcing of atmosphere dynamics

USGS Publications Warehouse

Colaprete, A.; Barnes, J.R.; Haberle, R.M.; Hollingsworth, J.L.; Kieffer, H.H.; Titus, T.N.

2005-01-01

The nature of the martian south polar cap has remained enigmatic since the first spacecraft observations. In particular, the presence of a perennial carbon dioxide ice cap, the formation of a vast area of black 'slab ice' known as the Cryptic region and the asymmetric springtime retreat of the cap have eluded explanation. Here we present observations and climate modelling that indicate the south pole of Mars is characterized by two distinct regional climates that are the result of dynamical forcing by the largest southern impact basins, Argyre and Hellas. The style of surface frost deposition is controlled by these regional climates. In the cold and stormy conditions that exist poleward of 60?? S and extend 180?? in longitude west from the Mountains of Mitchel (???30?? W), surface frost accumulation is dominated by precipitation. In the opposite hemisphere, the polar atmosphere is relatively warm and clear and frost accumulation is dominated by direct vapour deposition. It is the differences in these deposition styles that determine the cap albedo.

Water Cycling in the North Polar Region of Mars

NASA Technical Reports Server (NTRS)

Tamppari, L. K.; Smith, M. D.; Bass, D. S.

2003-01-01

To date, there has been no comprehensive study to understand the partitioning of water into vapor and ice clouds, and the associated effects of dust and surface temperature in the north polar region. Ascertaining the degree to which water is transported out of the cap region versus within the cap region will give much needed insight into the overall story of water cycling on a seasonal basis. In particular, understanding the mechanism for the polar cap surface albedo changes would go along way in comprehending the sources and sinks of water in the northern polar region. We approach this problem by examining Thermal Emission Spectrometer (TES) atmospheric and surface data acquired in the northern summer season and comparing it to Viking data when possible. Because the TES instrument spans the absorption bands of water vapor, water ice, dust, and measures surface temperature, all three aerosols and surface temperature can be retrieved simultaneously. This presentation will show our latest results on the water vapor, water-ice clouds seasonal and spatial distributions, as well as surface temperatures and dust distribution which may lend insight into where the water is going.

Mountain Glaciers and Ice Caps

USGS Publications Warehouse

Ananichheva, Maria; Arendt, Anthony; Hagen, Jon-Ove; Hock, Regine; Josberger, Edward G.; Moore, R. Dan; Pfeffer, William Tad; Wolken, Gabriel J.

2011-01-01

Projections of future rates of mass loss from mountain glaciers and ice caps in the Arctic focus primarily on projections of changes in the surface mass balance. Current models are not yet capable of making realistic forecasts of changes in losses by calving. Surface mass balance models are forced with downscaled output from climate models driven by forcing scenarios that make assumptions about the future rate of growth of atmospheric greenhouse gas concentrations. Thus, mass loss projections vary considerably, depending on the forcing scenario used and the climate model from which climate projections are derived. A new study in which a surface mass balance model is driven by output from ten general circulation models (GCMs) forced by the IPCC (Intergovernmental Panel on Climate Change) A1B emissions scenario yields estimates of total mass loss of between 51 and 136 mm sea-level equivalent (SLE) (or 13% to 36% of current glacier volume) by 2100. This implies that there will still be substantial glacier mass in the Arctic in 2100 and that Arctic mountain glaciers and ice caps will continue to influence global sea-level change well into the 22nd century.

PolarWinds I & II

Atmospheric Science Data Center

2018-04-20

... (Organized Large Eddies), and near surface winds over open water, transitional ice zones and the Greenland Ice Cap. Polar Winds I was ... total, twenty-four individual missions with over 80 hours of research flights were flown in the Arctic region near Greenland and Iceland ...

TES premapping data: Slab ice and snow flurries in the Martian north polar night

USGS Publications Warehouse

Titus, T.N.; Kieffer, H.H.; Mullins, K.F.; Christensen, P.R.

2001-01-01

In the 1970s, Mariner and Viking spacecraft observations of the north polar region of Mars revealed polar brightness temperatures that were significantly below the expected kinetic temperatures for CO2 sublimation. For the past few decades, the scientific community has speculated as to the nature of these Martian polar cold spots. Thermal Emission Spectrometer (TES) thermal spectral data have shown these cold spots to result largely from fine-grained, CO2 and have constrained most of these cold spots to the surface (or near-surface). Cold spot formation is strongly dependent on topography, forming preferentially near craters and on polar slopes. TES data, combined with Mars Orbiter Laser Altimeter (MOLA) cloud data, suggest atmospheric condensates form a small fraction of the observed cold spots. TES observations of spectra close to a blackbody indicate that another major component of the polar cap is slab CO2 ice; these spectrally bland regions commonly have a low albedo. The cause is uncertain but may result from most of the light being reflected toward the specular direction, from the slab ice being intrinsically dark, or from it being transparent. Regions of the cap where the difference between the brightness temperatures at 18 ??m (T18) and 25 ??m (T25) is less than 5?? are taken to indicate deposits of slab ice. Slab ice is the dominant component of the polar cap at latitudes outside of the polar night. Copyright 2001 by the American Geophysical Union.

Modeling ground thermal regime of an ancient buried ice body in Beacon Valley, Antarctica using a 1-D heat equation with latent heat effect

NASA Astrophysics Data System (ADS)

Liu, L.; Sletten, R. S.; Hallet, B.; Waddington, E. D.; Wood, S. E.

2013-12-01

An ancient massive ice body buried under several decimeters of debris in Beacon Valley, Antarctica is believed to be over one million years old, making it older than any known glacier or ice cap. It is fundamentally important as a reservoir of water, proxy for climatic information, and an expression of the periglacial landscape. It is also one of Earth's closest analog for widespread, near-surface ice found in Martian soils and ice-cored landforms. We are interested in understanding controls on how long this ice may persist since our physical model of sublimation suggests it should not be stable. In these models, the soil temperatures and the gradient are important because it determines the direction and magnitude of the vapor flux, and thus sublimation rates. To better understand the heat transfer processes and constrain the rates of processes governing ground ice stability, a model of the thermal behavior of the permafrost is applied to Beacon Valley, Antarctica. It calculates soil temperatures based on a 1-D thermal diffusion equation using a fully implicit finite volume method (FVM). This model is constrained by soil physical properties and boundary conditions of in-situ ground surface temperature measurements (with an average of -23.6oC, a maximum of 20.5oC and a minimum of -54.3oC) and ice-core temperature record at ~30 m. Model results are compared to in-situ temperature measurements at depths of 0.10 m, 0.20 m, 0.30 m, and 0.45 m to assess the model's ability to reproduce the temperature profile for given thermal properties of the debris cover and ice. The model's sensitivity to the thermal diffusivity of the permafrost and the overlaying debris is also examined. Furthermore, we incorporate the role of ice condensation/sublimation which is calculated using our vapor diffusion model in the 1-D thermal diffusion model to assess potential latent heat effects that in turn affect ground ice sublimation rates. In general, the model simulates the ground thermal regime well. Detailed temperature comparison suggests that the 1-D thermal diffusion model results closely approximate the measured temperature at all depths with the average square root of the mean squared error (SRMSE) of 0.15oC; a linear correlation between modeled and measured temperatures yields an average R2 value of 0.9997. Prominent seasonal temperature variations diminish with depth, and it equilibrates to mean annual temperature at about 21.5 m depth. The amount of heat generated/consumed by ice condensation/sublimation is insufficient to significantly impact the thermal regime.

Effects of Atmospheric Dust on Residual South Polar Cap Stability

NASA Technical Reports Server (NTRS)

Bonrv, B. P.; Bjorkman, J. E.; Hansen, G. B.; James, P. B.; Wolff, M. J.

2005-01-01

The Martian polar caps have been studied from the time of Herschel. Neither polar cap normally disappears in summer. The Residual North Polar Cap (portion that remains through summer) is composed of a mixture of water ice and dust, and its interannual stability is due to its low sublimation rate at the summer temperatures in the North Polar Region. The Residual South Polar Cap (RSPC) is more enigmatic, surviving the relatively hot perihelic summer season despite being composed of much more volatile CO2. It is able to do so because of its unusually high albedo, which is larger than that of other bright regions in the seasonal cap (e.g. Mountains of Mitchel). The proximity of the albedo of the RSPC to the critical albedo for stability raises the question of whether the RSPC exists in every Martian year. The ground based record is somewhat ambivalent. Douglass and Lowell reported that RSPC suddenly vanished at Ls=297deg in 1894 and did not reappear until Ls=0deg [1], and Kuiper reported that it disappeared in 1956 [2]; but both observations were questioned by contemporaries, who tended to attribute them to obscuring dust. Barker [3] reported a large amount of water vapor over the south polar cap in 1969 that could be attributed to exposure of near surface water ice during partial removal of the CO2 in the RSPC in 1969.

Mars Surface Diversity as Revealed by the OMEGA/Mars Express Observations

NASA Astrophysics Data System (ADS)

Bibring, Jean-Pierre; Langevin, Yves; Gendrin, Aline; Gondet, Brigitte; Poulet, François; Berthé, Michel; Soufflot, Alain; Arvidson, Ray; Mangold, Nicolas; Mustard, John; Drossart, P.; OMEGA Team; Erard, Stéphane; Forni, Olivier; Combes, Michel; Encrenaz, Thérèse; Fouchet, Thierry; Merchiorri, Riccardo; Belluci, GianCarlo; Altieri, Francesca; Formisano, Vittorio; Bonello, Guillaume; Capaccioni, Fabricio; Cerroni, Pricilla; Coradini, Angioletta; Fonti, Sergio; Kottsov, Volodia; Ignatiev, Nikolai; Moroz, Vassili; Titov, Dimitri; Zasova, Ludmilla; Mangold, Micholas; Pinet, Patrick; Douté, Sylvain; Schmitt, Bernard; Sotin, Christophe; Hauber, Ernst; Hoffmann, Harald; Jaumann, Ralf; Keller, Uwe; Duxbury, Tom; Forget, François

2005-03-01

The Observatoire pour la Minéralogie, l'Eau, les Glaces, et l'Activité (OMEGA) investigation, on board the European Space Agency Mars Express mission, is mapping the surface composition of Mars at a 0.3- to 5-kilometer resolution by means of visible-near-infrared hyperspectral reflectance imagery. The data acquired during the first 9 months of the mission already reveal a diverse and complex surface mineralogy, offering key insights into the evolution of Mars. OMEGA has identified and mapped mafic iron-bearing silicates of both the northern and southern crust, localized concentrations of hydrated phyllosilicates and sulfates but no carbonates, and ices and frosts with a water-ice composition of the north polar perennial cap, as for the south cap, covered by a thin carbon dioxide-ice veneer.

Establishing a Reliable Depth-Age Relationship for the Denali Ice Core

NASA Astrophysics Data System (ADS)

Wake, C. P.; Osterberg, E. C.; Winski, D.; Ferris, D.; Kreutz, K. J.; Introne, D.; Dalton, M.

2015-12-01

Reliable climate reconstruction from ice core records requires the development of a reliable depth-age relationship. We have established a sub-annual resolution depth-age relationship for the upper 198 meters of a 208 m ice core recovered in 2013 from Mt. Hunter (3,900 m asl), Denali National Park, central Alaska. The dating of the ice core was accomplished via annual layer counting of glaciochemical time-series combined with identification of reference horizons from volcanic eruptions and atmospheric nuclear weapons testing. Using the continuous ice core melter system at Dartmouth College, sub-seasonal samples have been collected and analyzed for major ions, liquid conductivity, particle size and concentration, and stable isotope ratios. Annual signals are apparent in several of the chemical species measured in the ice core samples. Calcium and magnesium peak in the spring, ammonium peaks in the summer, methanesulfonic acid (MSA) peaks in the autumn, and stable isotopes display a strong seasonal cycle with the most depleted values occurring during the winter. Thin ice layers representing infrequent summertime melt were also used to identify summer layers in the core. Analysis of approximately one meter sections of the core via nondestructive gamma spectrometry over depths from 84 to 124 m identified a strong radioactive cesium-137 peak at 89 m which corresponds to the 1963 layer deposited during extensive atmospheric nuclear weapons testing. Peaks in the sulfate and chloride record have been used for the preliminary identification of volcanic signals preserved in the ice core, including ten events since 1883. We are confident that the combination of robust annual layers combined with reference horizons provides a timescale for the 20th century that has an error of less than 0.5 years, making calibrations between ice core records and the instrumental climate data particularly robust. Initial annual layer counting through the entire 198 m suggests the Denali Ice Core record will span the past 1000 years.

Bipolar volcanic events in ice cores and the Toba eruption at 74 ka BP (Invited)

NASA Astrophysics Data System (ADS)

Svensson, A.

2013-12-01

Acidity spikes in Greenland and Antarctic ice cores are applied as tracers of past volcanic activity. Besides providing information on the timing and magnitude of past eruptions, the acidity spikes are also widely used for synchronization of ice cores. All of the deep Greenland ice cores are thus synchronized throughout the last glacial cycle based on volcanic markers. Volcanic matching of ice cores from the two Hemispheres is much more challenging but it is feasible in periods of favourable conditions. Over the last two millennia, where ice cores are precisely dated, some 50 bipolar volcanic events have thus been identified. In order for an eruption to express a bipolar fingerprint it generally needs to be a low latitude eruption with stratospheric injection. Sometimes tephra is associated with the ice-core acidity spikes, but most often there is no tephra present in the ice. As yet, an unknown eruption occurring in 1259 AD is the only event reported to have deposited tephra in both Greenland and Antarctica. During the last glacial period bipolar volcanic matching is very challenging and very little work has been done, but recent high-resolution ice core records have the potential to provide bipolar ice core matching for some periods. Recently, Greenland and Antarctic ice cores have been linked by acidity spikes in the time window of the most recent eruption (the YTT eruption) of the Indonesian Toba volcano that is situated close to equator in Sumatra. Ash from this Toba event is widespread over large areas in Asia and has been identified as far west as Africa, but no corresponding tephra has been found in polar ice cores despite several attempts. The age of the YTT eruption is well constrained by recent Ar-Ar dating to have occurred some 74 ka ago close to the Marine Isotope Stage 4/5 boundary and close to the onset of the cold Greenland Stadial 20 and the corresponding mild Antarctic Isotopic Maxima 19 and 20. Surprisingly, no single outstanding acidity spike can be associated with the YTT Toba eruption in Greenland or Antarctica. Instead, several large bipolar ice cores acidity spikes are occurring within a couple of centuries at the time of the YTT eruption. To complicate matters, the intensity of those acidity spikes varies greatly from ice core to ice core. At this point, it is therefore impossible to relate the Toba eruption to a single event in the ice cores. Probably there have been several large low-latitude eruptions occurring close to the time of the YTT or the Toba volcano itself had multiple large eruptions within centuries. Bipolar volcanic matching allows for an estimation of the climatic impact of eruptions on a global scale. In the case of Toba, there must have been a global cooling following the enormous eruption, but unfortunately at this depth the resolution of the ice core temperature proxies does not allow for an identification of short term events (<100 yr). A significant warming event in Antarctica following the period associated with the YTT shows, however, that Toba did not initiate a long-term global cooling (>100 yr). At the time of YTT it appears that the inter-hemispheric climate variability is governed by the bipolar seesaw pattern that is active throughout most of the last glacial period. Still, it is intriguing that Toba occurs right at the time when Greenland and much of the northern Hemisphere enters its most extreme cold stadial of the last glacial period.

Initial Continuous Chemistry Results From The Roosevelt Island Ice Core (RICE)

NASA Astrophysics Data System (ADS)

Kjær, H. A.; Vallelonga, P. T.; Simonsen, M. F.; Neff, P. D.; Bertler, N. A. N.; Svensson, A.; Dahl-Jensen, D.

2014-12-01

The Roosevelt Island ice core (79.36° S, -161.71° W) was drilled in 2011-13 at the top of the Roosevelt Island ice dome, a location surrounded by the Ross ice shelf. The RICE ice core provides a unique opportunity to look into the past evolution of the West Antarctic Ice sheet. Further the site has high accumulation; 0.26 m of ice equivalent is deposited annually allowing annual layer determination for many chemical parameters. The RICE core was drilled to bedrock and has a total length of 763 metres. Preliminary results derived from water isotopes suggest that the oldest ice reaches back to the Eemian, with the last glacial being compressed in the bottom 60 metres. We present preliminary results from the RICE ice core including continuous measurements of acidity using an optical dye method, insoluble dust particles, conductivity and calcium. The core was analyzed at the New Zealand National Ice Core Research Facility at GNS Science in Wellington. The analytical set up used to determine climate proxies in the ice core was a modified version of the Copenhagen CFA system (Bigler et al., 2011). Key volcanic layers have been matched to those from the WAIS record (Sigl et al., 2013). A significant anti-correlation between acidity and calcium was seen in the Holocene part of the record. Due to the proximity to the ocean a large fraction of the calcium originates from sea salt and is in phase with total conductivity and sodium. In combination with the insoluble dust record, calcium has been apportioned into ocean-related and dust-related sources. Variability over the Holocene is presented and attributed to changing inputs of marine and dust aerosols.

Self-sustaining Mars colonies utilizing the North Polar Cap and the Martian atmosphere.

PubMed

Powell, J; Maise, G; Paniagua, J

2001-01-01

A revolutionary new concept for the early establishment of robust, self-sustaining Martian colonies is described. The colonies would be located on the North Polar Cap of Mars and utilize readily available water ice and the CO2 Martian atmosphere as raw materials to produce all of the propellants, fuel, air, water, plastics, food, and other supplies needed by the colony. The colonists would live in thermally insulated large, comfortable habitats under the ice surface, fully shielded from cosmic rays. The habitats and supplies would be produced by a compact, lightweight (~4 metric tons) nuclear powered robotic unit termed ALPH (Atomic Liberation of Propellant and Habitat), which would land 2 years before the colonists arrived. Using a compact, lightweight 5 MW (th) nuclear reactor/steam turbine (1 MW(e)) power source and small process units (e.g., H2O electrolyzer, H2 and O2 liquefiers, methanator, plastic polymerizer, food producer, etc.) ALPH would stockpile many hundreds of tons of supplies in melt cavities under the ice, plus insulated habitats, to be in place and ready for use when the colonists landed. With the stockpiled supplies, the colonists would construct and operate rovers and flyers to explore the surface of Mars. ALPH greatly reduces the amount of Earth supplied material needed and enables large permanent colonies on Mars. It also greatly reduces human and mission risks and vastly increases the capability not only for exploration of the surrounding Martian surface, but also the ice cap itself. The North Polar Cap is at the center of the vast ancient ocean that covered much of the Martian Northern Hemisphere. Small, nuclear heated robotic probes would travel deep (1 km or more) inside the ice cap, collecting data on its internal structure, the composition and properties of the ancient Martian atmosphere, and possible evidence of ancient life forms (microfossils, traces of DNA, etc.) that were deposited either by wind or as remnants of the ancient ocean. Details of the ALPH system, which is based on existing technology, are presented. ALPH units could be developed and demonstrated on Earth ice sheets within a few years. An Earth-Mars space transport architecture is described, in which Mars produced propellant and supplies for return journeys to Earth would be lifted with relatively low DeltaV to Mars orbit, and from there transported back to Earth orbit, enabling faster and lower cost trips from Earth to Mars. The exploration capability and quality of life in a mature Martian colony of 500 persons located on the North Polar Cap is outlined. c2001 International Astronautical Federation. Published by Elsevier Science Ltd.

Discovery of a hypersaline subglacial lake complex beneath Devon Ice Cap, Canadian Arctic

PubMed Central

Blankenship, Donald D.; Schroeder, Dustin M.; Dowdeswell, Julian A.

2018-01-01

Subglacial lakes are unique environments that, despite the extreme dark and cold conditions, have been shown to host microbial life. Many subglacial lakes have been discovered beneath the ice sheets of Antarctica and Greenland, but no spatially isolated water body has been documented as hypersaline. We use radio-echo sounding measurements to identify two subglacial lakes situated in bedrock troughs near the ice divide of Devon Ice Cap, Canadian Arctic. Modeled basal ice temperatures in the lake area are no higher than −10.5°C, suggesting that these lakes consist of hypersaline water. This implication of hypersalinity is in agreement with the surrounding geology, which indicates that the subglacial lakes are situated within an evaporite-rich sediment unit containing a bedded salt sequence, which likely act as the solute source for the brine. Our results reveal the first evidence for subglacial lakes in the Canadian Arctic and the first hypersaline subglacial lakes reported to date. We conclude that these previously unknown hypersaline subglacial lakes may represent significant and largely isolated microbial habitats, and are compelling analogs for potential ice-covered brine lakes and lenses on planetary bodies across the solar system. PMID:29651462

Response of faults to climate-driven changes in ice and water volumes on Earth's surface.

PubMed

Hampel, Andrea; Hetzel, Ralf; Maniatis, Georgios

2010-05-28

Numerical models including one or more faults in a rheologically stratified lithosphere show that climate-induced variations in ice and water volumes on Earth's surface considerably affect the slip evolution of both thrust and normal faults. In general, the slip rate and hence the seismicity of a fault decreases during loading and increases during unloading. Here, we present several case studies to show that a postglacial slip rate increase occurred on faults worldwide in regions where ice caps and lakes decayed at the end of the last glaciation. Of note is that the postglacial amplification of seismicity was not restricted to the areas beneath the large Laurentide and Fennoscandian ice sheets but also occurred in regions affected by smaller ice caps or lakes, e.g. the Basin-and-Range Province. Our results do not only have important consequences for the interpretation of palaeoseismological records from faults in these regions but also for the evaluation of the future seismicity in regions currently affected by deglaciation like Greenland and Antarctica: shrinkage of the modern ice sheets owing to global warming may ultimately lead to an increase in earthquake frequency in these regions.

Visual-Stratigraphic Dating of the GISP2 Ice Core: Basis, Reproducibility, and Application

NASA Technical Reports Server (NTRS)

Alley, R. B.; Shuman, C. A.; Meese, D. A.; Gow, A. J.; Taylor, K. C.; Cuffey, K. M.; Fitzpatrick, J. J.; Grootes, P. M.; Zielinski, G. A.; Ram, M.;

Visual-stratigraphic dating of the GISP2 ice core: Basis, reproducibility, and application

NASA Astrophysics Data System (ADS)

Alley, R. B.; Shuman, C. A.; Meese, D. A.; Gow, A. J.; Taylor, K. C.; Cuffey, K. M.; Fitzpatrick, J. J.; Grootes, P. M.; Zielinski, G. A.; Ram, M.; Spinelli, G.; Elder, B.

1997-11-01

Annual layers are visible in the Greenland Ice Sheet Project 2 ice core from central Greenland, allowing rapid dating of the core. Changes in bubble and grain structure caused by near-surface, primarily summertime formation of hoar complexes provide the main visible annual marker in the Holocene, and changes in "cloudiness" of the ice correlated with dustiness mark Wisconsinan annual cycles; both markers are evident and have been intercalibrated in early Holocene ice. Layer counts are reproducible between different workers and for one worker at different times, with 1% error over century-length times in the Holocene. Reproducibility is typically 5% in Wisconsinan ice-age ice and decreases with increasing age and depth. Cumulative ages from visible stratigraphy are not significantly different from independent ages of prominent events for ice older than the historical record and younger than approximately 50,000 years. Visible observations are not greatly degraded by "brittle ice" or many other core-quality problems, allowing construction of long, consistently sampled time series. High accuracy requires careful study of the core by dedicated observers.

The design and performance of IceCube DeepCore

NASA Astrophysics Data System (ADS)

Abbasi, R.; Abdou, Y.; Abu-Zayyad, T.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Allen, M. M.; Altmann, D.; Andeen, K.; Auffenberg, J.; Bai, X.; Baker, M.; Barwick, S. W.; Bay, R.; Bazo Alba, J. L.; Beattie, K.; Beatty, J. J.; Bechet, S.; Becker, J. K.; Becker, K.-H.; Benabderrahmane, M. L.; BenZvi, S.; Berdermann, J.; Berghaus, P.; Berley, D.; Bernardini, E.; Bertrand, D.; Besson, D. Z.; Bindig, D.; Bissok, M.; Blaufuss, E.; Blumenthal, J.; Boersma, D. J.; Bohm, C.; Bose, D.; Böser, S.; Botner, O.; Brown, A. M.; Buitink, S.; Caballero-Mora, K. S.; Carson, M.; Chirkin, D.; Christy, B.; Clevermann, F.; Cohen, S.; Colnard, C.; Cowen, D. F.; Cruz Silva, A. H.; D'Agostino, M. V.; Danninger, M.; Daughhetee, J.; Davis, J. C.; De Clercq, C.; Degner, T.; Demirörs, L.; Descamps, F.; Desiati, P.; de Vries-Uiterweerd, G.; DeYoung, T.; Díaz-Vélez, J. C.; Dierckxsens, M.; Dreyer, J.; Dumm, J. P.; Dunkman, M.; Eisch, J.; Ellsworth, R. W.; Engdegård, O.; Euler, S.; Evenson, P. A.; Fadiran, O.; Fazely, A. R.; Fedynitch, A.; Feintzeig, J.; Feusels, T.; Filimonov, K.; Finley, C.; Fischer-Wasels, T.; Fox, B. D.; Franckowiak, A.; Franke, R.; Gaisser, T. K.; Gallagher, J.; Gerhardt, L.; Gladstone, L.; Glüsenkamp, T.; Goldschmidt, A.; Goodman, J. A.; Góra, D.; Grant, D.; Griesel, T.; Groß, A.; Grullon, S.; Gurtner, M.; Ha, C.; Haj Ismail, A.; Hallgren, A.; Halzen, F.; Han, K.; Hanson, K.; Heinen, D.; Helbing, K.; Hellauer, R.; Hickford, S.; Hill, G. C.; Hoffman, K. D.; Hoffmann, B.; Homeier, A.; Hoshina, K.; Huelsnitz, W.; Hülß, J.-P.; Hulth, P. O.; Hultqvist, K.; Hussain, S.; Ishihara, A.; Jacobi, E.; Jacobsen, J.; Japaridze, G. S.; Johansson, H.; Kampert, K.-H.; Kappes, A.; Karg, T.; Karle, A.; Kenny, P.; Kiryluk, J.; Kislat, F.; Klein, S. R.; Köhne, J.-H.; Kohnen, G.; Kolanoski, H.; Köpke, L.; Koskinen, D. J.; Kowalski, M.; Kowarik, T.; Krasberg, M.; Kroll, G.; Kurahashi, N.; Kuwabara, T.; Labare, M.; Laihem, K.; Landsman, H.; Larson, M. J.; Lauer, R.; Lünemann, J.; Madsen, J.; Marotta, A.; Maruyama, R.; Mase, K.; Matis, H. S.; Meagher, K.; Merck, M.; Mészáros, P.; Meures, T.; Miarecki, S.; Middell, E.; Milke, N.; Miller, J.; Montaruli, T.; Morse, R.; Movit, S. M.; Nahnhauer, R.; Nam, J. W.; Naumann, U.; Nygren, D. R.; Odrowski, S.; Olivas, A.; Olivo, M.; O'Murchadha, A.; Panknin, S.; Paul, L.; Pérez de los Heros, C.; Petrovic, J.; Piegsa, A.; Pieloth, D.; Porrata, R.; Posselt, J.; Price, P. B.; Przybylski, G. T.; Rawlins, K.; Redl, P.; Resconi, E.; Rhode, W.; Ribordy, M.; Richman, M.; Rodrigues, J. P.; Rothmaier, F.; Rott, C.; Ruhe, T.; Rutledge, D.; Ruzybayev, B.; Ryckbosch, D.; Sander, H.-G.; Santander, M.; Sarkar, S.; Schatto, K.; Schmidt, T.; Schönwald, A.; Schukraft, A.; Schultes, A.; Schulz, O.; Schunck, M.; Seckel, D.; Semburg, B.; Seo, S. H.; Sestayo, Y.; Seunarine, S.; Silvestri, A.; Spiczak, G. M.; Spiering, C.; Stamatikos, M.; Stanev, T.; Stezelberger, T.; Stokstad, R. G.; Stößl, A.; Strahler, E. A.; Ström, R.; Stüer, M.; Sullivan, G. W.; Swillens, Q.; Taavola, H.; Taboada, I.; Tamburro, A.; Tepe, A.; Ter-Antonyan, S.; Tilav, S.; Toale, P. A.; Toscano, S.; Tosi, D.; van Eijndhoven, N.; Vandenbroucke, J.; Van Overloop, A.; van Santen, J.; Vehring, M.; Voge, M.; Walck, C.; Waldenmaier, T.; Wallraff, M.; Walter, M.; Weaver, Ch.; Wendt, C.; Westerhoff, S.; Whitehorn, N.; Wiebe, K.; Wiebusch, C. H.; Williams, D. R.; Wischnewski, R.; Wissing, H.; Wolf, M.; Wood, T. R.; Woschnagg, K.; Xu, C.; Xu, D. L.; Xu, X. W.; Yanez, J. P.; Yodh, G.; Yoshida, S.; Zarzhitsky, P.; Zoll, M.

2012-05-01

The IceCube neutrino observatory in operation at the South Pole, Antarctica, comprises three distinct components: a large buried array for ultrahigh energy neutrino detection, a surface air shower array, and a new buried component called DeepCore. DeepCore was designed to lower the IceCube neutrino energy threshold by over an order of magnitude, to energies as low as about 10 GeV. DeepCore is situated primarily 2100 m below the surface of the icecap at the South Pole, at the bottom center of the existing IceCube array, and began taking physics data in May 2010. Its location takes advantage of the exceptionally clear ice at those depths and allows it to use the surrounding IceCube detector as a highly efficient active veto against the principal background of downward-going muons produced in cosmic-ray air showers. DeepCore has a module density roughly five times higher than that of the standard IceCube array, and uses photomultiplier tubes with a new photocathode featuring a quantum efficiency about 35% higher than standard IceCube PMTs. Taken together, these features of DeepCore will increase IceCube's sensitivity to neutrinos from WIMP dark matter annihilations, atmospheric neutrino oscillations, galactic supernova neutrinos, and point sources of neutrinos in the northern and southern skies. In this paper we describe the design and initial performance of DeepCore.

The Design and Performance of IceCube DeepCore

NASA Technical Reports Server (NTRS)

Stamatikos, M.

2012-01-01

The IceCube neutrino observatory in operation at the South Pole, Antarctica, comprises three distinct components: a large buried array for ultrahigh energy neutrino detection, a surface air shower array, and a new buried component called DeepCore. DeepCore was designed to lower the IceCube neutrino energy threshold by over an order of magnitude, to energies as low as about 10 GeV. DeepCore is situated primarily 2100 m below the surface of the icecap at the South Pole, at the bottom center of the existing IceCube array, and began taking pbysics data in May 2010. Its location takes advantage of the exceptionally clear ice at those depths and allows it to use the surrounding IceCube detector as a highly efficient active veto against the principal background of downward-going muons produced in cosmic-ray air showers. DeepCore has a module density roughly five times higher than that of the standard IceCube array, and uses photomultiplier tubes with a new photocathode featuring a quantum efficiency about 35% higher than standard IceCube PMTs. Taken together, these features of DeepCore will increase IceCube's sensitivity to neutrinos from WIMP dark matter annihilations, atmospheric neutrino oscillations, galactic supernova neutrinos, and point sources of neutrinos in the northern and southern skies. In this paper we describe the design and initial performance of DeepCore.

Rapid changes in ice core gas records - Part 1: On the accuracy of methane synchronisation of ice cores

NASA Astrophysics Data System (ADS)

Köhler, P.

2010-08-01

Methane synchronisation is a concept to align ice core records during rapid climate changes of the Dansgaard/Oeschger (D/O) events onto a common age scale. However, atmospheric gases are recorded in ice cores with a log-normal-shaped age distribution probability density function, whose exact shape depends mainly on the accumulation rate on the drilling site. This age distribution effectively shifts the mid-transition points of rapid changes in CH4 measured in situ in ice by about 58% of the width of the age distribution with respect to the atmospheric signal. A minimum dating uncertainty, or artefact, in the CH4 synchronisation is therefore embedded in the concept itself, which was not accounted for in previous error estimates. This synchronisation artefact between Greenland and Antarctic ice cores is for GRIP and Byrd less than 40 years, well within the dating uncertainty of CH4, and therefore does not calls the overall concept of the bipolar seesaw into question. However, if the EPICA Dome C ice core is aligned via CH4 to NGRIP this synchronisation artefact is in the most recent unified ice core age scale (Lemieux-Dudon et al., 2010) for LGM climate conditions of the order of three centuries and might need consideration in future gas chronologies.

The Sublimation Rate of CO2 Under Simulated Mars Conditions and the Possible Climatic Implications

NASA Astrophysics Data System (ADS)

Bryson, Kathryn; Chevrier, V.; Roe, L.; White, K.; Blackburn, D.

2008-09-01

In order to understand the behavior of CO2 on Mars, we have studied the sublimation of dry ice under simulated martian conditions. Our experiments resulted in an average sublimation rate for CO2 ice of 1.20 ± 0.27 mm h-1. These results are very close to those observed of the martian polar caps retreat, and suggest a common process for the sublimation mechanism on Mars and in our chamber. Based on these results we created a model where irradiance from the sun is the primary source of heat on the martian polar surface. Our model predicts a 32 cm offset between the amount of CO2 ice sublimated and deposited in the southern polar region. The eccentricity of the martian orbit causes the southern hemisphere to sublimate more then it deposits back during one martian year. We have compared MOC and HiRISE images from approximately the same season (Ls 285.57º and 289.5º, respectively) from three martian years apart. These images indicate an average sublimation rate of 0.43 ± 0.04 m y-1, very close to the 0.32 m y-1 predicted by our model. Due to the length of Mars’ precession cycle, 93,000 martian years, it will take an extensive amount of time for the equinoxes to change. Therefore, we predict that the CO2 of the south polar cap will migrate entirely to the northern polar cap before such changes could occur. If the CO2 ice is only a thin layer above a much thicker water ice layer, this could expose large amounts of water ice, having a drastic climactic affect.

IceChrono v1: a probabilistic model to compute a common and optimal chronology for several ice cores

NASA Astrophysics Data System (ADS)

Parrenin, Frédéric

2015-04-01

Polar ice cores provide exceptional archives of past environmental conditions. The dating of ice cores is essential to interpret the paleo records that they contain, but it is a complicated problem since it involves different dating methods. Here I present IceChrono v1, a new probabilistic model to combine different kinds of chronological information to obtain a common and optimized chronology for several ice cores, as well as its uncertainty. It is based on the inversion of three quantities: the surface accumulation rate, the Lock-In Depth (LID) of air bubbles and the vertical thinning function. The chronological information used are: models of the sedimentation process (accumulation of snow, densification of snow into ice and air trapping, ice flow), ice and gas dated horizons, ice and gas dated depth intervals, Δdepth observations (depth shift between synchronous events recorded in the ice and in the air), stratigraphic links in between ice cores (ice-ice, air-air or mix ice-air and air-ice links). The optimization problem is formulated as a least squares problems, that is, all densities of probabilities are assumed gaussian. It is numerically solved using the Levenberg-Marquardt algorithm and a numerical evaluation of the model's Jacobian. IceChrono is similar in scope to the Datice model, but has differences from the mathematical, numerical and programming point of views. I apply IceChrono on an AICC2012-like experiment and I find similar results than Datice within a few centuries, which is a confirmation of both IceChrono and Datice codes. IceChrono v1 is freely available under the GPL v3 open source license.

Elevation Change of Drangajokull, Iceland, from Cloud-Cleared ICESat Repeat Profiles and GPS Ground-Survey Data

NASA Technical Reports Server (NTRS)

Shuman, Christopher A.; Sigurdsson, Oddur; Williams, Richard, Jr.; Hall, Dorothy K.

2009-01-01

Located on the Vestfirdir Northwest Fjords), DrangaJokull is the northernmost ice map in Iceland. Currently, the ice cap exceeds 900 m in elevation and covered an area of approx.l46 sq km in August 2004. It was about 204 sq km in area during 1913-1914 and so has lost mass during the 20th century. Drangajokull's size and accessibility for GPS surveys as well as the availability of repeat satellite altimetry profiles since late 2003 make it a good subject for change-detection analysis. The ice cap was surveyed by four GPS-equipped snowmobiles on 19-20 April 2005 and has been profiled in two places by Ice, Cloud. and land Elevation Satellite (ICESat) 'repeat tracks,' fifteen times from late to early 2009. In addition, traditional mass-balance measurements have been taken seasonally at a number of locations across the ice cap and they show positive net mass balances in 2004/2005 through 2006/2007. Mean elevation differences between the temporally-closest ICESat profiles and the GPS-derived digital-elevation model (DEM)(ICESat - DEM) are about 1.1 m but have standard deviations of 3 to 4 m. Differencing all ICESat repeats from the DEM shows that the overall elevation difference trend since 2003 is negative with losses of as much as 1.5 m/a from same season to same season (and similar elevation) data subsets. However, the mass balance assessments by traditional stake re-measurement methods suggest that the elevation changes where ICESat tracks 0046 and 0307 cross Drangajokull are not representative of the whole ice cap. Specifically, the area has experienced positive mass balance years during the time frame when ICESat data indicates substantial losses. This analysis suggests that ICESat-derived elevations may be used for multi-year change detection relative to other data but suggests that large uncertainties remain. These uncertainties may be due to geolocation uncertainty on steep slopes and continuing cloud cover that limits temporal and spatial coverage across the area.

Impacts of Recent Warming and the 2015/2016 El Niño on Tropical Peruvian Ice Fields

NASA Astrophysics Data System (ADS)

Thompson, L. G.; Davis, M. E.; Mosley-Thompson, E.; Beaudon, E.; Porter, S. E.; Kutuzov, S.; Lin, P.-N.; Mikhalenko, V. N.; Mountain, K. R.

2017-12-01

Data collected between 1974 and 2016 from snow pits and core samples from two Peruvian ice fields demonstrate the effect of the recent warming over the tropical Andes, augmented by El Niño, on the preservation of the climate record. As the 0°C isotherm is approaching the summit of the Quelccaya ice cap in the Andes of southern Peru (5,670 meters above sea level (masl)), the distinctive seasonal δ18O oscillations in the fresh snow deposited within each thermal year are attenuated at depth due to melting and percolation through the firn. This has become increasingly pronounced over 43 years. In the Andes of northern Peru, the ice field on the col of Nevado Huascarán (6050 masl) has retained its seasonal δ18O variations at depth due to its higher elevation. During the 2015/2016 El Niño, snow on Quelccaya and Huascarán was isotopically (δ18O) enriched and the net sum of accumulation over the previous year (NSA) was below the mean for non-El Niño years, particularly on Quelccaya (up to 64% below the mean) which was more pronounced than the NSA decrease during the comparable 1982/1983 El Niño. Interannual large-scale oceanic and middle to upper-level atmospheric temperatures influence δ18O in precipitation on both ice fields, although the influences are variably affected by strong El Niño-Southern Oscillation events, especially on Quelccaya. The rate of ice wastage along Quelccaya's margin was dramatically higher during 2015/2016 compared with that of the previous 15 years, suggesting that warming from future El Niños may accelerate mass loss on Peruvian glaciers.

The hemispherical asymmetry of the residual polar caps on Mars

NASA Technical Reports Server (NTRS)

Lindner, Bernhard Lee

1991-01-01

A model of the polar caps of Mars was created which allows: (1) for light penetration into the cap; (2) ice albedo to vary with age, latitude, hemisphere, dust content, and solar zenith angle; and (3) for diurnal variability. The model includes the radiative effects of clouds and dust, and heat transport as represented by a thermal wind. The model reproduces polar cap regression data very well, including the survival of CO2 frost at the south pole and reproduces the general trend in the Viking Lander pressure data.

Origin, Bulk Chemical Composition and Physical Structure of the Galilean Satellites of Jupiter: A Post-Galileo Analysis

NASA Technical Reports Server (NTRS)

Prentice, A. J. R.

1999-01-01

The origin of Jupiter and the Galilean satellite system is examined in the light of the new data that has been obtained by the NASA Galileo Project. In particular, special attention is given to a theory of satellite origin which was put forward at the start of the Galileo Mission and on the basis of which several predictions have now been proven successful. These predictions concern the chemical composition of Jupiter's atmosphere and the physical structure of the satellites. According to the proposed theory of satellite origin, each of the Galilean satellites formed by chemical condensation and gravitational accumulation of solid grains within a concentric family of orbiting gas rings. These rings were cast off equatorially by the rotating proto-Jovian cloud (PJC which contracted gravitationally to form Jupiter some 4 1/2 billion years ago. The PJC formed from the gas and grains left over from the gas ring that had been shed at Jupiter's orbit by the contracting proto-solar cloud (PSC Supersonic turbulent convection provides the means for shedding discrete gas rings. The temperatures T (sub n) of the system of gas rings shed by the PSC and PJC vary with their respective mean orbital radii R (sub n) (n = 0, 1,2,...) according as T (sub n) proportional to R (sub n) (exp -0.9). If the planet Mercury condenses at 1640 K, so accounting for the high density of that planet via a process of chemical fractionation between iron and silicates, then T (sub n) at Jupiter's orbit is 158 K. Only 35% of the water vapour condenses out. Thus fractionation between rock and ice, together with an enhancement in the abundance of solids relative to gas which takes place through gravitational sedimentation of solids onto the mean orbit of the gas ring, ensures nearly equal proportions of rock and ice in each of Ganymede and Callisto. Io and Europa condense above the H20 ice point and consist solely of hydrated rock (h-rock). The Ganymedan condensate consists of h-rock and H20 ice. For Callisto, NH3 ice makes up -5% of the condensate mass next to h-rock (approximately 50%) and H2O ice (approximately 45%). Detailed thermal and structural models for each of Europa, Ganymede and Callisto are constructed on the basis of the above initial bulk chemical compositions. For Europa (E), a predicted 2-zone model consisting of a dehydrated rock core of mass 0.912 M (sub E) and a 150 km thick frozen mantle of salty H2O yields a moment-of-inertia coefficient which matches the Galileo Orbiter gravity measurement. For Ganymede (G), a 3-zone model possessing an inner core of solid FeS and mass approximately 0.116 M (sub G), and an outer H2O ice mantle of mass approximately 0.502 M (sub G) is needed to explain the gravity data. Ganymede's native magnetic field was formed by thermoremanent magnetization of Fe3O4. A new Callisto (C) model is proposed consisting of a core of mass 0.826 M (sub C) containing a uniform mixture of h-rock (60% by mass) and H2O and NH3 ices, and capped by a mantle of pure ice. This model may have the capacity to yield a thin layer of liquid NH3 (raised dot) 2H2O at the core boundary, in line with Galileo's discovery of an induced magnetic field.

Seasonally-Active Water on Mars: Vapour, Ice, Adsorbate, and the Possibility of Liquid

NASA Astrophysics Data System (ADS)

Richardson, M. I.

2002-12-01

Seasonally-active water can be defined to include any water reservoir that communicates with other reservoirs on time scales of a year or shorter. It is the interaction of these water reservoirs, under the influence of varying solar radiation and in conjunction with surface and atmospheric temperatures, that determines the phase-stability field for water at the surface, and the distribution of water in various forms below, on, and above the surface. The atmosphere is the critical, dynamical link in this cycling system, and also (fortunately) one of the easiest to observe. Viking and Mars Global Surveyor observations paint a strongly asymmetric picture of the global seasonal water cycle, tied proximately to planetary eccentricity, and the existence of residual ice caps of different composition at the two poles. The northern summer experiences the largest water vapour columns, and is associated with sublimation from the northern residual water ice cap. The southern summer residual carbon dioxide ice cap is cold trap for water. Asymmetry in the water cycle is an unsolved problem. Possible solutions may involve the current timing of perihelion (the water cap resides at the pole experiencing the longer but cooler summer), the trapping of water ice in the northern hemisphere by tropical water ice clouds, and the bias in the annual-average, zonal-mean atmospheric circulation resulting from the zonal-mean difference in the elevation of the northern and southern hemispheres. Adsorbed and frozen water have proven harder to constrain. Recent Odyssey Gamma Ray Spectrometer results suggest substantial ground ice in the mid- and high-latitudes, but this water is likely below the seasonal skin depth for two reasons: the GRS results are best fit with such a model, and GCM models of the water cycle produce dramatically unrealistic atmospheric vapour distributions when such a very near surface, GRS-like distribution is initialized - ultimately removing the water to the northern and southern caps. Similar climate-models of the water cycle also do not need much exchangeable adsorbed water in order to explain the observed vapour distributions. The possibility of liquid water is tantalizing, but difficult to definitively judge. On scales greater than a meter or so, Mars is most definitely well away from the water triple point--although the surface pressure can exceed 6.1 mbars, the partial pressure of water vapor (to which the triple point refers) is at best orders of magnitude lower. Several careful studies have shown, however, that locally transient (meta-stable) liquid is possible, if the net heating of ice deposits is high enough. This process is aided if the total surface pressure exceeds 6.1mbar (this prevents boiling, or the explosive loss of vapour into the atmosphere) or if the liquid is covered by a thin ice shell, and is only possible if surface temperatures exceed 273K (for pure water, or the appropriate eutectic for brines) and if ice is present. The former challenge is much easier to meet than the latter. The melt scenario requires that ice deposited in winter must be protected from sublimation as surface temperatures increase in spring, but then exposed to the peak of solar heating in summer. Available spacecraft observations of seasonal water will be discussed with the aid of GCM model simulations, and examined in the context of water distributions and phases.

Determination of lead isotopes in a new Greenland deep ice core at the sub-picogram per gram level by thermal ionization mass spectrometry using an improved decontamination method.

PubMed

Han, Changhee; Burn-Nunes, Laurie J; Lee, Khanghyun; Chang, Chaewon; Kang, Jung-Ho; Han, Yeongcheol; Hur, Soon Do; Hong, Sungmin

2015-08-01

An improved decontamination method and ultraclean analytical procedures have been developed to minimize Pb contamination of processed glacial ice cores and to achieve reliable determination of Pb isotopes in North Greenland Eemian Ice Drilling (NEEM) deep ice core sections with concentrations at the sub-picogram per gram level. A PL-7 (Fuso Chemical) silica-gel activator has replaced the previously used colloidal silica activator produced by Merck and has been shown to provide sufficiently enhanced ion beam intensity for Pb isotope analysis for a few tens of picograms of Pb. Considering the quantities of Pb contained in the NEEM Greenland ice core and a sample weight of 10 g used for the analysis, the blank contribution from the sample treatment was observed to be negligible. The decontamination and analysis of the artificial ice cores and selected NEEM Greenland ice core sections confirmed the cleanliness and effectiveness of the overall analytical process. Copyright © 2015 Elsevier B.V. All rights reserved.

South Polar Cap

NASA Technical Reports Server (NTRS)

2005-01-01

8 December 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows landforms created by sublimation processes on the south polar residual cap of Mars. The bulk of the ice in the south polar residual cap is frozen carbon dioxide.

Location near: 86.6oS, 342.2oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

Methane seeps along boundaries of arctic permafrost thaw and melting glaciers

NASA Astrophysics Data System (ADS)

Anthony, P.; Walter Anthony, K. M.; Grosse, G.; Chanton, J.

2014-12-01

Methane, a potent greenhouse gas, accumulates in subsurface hydrocarbon reservoirs. In the Arctic, impermeable icy permafrost and glacial overburden form a 'cryosphere cap' that traps gas leaking from these reservoirs, restricting flow to the atmosphere. We document the release of geologic methane to the atmosphere from abundant gas seeps concentrated along boundaries of permafrost thaw and receding glaciers in Alaska. Through aerial and ground surveys we mapped >150,000 seeps identified as bubbling-induced open holes in lake ice. Subcap methane seeps had anomalously high fluxes, 14C-depletion, and stable isotope values matching known coalbed and thermogenic methane accumulations in Alaska. Additionally, we observed younger subcap methane seeps in Greenland that were associated with ice-sheet retreat since the Little Ice Age. These correlations suggest that in a warming climate, continued disintegration of permafrost, glaciers, and parts of the polar ice sheets will relax pressure on subsurface seals and further open conduits, allowing a transient expulsion of geologic methane currently trapped by the cryosphere cap.

On the use of δ18Oatm for ice core dating

NASA Astrophysics Data System (ADS)

Extier, Thomas; Landais, Amaelle; Bréant, Camille; Prié, Frédéric; Bazin, Lucie; Dreyfus, Gabrielle; Roche, Didier M.; Leuenberger, Markus

2018-04-01

Deep ice core chronologies have been improved over the past years through the addition of new age constraints. However, dating methods are still associated with large uncertainties for ice cores from the East Antarctic plateau where layer counting is not possible. Indeed, an uncertainty up to 6 ka is associated with AICC2012 chronology of EPICA Dome C (EDC) ice core, which mostly arises from uncertainty on the delay between changes recorded in δ18Oatm and in June 21st insolation variations at 65°N used for ice core orbital dating. Consequently, we need to enhance the knowledge of this delay to improve ice core chronologies. We present new high-resolution EDC δ18Oatm record (153-374 ka) and δO2/N2 measurements (163-332 ka) performed on well-stored ice to provide continuous records of δ18Oatm and δO2/N2 between 100 and 800 ka. The comparison of δ18Oatm with the δ18Ocalcite from East Asian speleothems shows that both signals present similar orbital and millennial variabilities, which may represent shifts in the InterTropical Convergence Zone position, themselves associated with Heinrich events. We thus propose to use the δ18Ocalcite as target for δ18Oatm orbital dating. Such a tuning method improves the ice core chronology of the last glacial inception compared to AICC2012 by reconciling NGRIP and mid-latitude climatic records. It is especially marked during Dansgaard-Oeschger 25 where the proposed chronology is 2.2 ka older than AICC2012. This δ18Oatm - δ18Ocalcite alignment method applied between 100 and 640 ka improves the EDC ice core chronology, especially over MIS 11, and leads to lower ice age uncertainties compared to AICC2012.

Dust Records in Ice Cores from the Tibetan Plateau

NASA Astrophysics Data System (ADS)

Wang, N.; Yao, T.; Thompson, L. G.

2014-12-01

Dust plays an important role in the Earth system, and it usually displays largely spatial and temporal variations. It is necessary for us to reconstruct the past variations of dust in different regions to better understand the interactions between dust and environments. Ice core records can reveal the history of dust variations. In this paper, we used the Guliya, Dunde, Malan and Dasuopu ice cores from the Tibetan Plateau to study the spatial distribution, the seasonal variations and the secular trends of dust. It was found that the mean dust concentration was higher by one or two order of magnitudes in the Guliya and Dunde ice cores from the northern Tibetan Plateau than in the Dasuopu ice core from the southern Tibetan Plateau. During the year, the highest dust concentration occurs in the springtime in the northern Tibetan Plateau while in the non-monsoon season in the southern Tibetan Plateau. Over the last millennium, the Dasuopu ice core record shows that the 1270s~1380s and 1870s~1990s were the two epochs with high dust concentration. However, the Malan ice core from the northern Tibetan Plateau indicates that high dust concentration occurred in the 1130s~1550s and 1770s~1940s. Interestingly, climatic and environmental records of the ice cores from the Tibetan Plateau reflected that the correlation between dust concentration and air temperature was strongly positive in the southern Plateau while negative in the northern Plateau over the last millennium. This implies that climatic and environmental changes existed considerable differences in the different parts of the Plateau. Moreover, four Asian megadroughts occurred in 1638~1641, 1756~1758, 1790~1796 and 1876~1878, which caused more than tens millions people died, were revealed clearly by dust record in the Dasuopu ice core.

Initial results from geophysical surveys and shallow coring of the Northeast Greenland Ice Stream (NEGIS)

NASA Astrophysics Data System (ADS)

Vallelonga, P.; Christianson, K.; Alley, R. B.; Anandakrishnan, S.; Christian, J. E. M.; Dahl-Jensen, D.; Gkinis, V.; Holme, C.; Jacobel, R. W.; Karlsson, N. B.; Keisling, B. A.; Kipfstuhl, S.; Kjær, H. A.; Kristensen, M. E. L.; Muto, A.; Peters, L. E.; Popp, T.; Riverman, K. L.; Svensson, A. M.; Tibuleac, C.; Vinther, B. M.; Weng, Y.; Winstrup, M.

2014-07-01

The Northeast Greenland Ice Stream (NEGIS) is the sole interior Greenlandic ice stream. Fast flow initiates near the summit dome, and the ice stream terminates approximately 1000 km downstream in three large outlet glaciers that calve into the Greenland Sea. To better understand this important system, in the summer of 2012 we drilled a 67 m firn core and conducted ground-based radio-echo sounding (RES) and active-source seismic surveys at a site approximately 150 km downstream from the onset of streaming flow (NEGIS firn core, 75°37.61' N, 35°56.49' W). The site is representative of the upper part of the ice stream, while also being in a crevasse-free area for safe surface operations. Annual cycles were observed for insoluble dust, sodium and ammonium concentrations and for electrolytic conductivity, allowing a seasonally resolved chronology covering the past 400 yr. Annual layer thicknesses averaged 0.11 m ice equivalent (i.e.) for the period 1607-2011, although accumulation varied between 0.08 and 0.14 m i.e., likely due to flow-related changes in surface topography. Tracing of RES layers from the NGRIP (North Greenland Ice Core Project) ice core site shows that the ice at NEGIS preserves a climatic record of at least the past 51 kyr. We demonstrate that deep ice core drilling in this location can provide a reliable Holocene and late-glacial climate record, as well as helping to constrain the past dynamics and ice-lithosphere interactions of the Greenland Ice Sheet.

Dating of 30m ice cores drilled by Japanese Antarctic Research Expedition and environmental change study

NASA Astrophysics Data System (ADS)

Motoyama, H.; Suzuki, T.; Fukui, K.; Ohno, H.; Hoshina, Y.; Hirabayashi, M.; Fujita, S.

2017-12-01

1. Introduction It is possible to reveal the past climate and environmental change from the ice core drilled in polar ice sheet and glaciers. The 54th Japanese Antarctic Research Expedition conducted several shallow core drillings up to 30 m depth in the inland and coastal areas of the East Antarctic ice sheet. Ice core sample was cut out at a thickness of about 5 cm in the cold room of the National Institute of Polar Research, and analyzed ion, water isotope, dust and so one. We also conducted dielectric profile measurement (DEP measurement). The age as a key layer of large-scale volcanic explosion was based on Sigl et al. (Nature Climate Change, 2014). 2. Inland ice core Ice cores were collected at the NDF site (77°47'14"S, 39°03'34"E, 3754 m.a.s.l.) and S80 site (80°00'00"S, 40°30'04"E, 3622 m.a.s.l.). Dating of ice core was done as follows. Calculate water equivalent from core density. Accumulate water equivalent from the surface. Approximate the relation of depth - cumulative water equivalent by a quartic equation. We determined the key layer with nssSO42 - peak corresponding to several large volcanic explosions. The accumulation rate was kept constant between the key layers. As a result, NDF was estimated to be around 1360 AD and S80 was estimated to be around 1400 AD in the deepest ice core. 3. Coastal ice core An ice core was collected at coastal H15 sites (69°04'10"S, 40°44'51"E, 1030 m.a.s.l.). Dating of ice core was done as follows. Calculate water equivalent from ice core density. Accumulate water equivalent from the surface. Approximate the relation of depth - cumulative water equivalent by a quartic equation. Basically we decided to summer (December) and winter (June) due to the seasonal change of the water isotope (δD or δ18O). In addition to the seasonal change of isotope, confirm the following. Maximum of SO42- / Na +, which is earlier in time than the maximum of water isotope. Maximum of MSA at about the same time as the maximum of the water isotope. Na+ is maximal immediately after the local maximum of the water isotope. The deepest age was estimated to be around 1940 AD. 4. Example of results In the inland area, the annual average surface mass balance decreased from 1450 to 1850 AD, but it has increased since 1850 AD. The annual mass balance of coastal H15 is consistent with the result of snow stake measurement.

Chemistry of microparticles trapped in last glacial period ice of EPICA-DML deep ice core

NASA Astrophysics Data System (ADS)

Nedelcu, Aneta F.; Faria, Sérgio H.; Kipfstuhl, Sepp; Kuhs, Werner F.

2010-05-01

The EDML ice core, drilled within the framework of the European project for Ice Coring in Antarctica, (EPICA), in the interior of Dronning Maud Land, DML, Antarctica (at 75°S, 0°E), is the first deep ice core in the Atlantic sector of the Southern Ocean region that provides higher-resolution atmosphere and climate records for the last glacial period, when compared with other ice cores retrieved from the East Antarctic plateau [1]. The chemical impurities embedded in the ice matrix of an ice sheet are basic proxies for climate reconstruction, and their concentration and composition usually determine the occurrence of distinct (cloudy or clear) strata in the ice sheet structure. The easiest observable impurities in polar ice are air bubbles. But a considerable amount of the impurities trapped inside ice layers are observed as microscopic deposits of solid (soluble or insoluble) particles, not bigger than a few micra in size, called microinclusions. Layers of ice with a high content of (micro)inclusions are in general called cloudy bands and are considered to have been formed from the precipitations deposited during colder periods. Roughly, we expect that the colder the climate during the time the snow accumulated, the cloudier the ice stratum that forms afterwards [2]. Mainly by means of in-situ micro-Raman spectroscopy, it has been shown that in Antarctic glacial ice the soluble microinclusions occur mostly as sulphate and nitrate salts [3], while in Arctic ice more commonly as carbonate salts [4]. These findings could be explained in terms of different aerosol compositions determined by the specific regional environments and climatic conditions [5]. Regarding the insoluble particles that might exist in natural ice, with higher frequency in ice layers formed during glacial type stages, the general findings classify them in the (alumino)silicate mineralogical class [6]. Microinclusions existent in solid samples taken from clear and cloudy ice layers, corresponding to the Marine Isotope Stage 2 of the EDML deep ice core, were subjected to in-situ Raman scattering measurements. The overall results [7] resemble the observations [8] that a high content of sulphate anions could characterize the chemical composition of the aerosols arriving at the EDML ice core drilling site. Many microparticles provided a Raman signal different from what would be expected if only simple compounds were forming them (and dissimilar with those in [3]). For example, it resulted that in the same microinclusion nonequivalent sulphate groups are present (20% of all), or that sulphate and silicate anions coexist (10% of all). On the one hand, this can be explained by a simple post-depositional aggregation of very small inclusions of simple sulphate salts into microclusters. On the other hand the results might be interpreted in terms of aerosol chemistry, when a mixture of sulphate salts could have been already formed prior to deposition. This work will offer answers for questions related with the existence of a post-depositional alteration of the initial impurities deposited in the LGP ice at the EDML ice core drilling site. [1] EPICA community members (2006). One-to-one coupling of glacial climate variability in Greenland and Antarctica, Nature, 444, 195-198. [2] Faria, S.H., Freitag, J., Kipfstuhl, S. (2010) Polar ice structure and the integrity of ice-core paleoclimate records, Quaternary Sci. Rev., 29, 1-2, 338-351. [3] Ohno H., M. Igarashi, T. Hondoh. 2005. Salt inclusions in polar ice core: Location and chemical form of water-soluble impurities, Earth Planet.Sci. Lett., 232, 171-178. [4] Sakurai T., Iizuka Y., Horikawa S., Johnsen S., Dahl-Jensen D., Steffensen J.P., Hondoh T. (2009). Direct observation of salts as micro-inclusions in the Greenland GRIP ice core. J. Glaciol., 55, 193, 777-783. [5] Iizuka Y., Horikawa S., Sakurai T., Johnson S, Dahl-Jensen D., Steffensen J.P., Hondoh T. (2008). A relationship between ion balance and the chemical compounds of salt inclusions found in the Greenland Ice Core Project and Dome Fuji ice cores. J. Geophys. Res., 113, D7, D07303. [6] Iizuka, Y., Miyake T., Hirabayashi M., Suzuki T., Matoba S., Motoyama H., Fujii Y., Hondoh T. (2009). Constituent elements of insoluble and non-volatile particles during the Last Glacial Maximum exhibited in the Dome Fuji (Antarctica) ice core. J. Glaciol., 55, 191, 552-562. [7] Nedelcu A.F., Kipfstuhl S., Faria S.H., Kuhs W.F. Microinclusions in clear and cloudy (MIS2) EDML ice revealed by Raman spectroscopy. In preparation for J. Glaciol. [8] Weller R., Wagenbach D. (2007) Year-round chemical aerosol records in continental Antarctica obtained by automatic samplings. Tellus 59, 755-765.

Cool Science Explains a Warming World: Using Ice Core Science to Bridge the Gap Between Researchers and the K-12 Classroom

NASA Astrophysics Data System (ADS)

Huffman, L. T.

2017-12-01

Changing ice has urgent implications for people around the world. The Ice Drilling Program Office (IDPO) provides scientific leadership and oversight of ice coring and drilling activities funded by the US National Science Foundation and also has goals to enhance education and communication of current research information. In a time when misinformation is rampant and climate change science is suspect, it is essential that students receive accurate scientific information and engage in learning activities that model complex ideas through engaging and age appropriate ways, while also learning to validate and recognize reliable sources. The IDPO Education and Outreach (EO) office works to create resources, activities and professional development that bridge the gap between ice core science research and educators and their students. Ice core science is on the cutting edge of new discoveries about climate change and understanding better the past to predict the future. Hands-on inquiry activities based on ice core data allow teachers to lead their students to new discoveries about climate secrets hidden deep in the ice. Capitalizing on the inherent interest in the extremes of the Polar Regions, IDPO materials engage students in activities aligned with NGSS standards. Ice drilling technologies make an ideal platform for intertwining engineering concepts and practices with science research to meet the SEP (Science and Engineering Practices) in the NGSS. This session will highlight how the IDPO EO office has built a community of ice core scientists willing to take part in education and outreach projects and events and share some of the resources available to K-12 educators. We will highlight some of the successes and lessons learned as we continually evolve our work toward more effective science education and communication highlighting ice core and climate change science.

Vegetation and Climate Changes in Patagonia (46°S) during the Last 20 kyr cal. BP from South East Pacific MD 07 3088 Core

NASA Astrophysics Data System (ADS)

Montade, V.; Combourieu Nebout, N.; Siani, G.; Michel, E.; Kissel, C.; Carel, M.; Mulsow, S.

2010-12-01

The Chilean Patagonia (41°S to 56°S) crossed by the Andes from north to south represents a critical topographic constraint on atmospheric and oceanic systems, and the only continental landmass intercepting the entire Southern Westerlies Wind (SHW) belt in southern hemisphere. Therefore, the southern Chile is a key-area to study the paleoclimate changes and, to understand the synoptic scale ocean-atmospheric circulation systems of the mid to high southern latitudes. However, several questions remain partly unsolved: Is there abrupt reversal event during the Last Glacial-Interglacial transition (LGIT)? Is there a shift or an intensification of the SHW? When begin the Holocene onset? What are the inter or intra hemispheric climatic links? In this aim, we present here a detailed pollen record from the deep-sea core MD 07 3088 (46°04’S; 76°05’W, 1536 m) near Taitao peninsula, taken during the “Pachiderme” cruise (MD 159) within the IMAGES (International MArine Global changES) program (Kissel et al., 2007). The age model (Siani et al., in press) is based upon stable oxygen isotopes of planktonic foraminifera G. bulloïdes coupled to ten AMS 14C measurements performed on planktonic foraminifera and four tephrochronological markers attributed to the Hudson volcano (Haberle and Lumley, 1998). The pollen record expresses vegetation changes and thus climate variations during the last 20 kyr cal. BP. Several vegetation phases are observed during the LGIT and the Holocene onset: Before 18 kyr, the low diversity and pollen influx show the reduced vegetation due to the Patagonian Ice Cap extension and cold temperature. From 17.5 to 14.5 kyr, the diversity and pollen influx increase mark the vegetation development linked to the ice cap melting and temperature increase. From 14.5 to 12 kyr, the Astelia development illustrates the Magellanic Moorland extension and humid conditions linked to the SHW. Later 11.5 kyr, the forest diversification expresses the Holocene onset. Finally, comparison between the pollen and the oxygen isotope record from Antarctic core (EDML, Lemieux-Dudon et al., 2010) shows direct relationships between the vegetation changes and the major climatic events of the LGIT.

Microbial diversity on Icelandic glaciers and ice caps.

PubMed

Lutz, Stefanie; Anesio, Alexandre M; Edwards, Arwyn; Benning, Liane G

2015-01-01

Algae are important primary colonizers of snow and glacial ice, but hitherto little is known about their ecology on Iceland's glaciers and ice caps. Due do the close proximity of active volcanoes delivering large amounts of ash and dust, they are special ecosystems. This study provides the first investigation of the presence and diversity of microbial communities on all major Icelandic glaciers and ice caps over a 3 year period. Using high-throughput sequencing of the small subunit ribosomal RNA genes (16S and 18S), we assessed the snow community structure and complemented these analyses with a comprehensive suite of physical-, geo-, and biochemical characterizations of the aqueous and solid components contained in snow and ice samples. Our data reveal that a limited number of snow algal taxa (Chloromonas polyptera, Raphidonema sempervirens and two uncultured Chlamydomonadaceae) support a rich community comprising of other micro-eukaryotes, bacteria and archaea. Proteobacteria and Bacteroidetes were the dominant bacterial phyla. Archaea were also detected in sites where snow algae dominated and they mainly belong to the Nitrososphaerales, which are known as important ammonia oxidizers. Multivariate analyses indicated no relationships between nutrient data and microbial community structure. However, the aqueous geochemical simulations suggest that the microbial communities were not nutrient limited because of the equilibrium of snow with the nutrient-rich and fast dissolving volcanic ash. Increasing algal secondary carotenoid contents in the last stages of the melt seasons have previously been associated with a decrease in surface albedo, which in turn could potentially have an impact on the melt rates of Icelandic glaciers.

Microbial diversity on Icelandic glaciers and ice caps

PubMed Central

Lutz, Stefanie; Anesio, Alexandre M.; Edwards, Arwyn; Benning, Liane G.

2015-01-01

Algae are important primary colonizers of snow and glacial ice, but hitherto little is known about their ecology on Iceland's glaciers and ice caps. Due do the close proximity of active volcanoes delivering large amounts of ash and dust, they are special ecosystems. This study provides the first investigation of the presence and diversity of microbial communities on all major Icelandic glaciers and ice caps over a 3 year period. Using high-throughput sequencing of the small subunit ribosomal RNA genes (16S and 18S), we assessed the snow community structure and complemented these analyses with a comprehensive suite of physical-, geo-, and biochemical characterizations of the aqueous and solid components contained in snow and ice samples. Our data reveal that a limited number of snow algal taxa (Chloromonas polyptera, Raphidonema sempervirens and two uncultured Chlamydomonadaceae) support a rich community comprising of other micro-eukaryotes, bacteria and archaea. Proteobacteria and Bacteroidetes were the dominant bacterial phyla. Archaea were also detected in sites where snow algae dominated and they mainly belong to the Nitrososphaerales, which are known as important ammonia oxidizers. Multivariate analyses indicated no relationships between nutrient data and microbial community structure. However, the aqueous geochemical simulations suggest that the microbial communities were not nutrient limited because of the equilibrium of snow with the nutrient-rich and fast dissolving volcanic ash. Increasing algal secondary carotenoid contents in the last stages of the melt seasons have previously been associated with a decrease in surface albedo, which in turn could potentially have an impact on the melt rates of Icelandic glaciers. PMID:25941518

Calibrating a surface mass-balance model for Austfonna ice cap, Svalbard

NASA Astrophysics Data System (ADS)

Schuler, Thomas Vikhamar; Loe, Even; Taurisano, Andrea; Eiken, Trond; Hagen, Jon Ove; Kohler, Jack

2007-10-01

Austfonna (8120 km2) is by far the largest ice mass in the Svalbard archipelago. There is considerable uncertainty about its current state of balance and its possible response to climate change. Over the 2004/05 period, we collected continuous meteorological data series from the ice cap, performed mass-balance measurements using a network of stakes distributed across the ice cap and mapped the distribution of snow accumulation using ground-penetrating radar along several profile lines. These data are used to drive and test a model of the surface mass balance. The spatial accumulation pattern was derived from the snow depth profiles using regression techniques, and ablation was calculated using a temperature-index approach. Model parameters were calibrated using the available field data. Parameter calibration was complicated by the fact that different parameter combinations yield equally acceptable matches to the stake data while the resulting calculated net mass balance differs considerably. Testing model results against multiple criteria is an efficient method to cope with non-uniqueness. In doing so, a range of different data and observations was compared to several different aspects of the model results. We find a systematic underestimation of net balance for parameter combinations that predict observed ice ablation, which suggests that refreezing processes play an important role. To represent these effects in the model, a simple PMAX approach was included in its formulation. Used as a diagnostic tool, the model suggests that the surface mass balance for the period 29 April 2004 to 23 April 2005 was negative (-318 mm w.e.).

Ice Core Investigations

ERIC Educational Resources Information Center

Krim, Jessica; Brody, Michael

2008-01-01

What can glaciers tell us about volcanoes and atmospheric conditions? How does this information relate to our understanding of climate change? Ice Core Investigations is an original and innovative activity that explores these types of questions. It brings together popular science issues such as research, climate change, ice core drilling, and air…

A moderate resolution inventory of small glaciers and ice caps surrounding Greenland and the Antarctic peninsula

NASA Astrophysics Data System (ADS)

Chen, C.; Box, J. E.; Hock, R. M.; Cogley, J. G.

2011-12-01

Current estimates of global Mountain Glacier and Ice Caps (MG&IC) mass changes are subject to large uncertainties due to incomplete inventories and uncertainties in land surface classification. This presentation features mitigative efforts through the creation of a MODIS dependent land ice classification system and its application for glacier inventory. Estimates of total area of mountain glaciers [IPCC, 2007] and ice caps (including those in Greenland and Antarctica) vary 15%, that is, 680 - 785 10e3 sq. km. To date only an estimated 40% of glaciers (by area) is inventoried in the World Glacier Inventory (WGI) and made available through the World Glacier Monitoring System (WGMS) and the National Snow and Ice Data Center [NSIDC, 1999]. Cogley [2009] recently compiled a more complete version of WGI, called WGI-XF, containing records for just over 131,000 glaciers, covering approximately half of the estimated global MG&IC area. The glaciers isolated from the conterminous Antarctic and Greenland ice sheets remain incompletely inventoried in WGI-XF but have been estimated to contribute 35% to the MG&IC sea-level equivalent during 1961-2004 [Hock et al., 2009]. Together with Arctic Canada and Alaska these regions alone make up almost 90% of the area that is missing in the global WGI-XF inventory. Global mass balance projections tend to exclude ice masses in Greenland and Antarctica due to the paucity of data with respect to basic inventory base data such as area, number of glaciers or size distributions. We address the need for an accurate Greenland and Antarctic peninsula land surface classification with a novel glacier surface classification and inventory based on NASA Moderate Resolution Imaging Spectroradiometer (MODIS) data gridded at 250 m pixel resolution. The presentation includes a sensitivity analysis for surface mass balance as it depends on the land surface classification. Works Cited +Cogley, J. G. (2009), A more complete version of the World Glacier Inventory, Ann. Glaciol. 50(53). +Hock, R., M. de Woul, V. Radi and M. Dyurgerov, 2009. Mountain glaciers and ice caps around Antarctica make a large sea-level rise contribution. Geophys. Res. Lett. 36, L07501, doi:10.1029/2008GL037020. +IPCC, Climate Change 2007 The Physical Science Basis, 2007. Contribution of working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (eds. Solomon, S. et al.) Cambridge University Press, Cambridge, UK.

Post-glacial variations of sea ice cover and river discharge in the western Laptev Sea (Arctic Ocean) - a high-resolution study over the last 18 ka

NASA Astrophysics Data System (ADS)

Hörner, Tanja; Stein, Ruediger; Fahl, Kirsten

2015-04-01

Here, we provide a high-resolution reconstruction of sea-ice cover variations in the western Laptev Sea, a crucial area in terms of sea-ice production in the Arctic Ocean and a region characterized by huge river discharge. Furthermore, the shallow Laptev Sea was strongly influenced by the post-glacial sea-level rise that should also be reflected in the sedimentary records. The sea Ice Proxy IP25 (Highly-branched mono-isoprenoid produced by sea-ice algae; Belt et al., 2007) was measured in two sediment cores from the western Laptev Sea (PS51/154, PS51/159) that offer a high-resolution composite record over the last 18 ka. In addition, sterols are applied as indicator for marine productivity (brassicasterol, dinosterol) and input of terrigenous organic matter by river discharge into the ocean (campesterol, ß-sitosterol). The sea-ice cover varies distinctly during the whole time period and shows a general increase in the Late Holocene. A maximum in IP25 concentration can be found during the Younger Dryas. This sharp increase can be observed in the whole circumarctic realm (Chukchi Sea, Bering Sea, Fram Strait and Laptev Sea). Interestingly, there is no correlation between elevated numbers of ice-rafted debris (IRD) interpreted as local ice-cap expansions (Taldenkova et al. 2010), and sea ice cover distribution. The transgression and flooding of the shelf sea that occurred over the last 16 ka in this region, is reflected by decreasing terrigenous (riverine) input, reflected in the strong decrease in sterol (ß-sitosterol and campesterol) concentrations. References Belt, S.T., Massé, G., Rowland, S.J., Poulin, M., Michel, C., LeBlanc, B., 2007. A novel chemical fossil of palaeo sea ice: IP25. Organic Geochemistry 38 (1), 16e27. Taldenkova, E., Bauch, H.A., Gottschalk, J., Nikolaev, S., Rostovtseva, Yu., Pogodina, I., Ya, Ovsepyan, Kandiano, E., 2010. History of ice-rafting and water mass evolution at the northern Siberian continental margin (Laptev Sea) during Late Glacial and Holocene times. Quaternary Science Reviews 29 (27-28), 3919-3935.

High-resolution record of last post-glacial variations of sea-ice cover and river discharge in the western Laptev Sea (Arctic Ocean)

NASA Astrophysics Data System (ADS)

Stein, R. H.; Hörner, T.; Fahl, K.

2014-12-01

Here, we provide a high-resolution reconstruction of sea-ice cover variations in the western Laptev Sea, a crucial area in terms of sea-ice production in the Arctic Ocean and a region characterized by huge river discharge. Furthermore, the shallow Laptev Sea was strongly influenced by the post-glacial sea-level rise that should also be reflected in the sedimentary records. The sea Ice Proxy IP25 (Highly-branched mono-isoprenoid produced by sea-ice algae; Belt et al., 2007) was measured in two sediment cores from the western Laptev Sea (PS51/154, PS51/159) that offer a high-resolution composite record over the last 18 ka. In addition, sterols are applied as indicator for marine productivity (brassicasterol, dinosterol) and input of terrigenous organic matter by river discharge into the ocean (campesterol, ß-sitosterol). The sea-ice cover varies distinctly during the whole time period and shows a general increase in the Late Holocene. A maximum in IP25 concentration can be found during the Younger Dryas. This sharp increase can be observed in the whole circumarctic realm (Chukchi Sea, Bering Sea, Fram Strait and Laptev Sea). Interestingly, there is no correlation between elevated numbers of ice-rafted debris (IRD) interpreted as local ice-cap expansions (Taldenkova et al. 2010), and sea ice cover distribution. The transgression and flooding of the shelf sea that occurred over the last 16 ka in this region, is reflected by decreasing terrigenous (riverine) input, reflected in the strong decrease in sterol (ß-sitosterol and campesterol) concentrations. ReferencesBelt, S.T., Massé, G., Rowland, S.J., Poulin, M., Michel, C., LeBlanc, B., 2007. A novel chemical fossil of palaeo sea ice: IP25. Organic Geochemistry 38 (1), 16e27. Taldenkova, E., Bauch, H.A., Gottschalk, J., Nikolaev, S., Rostovtseva, Yu., Pogodina, I., Ya, Ovsepyan, Kandiano, E., 2010. History of ice-rafting and water mass evolution at the northern Siberian continental margin (Laptev Sea) during Late Glacial and Holocene times. Quaternary Science Reviews 29 (27-28), 3919-3935.

Stability of the Early Mars Atmosphere to Collapse into Permanent Polarcaps

NASA Technical Reports Server (NTRS)

Haberle, R. M.; Kahre, M. A.; Wordsworth, R.; Forget, F.

2016-01-01

The presence of a permanent CO2 polar ice cap on Mars has important consequences for the planet's climate system. The heat balance of such a cap, which is determined mainly by atmospheric heat transport, and the downward solar in infrared radiative fluxes, determines its surface temperature, which through the vapor pressure relation sets the mean annual surface pressure. On Mars today, for example, the south residual CO2 cap is present year-round with a mean annual temperature of approximately 145 K which corresponds to a mean annual CO2 vapor pressure of approximately 600 Pa. On early Mars, permanent polar caps are also possible especially since the sun was less luminous 3.5-4.0 Gya. Thus, the existence of permanent polar caps on early Mars is central to understanding the nature of the planets climate system in those ancient times and whether or not the atmosphere might have been capable of sustaining conditions suitable for liquid water flowing over the surface as is indicated in the geological record. Forget et al [1] showed that for present orbital properties atmospheric collapse into permanent polar caps could only be prevented for surface pressures roughly between 500 - 3000 hPa. Though follow-on studies confirm and extend the Forget et al. results [2], the full sensitivity of this "window" of stability has not been explored. There are many factors to consider such the albedo of the caps, dust content of the atmosphere, and the presence of water ice clouds. However, we begin our exploration of the stability of the early Martian atmosphere by focusing on the role of CO2 ice clouds. In some preliminary simulations with the Ames Mars General Circulation Model (GCM) we found that atmospheric collapse depends on assumptions regarding the fate of CO2 ice clouds. If, for example, we assume the clouds immediately fall to the surface, then in some cases collapse is favored. On the other hand if the clouds are allowed to fall and evaporate, collapse can be averted. This implies that CO2 ice cloud microphysics is important to the overall stability of the atmosphere. Though the Ames GCM has a sophisticated CO2 cloud microphysics package that includes nucleation, growth, and sedimentation (see accompanying poster by Kahre et al. [3]), we have implemented a simpler scheme based on the Forget et al. [1] approach to CO2 ice clouds. Our goal is to reproduce and expand their study. The key parameter in this approach is the concentration and vertical distribution of cloud condensation nuclei (CCN), i.e., dust particles. Fewer CCN lead to larger particles which fall faster, while higher CCN concentrations lead to smaller particles and thicker clouds that remain suspended for longer periods of time. We plan to explore the stability of the atmosphere to CCN concentrations and distributions and then assess the capability of thick early atmospheres to loft and distribute dust particles (CCN) around the planet. Thus, our work will shed light on the nature of the coupling between the dust and CO2 cycles and the implications it has for the early Mars climate system.

Microshear in the deep EDML ice core analyzed using cryogenic EBSD

NASA Astrophysics Data System (ADS)

Kuiper, Ernst-Jan; Pennock, Gill; Drury, Martyn; Kipfstuhl, Sepp; Faria, Sérgio; Weikusat, Ilka

2017-04-01

Ice sheets play an important role in sea level evolution by storing large amounts of fresh water on land. The ice in an ice sheet flows from the interior of the ice sheet to the edges where it either melts or calves into the ocean. This flow of ice results from internal deformation of the ice aggregate. Dislocation creep is assumed to be the dominant deformation mechanism for polar ice and is grain size insensitive. Recently, a different deformation mechanism was identified in the deeper part of the EDML ice core (Antarctica) where, at a depth of 2385 meters, the grain size strongly decreases, the grain aspect ratio increase and, the inclination of the grain elongation changes (Faria et al., 2006; Weikusat et al., 2017). At this depth the borehole displacement increases strongly (Weikusat et al., 2017), which indicates a relatively high strain rate. Part of this EDML ice core section was studied using cryogenic electron backscattered diffraction (cryo-EBSD) (Weikusat et al, 2011). EBSD produces high resolution, full crystallographic (a-axis and c-axis) maps of the ice core samples. EBSD samples were taken from an ice core section at 2392.2 meter depth. This section was chosen for its very small grain size and the strongly aligned grain boundaries. The EBSD maps show a very low orientation gradient of <0.3° per millimetre inside the grains, which is 5-10 times lower than the orientation gradients found in other parts of the ice core. Furthermore, close to some grain boundaries, a relatively strong orientation gradient of 1°-2° per millimetre was found. The subgrain boundaries developed such that they elongate the sliding boundaries in order to accommodate the incompatibilities and maintain the strongly aligned grain boundary network. We identify the dominant deformation mechanism in this part of the ice core as grain boundary sliding accommodated by localized dislocation creep, which is a process similar to microshear (Drury and Humpreys, 1988). The existence of layers of soft ice has serious implications for ice core dating, related paleoclimate studies and ice flow modelling with respect to ice sheet mass balance and sea level predictions. References: - Drury and Humphreys, 1988. Microstructural shear criteria associated with grain boundary sliding during ductile deformation. J. of Struc. Geol. 10, 1, 83-89. - Faria et al., 2006. Is Antarctica like a birthday cake?, Max Planck Institute of Mathematics and the Sciences - Weikusat et al., 2011. Cryogenic EBSD on ice: preserving a stable surface in a low pressure SEM. J. Micros. 242, 3, 295-310. (doi: 10.1111/j.1365-2818.2010.03471.x) - Weikusat et al., 2017. Physical analysis of an Antarctic ice core-towards an integration of micro- and macrodynamics of polar ice. Phil. Trans. R. Soc. A 375, 2015347. (doi:10.1098/rsta.2015.0347)

Snow contribution to first-year and second-year Arctic sea ice mass balance north of Svalbard

NASA Astrophysics Data System (ADS)

Granskog, Mats A.; Rösel, Anja; Dodd, Paul A.; Divine, Dmitry; Gerland, Sebastian; Martma, Tõnu; Leng, Melanie J.

2017-03-01

The salinity and water oxygen isotope composition (δ18O) of 29 first-year (FYI) and second-year (SYI) Arctic sea ice cores (total length 32.0 m) from the drifting ice pack north of Svalbard were examined to quantify the contribution of snow to sea ice mass. Five cores (total length 6.4 m) were analyzed for their structural composition, showing variable contribution of 10-30% by granular ice. In these cores, snow had been entrained in 6-28% of the total ice thickness. We found evidence of snow contribution in about three quarters of the sea ice cores, when surface granular layers had very low δ18O values. Snow contributed 7.5-9.7% to sea ice mass balance on average (including also cores with no snow) based on δ18O mass balance calculations. In SYI cores, snow fraction by mass (12.7-16.3%) was much higher than in FYI cores (3.3-4.4%), while the bulk salinity of FYI (4.9) was distinctively higher than for SYI (2.7). We conclude that oxygen isotopes and salinity profiles can give information on the age of the ice and enables distinction between FYI and SYI (or older) ice in the area north of Svalbard.