Antarctica (Glaciology) Research Papers - Academia.edu (original) (raw)

This paper, the last of four papers on Atlantis – Discovery, Sinking, Marduk and Destruction – examines the extent of the tsunami of 9,577 BC. It compares calculated flood levels with actual flood levels in Europe, Morocco, and the... more

This paper, the last of four papers on Atlantis – Discovery, Sinking, Marduk and Destruction – examines the extent of the tsunami of 9,577 BC. It compares calculated flood levels with actual flood levels in Europe, Morocco, and the Americas. It explains significant extinctions in Britain and France. The analysis encountered two previous tsunamis, one in 10,392 BC from the Arctic Ocean, the second off the coast of South Carolina above the Blake Escarpment around 14,000 BC. It found the trigger for the Atlantis tsunami was a rogue planet called Marduk-Nibiru-Storm. In addition to sinking Atlantis, satellites of Marduk ablated all the ice off the north half of Antarctica.

The careful study of the legal status of ice in public international law is often a difficult exercise in that it is first necessary to consider the classification and categorization of ice. As glaciologists and all polar experts know,... more

The careful study of the legal status of ice in public international law is often a difficult exercise in that it is first necessary to consider the classification and categorization of ice. As glaciologists and all polar experts know, there is no single type of ice. They can be very different in nature, origin or physical properties.

Recently NATURE published a discussion on construction of sills in attempt to prevent or slow melting glaciers that are discharging ice into the ice fjords. Several further papers promptly followed publication of this essentially... more

Recently NATURE published a discussion on construction of sills in attempt to prevent or slow melting glaciers that are discharging ice into the ice fjords. Several further papers promptly followed publication of this essentially erroneous article in a respected NATURE magazine. Here it is pointed out that there is a discrepancy of several magnitudes thus excluding a long-term viability to manage the edges of ice fjords or continental ice shelves/sheets due to a phenomenon known as the mega-erratics. These are blocks of hard rocks that are several kilometres in size that have been dislocated by a warmed and wet edges of glacier/ice sheet/ice shelf. This Parliament evidence points out the error that was not apparent to the peer-reviewers at the time and in subsequent papers that followed. The Parliament was shown evidence that large enough obstacles cannot be possibly made to prevent ice discharges due to a progression of melting, that softens and lubricates glaciers, ice caps and ice sheets. The forces unleashed by the ice front exceeds several magnitudes from the conceived objects that sills were proposed. The only, and very only effect is temporary and limited to prevention of warm water incursion where these methods will work for a while in a cold, dry, and relatively stable ice formations. A long-term projections suggested to prevent warmed and water-infested glaciers from discharging ice into the ocean cannot be made as the forces of ice exceed many magnitudes of the sills and levies that can be made of concrete blocks, aggregates or other materials. Thus the prevention of sea level rise by this method for centuries or millennia is not functional one and thus the mitigation and prevention of rubbish gyros in ocean, the supply of housing, nuclear and food production security must be looked at as solution by the ocean littoral states. Several examples of various types of risk to the sustainability of oceans have been presented in addition to the above exposed misconception. This comes with much regret as it appears that one 'hoped-for-solution' to manage the future climate change impacts has largely foundered on the issue that the sills cannot be made strong enough to contain most important, warmed glaciers or edges of unstable ice shelves. However, for a short-term this may offer small-scale solutions provided that costs remain sufficiently small. Aggressively melting ice formations with darkened surfaces, wide spread melt water ponds, or water filled crevasses it does not offer much, if any, prolonged ice stability. (The document is best viewed as a .pdf file due to the lay-out of graph and legends.)

This study presents the first high-resolution orthophoto maps and digital surface models (DSMs) of the largest Argentine Islands, West Antarctica. Aerial surveys with small unmanned aerial vehicle (UAV) were performed in Austral summer,... more

This study presents the first high-resolution orthophoto maps and digital surface models (DSMs) of the largest Argentine Islands, West Antarctica. Aerial surveys with small unmanned aerial vehicle (UAV) were performed in Austral summer, 2018, taking 10,041 aerial photographs. Accuracy requirements were ensured using ground control points (GCPs). A resolution of 3.4 and 6.8 cm/px of orthomosaics and DSMs is reached on average, and the RMS reproduction error is 0.22 m on average. We report the morphometric parameters of surveyed islands and discuss issues related to accuracy and the usage of UAVs in polar conditions. This study demonstrates that small and low cost UAVs can be successfully used in harsh polar conditions to obtain accurate orthomosaics and DSMs of mainly glaciated terrain. We provide all generated materials in full resolution available in a scientific data repository that could be used for the monitoring of ice cap changes, vegetation cover, and wildlife populations.

An important share of paleoclimatic information is buried within the lowermost layers of deep ice cores. Because improving our records further back in time is one of the main challenges in the near future, it is essential to judge how... more

An important share of paleoclimatic information is buried within the lowermost layers of deep ice cores. Because improving our records further back in time is one of the main challenges in the near future, it is essential to judge how deep these records remain unaltered, since the proximity of the bedrock is likely to interfere both with the recorded temporal sequence and the ice properties. In this paper, we present a multiparametric study (δD-δ18Oice, δ18Oatm, total air content, CO2, CH4, N2O, dust, high-resolution chemistry, ice texture) of the bottom 60 m of the EPICA (European Project for Ice Coring in Antarctica) Dome C ice core from central Antarctica. These bottom layers were subdivided into two distinct facies: the lower 12 m showing visible solid inclusions (basal dispersed ice facies) and the upper 48 m, which we will refer to as the "basal clean ice facies". Some of the data are consistent with a pristine paleoclimatic signal, others show clear anomalies. It is demonstrated that neither large-scale bottom refreezing of subglacial water, nor mixing (be it internal or with a local basal end term from a previous/initial ice sheet configuration) can explain the observed bottom-ice properties. We focus on the high-resolution chemical profiles and on the available remote sensing data on the subglacial topography of the site to propose a mechanism by which relative stretching of the bottom-ice sheet layers is made possible, due to the progressively confining effect of subglacial valley sides. This stress field change, combined with bottom-ice temperature close to the pressure melting point, induces accelerated migration recrystallization, which results in spatial chemical sorting of the impurities, depending on their state (dissolved vs. solid) and if they are involved or not in salt formation. This chemical sorting effect is responsible for the progressive build-up of the visible solid aggregates that therefore mainly originate "from within", and not from incorporation processes of debris from the ice sheet's substrate. We further discuss how the proposed mechanism is compatible with the other ice properties described. We conclude that the paleoclimatic signal is only marginally affected in terms of global ice properties at the bottom of EPICA Dome C, but that the timescale was considerably distorted by mechanical stretching of MIS20 due to the increasing influence of the subglacial topography, a process that might have started well above the bottom ice. A clear paleoclimatic signal can therefore not be inferred from the deeper part of the EPICA Dome C ice core. Our work suggests that the existence of a flat monotonic ice–bedrock interface, extending for several times the ice thickness, would be a crucial factor in choosing a future "oldest ice" drilling location in Antarctica.

The South Shetland Islands are located at the northern tip of the Antarctic Peninsula (AP) which is among the fastest warming regions on Earth. Surface air temperature increases (~3 K in 50 years) are concurrent with retreating glacier... more

The South Shetland Islands are located at the northern tip of the Antarctic Peninsula (AP) which is among the fastest warming regions on Earth. Surface air temperature increases (~3 K in 50 years) are concurrent with retreating glacier fronts, an increase in melt areas, ice surface lowering and rapid break-up and disintegration of ice shelves. We have compiled a unique meteorological dataset for the King George Island (KGI)/Isla 25 de Mayo, the largest of the South Shetland Islands. It comprises high-temporal resolution and spatially distributed observations of surface air temperature, wind directions and wind velocities, glacier ice temperatures in profile with a fully equipped automatic weather station as well as snow accumulation and ablation measurements on the Warszawa Icefield, since November 2010 and ongoing. In combination with long-term synoptic datasets (40 and 10 years, respectively) and atmospheric circulation indices datasets, we have looked at changes in the climatological drivers of the glacial melt processes, and the sensitivity of the inland ice cap with regard to winter melting periods and pressure anomalies. The analysis has revealed a positive trend of 5 K over four decades in minimum surface air temperatures for winter months, clearly exceeding the published annual mean statistics, associated to a negative trend in mean monthly winter sea level pressure. This concurs with a positive trend in the Southern Annular Mode (SAM) index, which gives a measure for the strength and extension of the Antarctic vortex. We connect this trend with a higher frequency of low-pressure systems hitting the South Shetland Islands during austral winter, bringing warm and moist air masses from lower latitudes. A revision of spatial and seasonal changes in adiabatic air temperature lapse rates reveals the high sensitivity of the upper ice cap to free atmospheric flow and synoptic changes. Observed surface air temperature lapse rates show a high variability during winter months (standard deviations up to ±1.0 K/100 m), and a distinct spatial variability reflecting the impact of synoptic weather patterns especially during winter glacial mass accumulation periods. The increased mesocyclonic activity during the winter time in the study area results in intensified advection of warm, moist air with high temperatures and rain, and leads to melt conditions on the ice cap, fixating surface air temperatures to the melting point. This paper assesses the impact of long-term change in large-scale atmospheric circulation and variability and climatic changes on the atmospheric surface layer and glacier mass accumulation of the upper ice cap during winter season for the Warszawa Icefield on KGI. Supplementary data are available at http://dx.doi.org/10.1594/PANGAEA.848704.
Zusammenfassung: Die Südshetland-Inseln befinden sich an der nördlichen Spitze der Antarktischen Halbinsel, welche weltweit zu den Regionen zählt, die am stärksten von der globalen Erwärmung betroffen sind. Beträchtliche Änderungen in der Umwelt sind die Konsequenz dieser Erwärmung. Außergewöhnliche Änderungsraten in der bodennahen Lufttem-peratur (~3 K in 50 Jahren) gehen einher mit dem Rückzug von Gletscherfronten, der Zunahme von Gletscherschmelze, einem Absenken der Eisoberflächen und der Desintegration von Eisschelfen. Wir haben für die King George Insel/Isla 25 de Mayo (KGI), der größten der Südshetland Inseln, einen einzigartigen Datensatz zusammen getragen. Dieser beinhaltet zeitlich hochaufgelöste und räumliche Messungen von oberflächennaher Lufttemperatur, Windrichtungen und-geschwin-digkeiten, Profile von Eistemperaturen mit einer voll ausgestatteten automatischen Wetterstation sowie Messungen von Schnee Akkumulation und Ablation auf dem Warschauer Eisfeld von November 2010 an und andauernd. In Verbindung mit langzeitlichen synoptischen Datensätzen (40 Jahre von 6-stündlichen Messungen) und Datensätzen von atmosphä-rischen Zirkulations-Indizes, untersuchen wir die klimatologischen Treiber für die Gletscherschmelze-Prozesse und die Vulnerabilität des Inland-Eisschildes mit Schwerpunkt auf den winterlichen Schmelzperioden und Luftdruck-Anomalien. Die Analyse zeigt einen positiven Trend von 5 K über 4 Dekaden in den Tagesminima der Lufttemperatur für die Wintermo-nate, welche die publizierten Trends der annualen Mittelwerte klar übersteigt, in Verbindung mit einem negativen Trend im monatlichen Mittel des barometrischen Luftdrucks auf Meeresniveau. Diese Änderungen gehen einher mit einem positiven Trend des Southern Annular Mode (SAM) Index, welcher ein Maß für die Stärke und die Ausdehnung des Antarktischen Vortex ist. Wir verbinden diese Beobachtungen mit einer höheren Frequenz von Tiefdruckgebieten, die im Süd-Winter auf die Südshetland-Inseln treffen und warme, feuchte Luftmassen aus den niedrigeren Breiten bringen. Durch seine Exposition ist die Eiskappe von KGI besonders empfindlich gegenüber Änderungen in der winterlichen Akkumulationsperiode von Gletschermassen. Eine Überprüfung der saisonalen und räumlichen Variabilität der Lufttemperaturgradienten zeigen 342 Vol. 69 · No. 4 eine höhere Sensitivität des oberen Gletschers gegenüber Zirkulation der freien Atmosphäre und synoptischen Einflüssen insbesondere während der winterlichen Akkumulationsperiode von Gletschermassen. Oberflächennahe Lufttemperaturgra-dienten zeigen eine hohe Streuung in Wintermonaten (Standardabweichungen bis zu ±1.0 K/100 m) und eine ausgeprägte räumliche Variabilität, welche den Einfluss der synoptischen Wetterphänomene widerspiegelt. Die verstärkte zyklonische Aktivität im Forschungsgebiet in der Winterzeit resultiert in der Advektion feuchter, warmer Luft mit Regen und erhöhten Temperaturen in die Region, so dass sich regelmäßig winterliche Phasen mit Schmelzbedingungen einstellen. In dieser Pu-blikation untersuchen wir den Einfluss von großskaligen und klimatischen Änderungen auf die bodennahe atmosphärische Grenzschicht und in Gletschermassen-Akkumulation des höher gelegenen Eisschildes während der Wintermonate. Die hier publizierten Daten sind verfügbar unter http://dx.doi.org/10.1594/PANGAEA.848704.

We present spatiotemporal mass balance trends for the Antarctic Ice Sheet from a statistical inversion of satellite altimetry, gravimetry, and elastic-corrected GPS data for the period 2003–2013. Our method simultaneously determines... more

We present spatiotemporal mass balance trends for the Antarctic Ice Sheet from a statistical inversion of satellite altimetry, gravimetry, and elastic-corrected GPS data for the period 2003–2013. Our method simultaneously determines annual trends in ice dynamics, surface mass balance anomalies, and a time-invariant solution for glacio-isostatic adjustment while remaining largely independent of forward models. We establish that over the period 2003–2013, Antarctica has been losing mass at a rate of −84 ± 22 Gt yr −1 , with a sustained negative mean trend of dynamic imbalance of −111 ± 13 Gt yr −1. West Antarctica is the largest contributor with −112 ± 10 Gt yr −1 , mainly triggered by high thinning rates of glaciers draining into the Amundsen Sea Embayment. The Antarctic Peninsula has experienced a dramatic increase in mass loss in the last decade, with a mean rate of −28 ± 7 Gt yr −1 and significantly higher values for the most recent years following the destabilization of the Southern Antarctic Peninsula around 2010. The total mass loss is partly compensated by a significant mass gain of 56 ± 18 Gt yr −1 in East Antarctica due to a positive trend of surface mass balance anomalies.

Within the context of the post-Cold War period, rising power states have developed new regional and global interests, including with respect to Antarctica. In this paper, we analyse the role of Antarctica within Brazil’s rising power... more

Within the context of the post-Cold War period, rising power states have developed new regional and global interests, including with respect to Antarctica. In this paper, we analyse the role of Antarctica within Brazil’s rising power strategy, defined in terms of the foreign policy, defence strategy, and science and technology goals promoted by its policy elites. Focusing on the past decade, we find that Antarctica has gained greater visibility in all three aspects of Brazil’s rising power strategy. Regionally, Antarctica has become an important element within Brazil’s new defence policy for the South Atlantic region, as well as a way for Brazil to enhance cooperation with other South American states. In terms of its global ambitions, becoming a more active player within the Antarctic Treaty System is seen as a way for Brazil to participate more directly in debates with global reach. Finally, Antarctic research is viewed as a promising component of Brazil’s efforts to boost its science and technology capacity, and therefore its socio-economic development and competitiveness. In attaining these goals, Brazil faces a number of hurdles that became more evident after a 2012 fire destroyed most of its Antarctic base, although reconstruction efforts have produced new dynamics of cooperation, domestically and internationally.

The work aims to investigate the geomorphological and sedimentological aspects of Union Glacier area (79°45'00''S; 82°30'00''W), southern sector of Ellsworth Mountains. Geomorphological cartography based on 15 m ASTER (2010) satellite... more

The work aims to investigate the geomorphological and sedimentological aspects of Union Glacier area (79°45'00''S; 82°30'00''W), southern sector of Ellsworth Mountains. Geomorphological cartography based on 15 m ASTER (2010) satellite imagery and fi eld works were carried out during the Brazilian expedition (2011/2012) enabled the identifi cation of morainic formations: ice-cored hummock moraines, supraglacial moraines, and recession moraines in the interior of the valleys. With the exception of the latter one, all types of moraines have been developed on the blue-ice areas. The evidence for paleo wet-based glacial conditions is reconstructed from a range of geomorphological record, including exposed abrasion marks, striations and glaciotectonic deformation. This type of deformation is represented by lee sides of oversteep ening bedrock promontories which follow the tributaries of glaciers ice fl ow. Glacial sediments were collected from the moraines for granulometric and morphometric analyses. They show the prevalence of sandy gravel and sand texture, low quantity of fi ne fractions, and absence of attributes such as striated and faceted clasts, which indicate, on the other side, low-sediment transport capacity from the ice sheet bottom. It is inferred that the moraine debris are originated from local sources. Weathering action and constant katabatic winds are possibly the major agents of transport and alteration of the exposed sediments. The geomorphological features

We describe a geophysical technique to measure englacial vertical velocities through to the beds of ice sheets without the need for borehole drilling. Using a ground-based phase-sensitive radio echo sounder (pRES) during seven Antarctic... more

We describe a geophysical technique to measure englacial vertical velocities through to the
beds of ice sheets without the need for borehole drilling. Using a ground-based phase-sensitive radio echo
sounder (pRES) during seven Antarctic field seasons, we measure the temporal changes in the position of
englacial reflectors within ice divides up to 900 m thick on Berkner Island, Roosevelt Island, Fletcher
Promontory, and Adelaide Island. Recorded changes in reflector positions yield “full-depth” profiles of vertical
ice velocity that we use to examine spatial variations in ice flow near the divides. We interpret these variations
by comparing them to the results of a full-Stokes simulation of ice divide flow, qualitatively validating the
model and demonstrating that we are directly detecting an ice-dynamical phenomenon called the Raymond
Effect. Using pRES, englacial vertical ice velocities can be measured in higher spatial resolution than is
possible using instruments installed within the ice. We discuss how these measurements could be used with
inverse methods to measure ice rheology and to improve ice core dating by incorporating pRES-measured
vertical velocities into age modeling.

We present spatiotemporal mass balance trends for the Antarctic Ice Sheet from a statistical inversion of satellite altimetry, gravimetry, and elastic-corrected GPS data for the period 2003–2013. Our method simultaneously determines... more

We present spatiotemporal mass balance trends for the Antarctic Ice Sheet from a statistical inversion of satellite altimetry, gravimetry, and elastic-corrected GPS data for the period 2003–2013. Our method simultaneously determines annual trends in ice dynamics, surface mass balance anomalies, and a time-invariant solution for glacio-isostatic adjustment while remaining largely independent of forward models. We establish that over the period 2003–2013, Antarctica has been losing mass at a rate of −84 ± 22 Gt yr −1 , with a sustained negative mean trend of dynamic imbalance of −111 ± 13 Gt yr −1. West Antarctica is the largest contributor with −112 ± 10 Gt yr −1 , mainly triggered by high thinning rates of glaciers draining into the Amundsen Sea Embayment. The Antarctic Peninsula has experienced a dramatic increase in mass loss in the last decade, with a mean rate of −28 ± 7 Gt yr −1 and significantly higher values for the most recent years following the destabilization of the Southern Antarctic Peninsula around 2010. The total mass loss is partly compensated by a significant mass gain of 56 ± 18 Gt yr −1 in East Antarctica due to a positive trend of surface mass balance anomalies.

In glacial environments particle-size analysis of moraines provides insights into clast origin, transport history, depositional mechanism and processes of reworking. Traditional methods for grain-size classification are labour-intensive,... more

In glacial environments particle-size analysis of moraines provides insights into clast origin, transport history, depositional mechanism and processes of reworking. Traditional methods for grain-size classification are labour-intensive, physically intrusive and are limited to patch-scale (1m2) observation. We develop emerging, high-resolution ground- and unmanned aerial vehicle-based ‘Structure-from-Motion’ (UAV-SfM) photogrammetry to recover grain-size information across a moraine surface in the Heritage Range, Antarctica. SfM data products were benchmarked against
equivalent datasets acquired using terrestrial laser scanning, and were found to be accurate to within
1.7 and 50mm for patch- and site-scale modelling, respectively. Grain-size distributions were obtained through digital grain classification, or ‘photo-sieving’, of patch-scale SfM orthoimagery. Photo-sieved distributions were accurate to <2mm compared to control distributions derived from dry-sieving. A relationship between patch-scale median grain size and the standard deviation of local surface elevations was applied to a site-scale UAV-SfM model to facilitate upscaling and the production of a spatially continuous map of the median grain size across a 0.3 km2 area of moraine. This highly automated workflow for site-scale sedimentological characterization eliminates much of the subjectivity associated with traditional methods and forms a sound basis for subsequent glaciological
process interpretation and analysis.

Marine ice accretes at the base of ice shelves, often infilling open structural weaknesses and increasing ice-shelf stability. However, the timing and location of marine ice formation remain poorly understood. This study determines marine... more

Marine ice accretes at the base of ice shelves, often infilling open structural weaknesses
and increasing ice-shelf stability. However, the timing and location of marine ice formation remain
poorly understood. This study determines marine ice source water composition and origin by examining
marine ice crystal morphology, water isotope and solute chemistry in ice samples collected from the
southern McMurdo Ice Shelf (SMIS), Antarctica. The measured co-isotopic record together with the
output of a freezing model for frazil crystals indicate a spatio-temporally varying water source of sea
water and relatively fresher water, such as melted meteoric or marine ice. This is in agreement with the
occurrence of primarily banded and granular ice crystal facies typical for frazil ice crystals that
nucleate in a supercooled mixture of water masses. We propose that marine ice exposed at the surface
of SMIS, which experiences summer melt, is routed to the ice-shelf base via the tide crack. Here frazil
crystals nucleate in a double diffusion mechanism of heat and salt between two water masses at their
salinity-dependent freezing point. Recycling of previously formed marine ice facilitates ice-shelf selfsustenance
in a warming climate.

We evaluate the performance of the low-cost seismic sensor Raspberry Shake (RS) to identify and monitor icequakes (which occur when glacial ice experiences brittle deformation) in extreme environments. In January 2020, three RS3D sensors... more

We evaluate the performance of the low-cost seismic sensor Raspberry Shake (RS) to identify and monitor icequakes (which occur when glacial ice experiences brittle deformation) in extreme environments. In January 2020, three RS3D sensors were installed on a katabatic wind-scoured blue ice area (BIA) close to the Princess Elisabeth Antarctica research station in Dronning Maud Land, East Antarctica. The sensors were configured for Antarctic deployment and placed in insulated enclosures to protect them from harsh weather systems. The RS network (installed in a triangular array) performed well in the cold and with rapid air temperature change, as diurnal temperatures fluctuated from a high of 0.0°C to a minimum temperature of −15.0°C. Although battery connectivity issues in one unit limit full triangulation of seismic signals, and high background noise may mask some seismic signals, data from the RS2 unit reveals that 2936 icequakes were detected over a 10-day period. The temporal occur...

We present a method for inferring time-dependent three-component surface deformation fields given a set of geodetic images of displacements collected from multiple viewing geome-tries. Displacements are parameterized in time with a... more

We present a method for inferring time-dependent three-component surface deformation fields given a set of geodetic images of displacements collected from multiple viewing geome-tries. Displacements are parameterized in time with a dictionary of displacement functions. The algorithm extends an earlier single-component (i.e., single line of sight) framework for time-series analysis to three spatial dimensions using combinations of multitemporal, multigeometry interferometic synthetic aperture radar (InSAR) and/or pixel offset (PO) maps. We demonstrate this method with a set of 101 pairs of azimuth and range PO maps generated for a portion of the Rutford Ice Stream, West Antarctica, derived from data collected by the COSMO-SkyMed satellite constellation. We compare our results with previously published InSAR mean velocity fields and selected GPS time series and show that our resulting three-component surface displacements resolve both secular motion and tidal variability. Index Terms— 3-D analysis, ocean tides, pixel offsets (POs), Rutford ice stream (RIS), synthetic aperture radar (SAR), time-series analysis.

Antarctica is the world's largest fresh-water reservoir, with the potential to raise sea levels by about 60 m. An ice sheet contributes to sea-level rise (SLR) when its rate of ice discharge and/or surface melting exceeds accumulation... more

Antarctica is the world's largest fresh-water reservoir, with the potential to raise sea levels by about 60 m. An ice sheet contributes to sea-level rise (SLR) when its rate of ice discharge and/or surface melting exceeds accumulation through snowfall. Constraining the contribution of the ice sheets to present-day SLR is vital both for coastal development and planning, and climate projections. Information on various ice sheet processes is available from several remote sensing data sets, as well as in situ data such as global positioning system data. These data have differing coverage, spatial support, temporal sampling and sensing characteristics, and thus, it is advantageous to combine them all in a single framework for estimation of the SLR contribution and the assessment of processes controlling mass exchange with the ocean. In this paper, we predict the rate of height change due to salient geophysical processes in Antarctica and use these to provide estimates of SLR contribu...

Data from the NASA GRACE satellite program show that the ice sheets in Greenland and Antarctica have undergone a steady decline in mass during 2002-2014, the entire period for which GRACE data are available as of this writing. Although... more

Data from the NASA GRACE satellite program show that the ice sheets in Greenland and Antarctica have undergone a steady decline in mass during 2002-2014, the entire period for which GRACE data are available as of this writing. Although the reasons for the decline are unclear, it is generally assumed that surface temperature is a factor in the observed mass loss in both ice sheets. Using detrended correlation analysis we find that mass loss from the Greenland ice sheet shows a statistically significant positive correlation consistent with the surface temperature hypothesis. No such correlation exists for ice sheet mass loss in Antarctica. We conclude that the two polar ice sheet mass loss trends are symptoms of very different underlying phenomena and they are therefore not directly comparable in terms of global warming and climate change.

Se analizan las implicancias del cambio climático para la Antártica.

S U M M A R Y In Antarctica, locally grounded ice, such as ice rises bordering floating ice shelves, plays a major role in the ice mass balance as it stabilizes the ice sheet flow from the hinterland. When in direct contact with the... more

S U M M A R Y In Antarctica, locally grounded ice, such as ice rises bordering floating ice shelves, plays a major role in the ice mass balance as it stabilizes the ice sheet flow from the hinterland. When in direct contact with the ocean, the ice rise buttressing effect may be altered in response of changing ocean forcing. To investigate this vulnerable zone, four sites near the boundary of an ice shelf with an ice rise promontory in Dronning Maud Land, East-Antarctica were monitored for a month in early 2014 with new instruments that include both seismic and GPS sensors. Our study indicated that this transition zone experiences periodic seismic activity resulting from surface crevassing during oceanic tide-induced flexure of the ice shelf. The most significant finding is the observation of apparent fortnightly tide-modulated low-frequency, long-duration seismic events at the seaward front of the ice rise promontory. A basal origin of these events is postulated with the ocean water surge at each new spring tide triggering basal crevassing or basal slip on a local bedrock asperity. Detection and monitoring of such seismicity may help identifying ice rise zones vulnerable to intensified ocean forcing.

Our study characterizes glacial and interglacial deposition on two Antarctic margins in order to discriminate between regional and continent-wide early to middle Pliocene warm intervals that caused sea-ice reduction and continental ice... more

Our study characterizes glacial and interglacial deposition on two Antarctic margins in order to discriminate between regional and continent-wide early to middle Pliocene warm intervals that caused sea-ice reduction and continental ice sheet retreat. We use a multi-proxy (i.e., sediment facies and grain size, siliceous microfossils, biogenic opal, geochemical composition and clay mineralogy) approach to examine sediments recovered in drill holes from the West Antarctic Peninsula and the East Antarctic Prydz Bay margins, focusing on the climatic record between 4 and 3.5 Ma.
Warm conditions in both East and West Antarctica are recorded, which based on our age model correspond to periods of prolonged or extreme warmth correlated with isotopic stages Gi5, Gi1, MG11 and MG7. For the Gi5 interglacial our data corroborates the 60% Dictyocha percentage at 34.60 mbsf previously reported from Prydz Bay and interpreted to indicate a SSST of about 5.6 °C above present. Our higher-resolution sampling interval shows Dictyocha percentages up to 87.5%, suggesting even higher SSSTs above present levels. During MG11, which coincides with the section dated by the magnetic polarity reversal Gilbert-Gauss at 3.58 Ma, SSSTs were tentatively 2.5°–4° warmer than present, and reduced sea-ice cover in Prydz Bay and probably also west of the Antarctic Peninsula is indicated by increased primary productivity. In addition, a reduction of ice sheet size is suggested by the bioturbated and IRD-enriched facies that characterize these high- productivity intervals. Based in our age model and calculated sedimentation rates glacial–interglacial cyclicity between 4 and 3.5 Ma in the cores from Antarctic Peninsula and Prydz Bay Sites, result in frequencies consistent with obliquity and precession forcing.
The prolonged early-middle Pliocene warm period was superimposed on a cooling trend recorded by the: 1) increase of the terrigenous sediment supply at all our sites starting between 3.7 and 3.6 Ma, and 2) decrease in SSSTs (from >5.6 °C at 3.7 Ma to 4°–2.7 °C at 3.6 Ma, and 2.5 °C at 3.5 Ma.) indicated by the silicoflagellate W/C R from Site 1165. We postulate that, although the start of a cooling trend is recorded at about 3.7–3.6-Ma, relatively warm conditions prevailed until 3.5 Ma capable of maintained open marine conditions with reduced or no sea-ice and reduced ice sheet volume and extent.
The information in this paper regarding the timing of continental-wide and regional warm events and the paleoenvironmental conditions that characterized them (i.e., SSST, extent of sea ice, and ice sheet size) are relevant to help constrain paleoclimate and ice sheet models for the early-middle Pliocene, a time period when the level of warming according to the Intergovernmental Panel on Climate Change 2007 report, is within range of the estimates of the Earth's global temperature increases for the 21st century. These data, when linked to modeling studies like those of Pollard and DeConto (2009) will further our understanding of how these ice sheets may respond to future warming of the southern high latitudes.

Supraglacial lakes can drain to the bed of ice sheets, affecting ice dynamics, or over their surface, relocating surface water. Focusing on surface drainage, we first discuss observations of lake drainage. In particular, for the first... more

Supraglacial lakes can drain to the bed of ice sheets, affecting ice dynamics, or over their
surface, relocating surface water. Focusing on surface drainage, we first discuss observations of lake
drainage. In particular, for the first time, lakes are observed to drain >70 km across the Nivlisen ice
shelf, East Antarctica. Inspired by these observations, we develop a model of lake drainage through a
channel that incises into an ice-sheet surface by frictional heat dissipated in the flow. Modelled lake
drainage can be stable or unstable. During stable drainage, the rate of lake-level drawdown exceeds the
rate of channel incision, so discharge from the lake decreases with time; this can prevent the lake from
emptying completely. During unstable drainage, discharge grows unstably with time and always
empties the lake. Model lakes are more prone to drain unstably when the initial lake area, the lake input
and the channel slope are larger. These parameters will vary during atmospheric-warming-induced
ablation-area expansion, hence the mechanisms revealed by our analysis can influence the dynamic
response of ice sheets to warming through their impact on surface-water routing and storage.

Antarctica is the world’s largest fresh-water reservoir, with the potential to raise sea levels by about 60 m. An ice sheet contributes to sea-level rise (SLR) when its rate of ice discharge and/or surface melting exceeds accumulation... more

Antarctica is the world’s largest fresh-water reservoir, with the potential to raise sea levels by about 60 m. An ice sheet
contributes to sea-level rise (SLR) when its rate of ice discharge and/or surface melting exceeds accumulation through
snowfall. Constraining the contribution of the ice sheets to present-day SLR is vital both for coastal development and
planning, and climate projections. Information on various ice sheet processes is available from several remote sensing data
sets, as well as in situ data such as global positioning system data. These data have differing coverage, spatial support,
temporal sampling and sensing characteristics, and thus, it is advantageous to combine them all in a single framework for
estimation of the SLR contribution and the assessment of processes controlling mass exchange with the ocean.
In this paper, we predict the rate of height change due to salient geophysical processes in Antarctica and use these to
provide estimates of SLR contribution with associated uncertainties. We employ a multivariate spatio-temporal model,
approximated as a Gaussian Markov random field, to take advantage of differing spatio-temporal properties of the processes
to separate the causes of the observed change. The process parameters are estimated from geophysical models,
while the remaining parameters are estimated using a Markov chain Monte Carlo scheme, designed to operate in a high performance computing environment across multiple nodes. We validate our methods against a separate data set and
compare the results to those from studies that invariably employ numerical model outputs directly. We conclude that it is
possible, and insightful, to assess Antarctica’s contribution without explicit use of numerical models. Further, the results
obtained here can be used to test the geophysical numerical models for which in situ data are hard to obtain.