Ice Cap Area Research Articles

Improved estimates of glacier change rates at Nevado Coropuna Ice Cap, Peru

ABSTRACTAccurate quantification of rates of glacier mass loss is critical for managing water resources and for assessing hazards at ice-clad volcanoes, especially in arid regions like southern Peru. In these regions, glacier and snow melt are crucial dry season water resources. In order to verify previously reported rates of ice area decline at Nevado Coropuna in Peru, which are anomalously rapid for tropical glaciers, we measured changes in ice cap area using 259 Landsat images acquired from 1980 to 2014. We find that Coropuna Ice Cap is presently the most extensive ice mass in the tropics, with an area of 44.1 km2, and has been shrinking at an average area loss rate of 0.409 km2a−1(~0.71% a−1) since 1980. Our estimated rate of change is considerably lower than previous studies (1.4 km2a−1or ~2.43% a−1), but is consistent with other tropical regions, such as the Cordillera Blanca located ~850 km to the NW (~0.68% a−1). Thus, if glacier recession continues at its present rate, our results suggest that Coropuna Ice Cap will likely continue to contribute to water supply for agricultural and domestic uses until ~2120, which is nearly 100 years longer than previously predicted.

Glacier surface temperatures in the Canadian High Arctic, 2000–15

ABSTRACTCanada's Queen Elizabeth Islands (QEI) contain ~14% of the world's glacier and ice-cap area. Sparse in-situ measurements indicate that interannual variability in glacier surface mass balance in this region is driven primarily by variations in summer melt, and that the annual surface mass balance of four index glaciers has become increasingly negative since 2007. Here, we use a 16-a record of satellite-derived mean summer (June–August) land surface temperatures (LST) from NASA's Moderate Resolution Imaging Spectroradiometer to investigate large-scale spatial and temporal variability in the duration and intensity of summer melt across glaciated surfaces in the QEI from 2000 to 2015. During this period, QEI mean summer glacier surface temperatures increased at an average rate of 0.06 ± 0.04°C a−1, for a total of nearly 1°C. Most of this increase occurred between 2005 and 2012, when mean summer near-surface (2 m) and upper-air (700 hPa) temperatures were 1.0–1.2°C higher than the 1948–2015 mean. There is a strong correlation between the glacier LST and 700 hPa air temperature records (r> 0.8). The period 2005–12, when mean summer LSTs were anomalously high, was likely the warmest period in the region since at least 1948.

The extent of middle Pleistocene ice cap in the coastal Dinaric Mountains of Croatia

Solitary limestone blocks and groups of blocks occur on Risnjak and Velebit Mountains and on the northern Adriatic islands of Krk and Rab. Previous researchers have interpreted some of these as a) erratic blocks, b) corrosional remnants, or c) rockfalls. We have studied their mode of occurrence and composition, and revised previous interpretations of their origin in the light of transport mechanism and depositional processes. After analyzing the context of the block positions and the physical processes responsible for their emplacement, and taking into account their sedimentological context (their association with glaciogenic sediments), we herein propose a glacial origin for most of these blocks. However, some blocks are indeed shaped by sub-soil corrosion, as evidenced by their structure. The interpreted erratic blocks on the inner northern Adriatic Sea islands document the presence of middle Pleistocene glaciation of Dinaric Mountains though not its maximal extent, which is still unclear as the ice terminus was in the area that is inundated by postglacial rise of Adriatic Sea. The reconstructed ice cap area, which extended along the coastal mountains from Risnjak Mt. to south Velebit Mt. and across the range from Lika Polje to Rab Island, is conservatively estimated to be 5400 km2.

Surface velocity and mass balance of Livingston Island ice cap, Antarctica

Abstract. The mass budget of the ice caps surrounding the Antarctica Peninsula and, in particular, the partitioning of its main components are poorly known. Here we approximate frontal ablation (i.e. the sum of mass losses by calving and submarine melt) and surface mass balance of the ice cap of Livingston Island, the second largest island in the South Shetland Islands archipelago, and analyse variations in surface velocity for the period 2007–2011. Velocities are obtained from feature tracking using 25 PALSAR-1 images, and used in conjunction with estimates of glacier ice thicknesses inferred from principles of glacier dynamics and ground-penetrating radar observations to estimate frontal ablation rates by a flux-gate approach. Glacier-wide surface mass-balance rates are approximated from in situ observations on two glaciers of the ice cap. Within the limitations of the large uncertainties mostly due to unknown ice thicknesses at the flux gates, we find that frontal ablation (−509 ± 263 Mt yr−1, equivalent to −0.73 ± 0.38 m w.e. yr−1 over the ice cap area of 697 km2) and surface ablation (−0.73 ± 0.10 m w.e. yr−1) contribute similar shares to total ablation (−1.46 ± 0.39 m w.e. yr−1). Total mass change (δM = −0.67 &plusmn 0.40 m w.e. yr−1) is negative despite a slightly positive surface mass balance (0.06 ± 0.14 m w.e. yr−1). We find large interannual and, for some basins, pronounced seasonal variations in surface velocities at the flux gates, with higher velocities in summer than in winter. Associated variations in frontal ablation (of ~237 Mt yr−1; −0.34 m w.e. yr−1) highlight the importance of taking into account the seasonality in ice velocities when computing frontal ablation with a flux-gate approach.

Climate Inferences from a Glaciological Reconstruction of the Late Pleistocene Wind River Ice Cap, Wind River Range, Wyoming

We reconstructed the former ice cap of the Wind River Range, Wyoming, using a glaciological model with scaled modern temperature and precipitation inputs to examine probable climate during the local Last Glacial Maximum (LGM) (or Pinedale glaciation). A key result is that temperature anomalies of - 10 °C, -8.5 °C, -6.5 °C, and -5 °C must compensate respective precipitation values of 50%, 100%, 200%, and 300% that of modern in order for the maximum glacier system to attain equilibrium. In further sensitivity tests, we find that ice-cap area and volume shrink by 75% under a climate forcing 50% modern and 50% LGM. The glacier system disappears altogether in ∼100 years when subjected to sustained modern conditions. Our results are consistent with other interpretations of western U.S. LGM climate, and demonstrate that the Wind River Ice Cap could have disintegrated rapidly during the first phase of the termination. In future work we will simulate glacier-climate evolution as constrained by emerging 10Be moraine chronologies.

Extreme melt on Canada's Arctic ice caps in the 21st century

[1] Canada's Queen Elizabeth Islands contain ∼14% of Earth's glacier and ice cap area. Snow accumulation on these glaciers is low and varies little from year to year. Changes in their surface mass balance are driven largely by changes in summer air temperatures, surface melting and runoff. Relative to 2000–2004, strong summer warming since 2005 (1.1 to 1.6°C at 700 hPa) has increased summer mean ice surface temperatures and melt season length on the major ice caps in this region by 0.8 to 2.2°C and 4.7 to 11.9 d respectively. 30–48% of the total mass lost from 4 monitored glaciers since 1963 has occurred since 2005. The mean rate of mass loss from these 4 glaciers between 2005 and 2009 (−493 kg m−2 a−1) was nearly 5 times greater than the 1963–2004 average. In 2007 and 2008, it was 7 times greater (−698 kg m−2 a−1). These changes are associated with a summer atmospheric circulation configuration that favors strong heat advection into the Queen Elizabeth Islands from the northwest Atlantic, where sea surface temperatures have been anomalously high.

Forty-seven Years of Research on the Devon Island Ice Cap, Arctic Canada

The Devon Island ice cap has been the subject of scientific study for almost half a century, beginning with the first mass balance measurements in 1961. Research on the ice cap was the first to investigate (1) the role of meltwater in seasonal ice-velocity variations on a polythermal Arctic ice cap, (2) the use of air temperature rather than net radiation as a proxy for the energy driving surface melt, and (3) the influence of the changing frequency of specific synoptic weather configurations on glacier melt and mass balance. Other research has included investigations of ice cap geometry, flow dynamics, and mass balance; ice core analyses for records of past climate and contaminant deposition; and studies of changes in ice cap area and volume and their relationship to surface mass balance and ice dynamics. Current research includes ground studies connected to efforts to calibrate and validate the radar altimeter that will be carried by the European Space Agency’s (ESA) CryoSat2 satellite, and a major collaborative Canadian International Polar Year (IPY) project focused on the Belcher Glacier, on the northeast side of the ice cap, that examines hydrodynamics of large tidewater glaciers. This paper summarizes our current knowledge of the Devon Island ice cap and identifies some of the outstanding questions that continue to limit our understanding of climate-ice cap interactions in Arctic regions.

Increased aridity in the Mediterranean region under greenhouse gas forcing estimated from high resolution simulations with a regional climate model

We use three measures of aridity, the Köppen climate classification, the UNEP aridity index and the Budyko dryness index, to estimate the possible effects of late 21st century climate change on the Mediterranean region under increased greenhouse gas concentrations (A2 and B2 IPCC emission scenarios) as simulated with a high resolution (20 km grid interval) regional climate model (the ICTP RegCM). A basic validation of the reference simulation along with a brief discussion of the surface climate changes for the A2 and B2 scenarios is also provided. Analysis of the changes in all three aridity measures indicates that by the end of the 21st century the Mediterranean region might experience a substantial increase in the northward extension of dry and arid lands, particularly in the central and southern portions of the Iberian, Italian, Hellenic and Turkish peninsulas and in areas of southeastern Europe (e.g. Romania and Bulgaria), the Middle East, northern Africa and major Islands (Corsica, Sardinia and Sicily). Most Ice-Cap areas of the Alps are also projected to disappear. These effects are due to a large warming and pronounced decrease in precipitation, especially during the spring and summer seasons. In addition, fine scale topography and coastline features affect the aridity change signal. We identify the southern Mediterranean as a region particularly vulnerable to water stress and desertification processes under climate change conditions.

Reply to comment by M. F. Meier et al. on “The potential for sea level rise: New estimates from glacier and ice cap area and volume distributions”

Reply to comment by M. F. Meier et al. on “The potential for sea level rise: New estimates from glacier and ice cap area and volume distributions”

Comment on “The potential for sea level rise: New estimates from glacier and ice cap area and volume distribution” by S. C. B. Raper and R. J. Braithwaite

Comment on “The potential for sea level rise: New estimates from glacier and ice cap area and volume distribution” by S. C. B. Raper and R. J. Braithwaite

Simulation of Vatnajökull ice cap dynamics

We apply a coupled model of ice sheet dynamics and subglacial hydrology to investigate the dynamics and future evolution of the Vatnajökull ice cap, Iceland. In this paper we describe a new theoretical approach to introducing longitudinal stress coupling in the ice dynamics solution, and we analyze our ability to simulate the main features of Vatnajökull, with and without longitudinal stress effects. Equilibrium ice cap configurations exist for Vatnajökull but under a narrow range of climatic boundary conditions. Equilibrium reconstructions have an average ice thickness greater than what is observed at Vatnajökull, consistent with our inability to capture surge dynamics in Vatnajökull's outlet glaciers. Hydrological regulation of basal flow, longitudinal stress coupling, and a simple parameterization of the subglacial heat flux from Vatnajökull's geothermal cauldrons all help to reduce average ice thickness in the equilibrium reconstructions, but cases that reproduce the present‐day ice volume have an ice cap area that is 5–10% less than the actual ice cap. Present‐day reconstructions that adopt a realistic climate spin‐up for the period 1600–1990 provide improved fits to the modern‐day ice cap geometry. This indicates that climatic disequilibrium also plays a significant role in dictating Vatnajökull's morphology. Simulations for the period 1600–2300 illustrate that air temperature is the dominant control on Vatnajökull's volume and area. Longitudinal stress coupling and hydrological coupling both increase Vatnajökull's sensitivity to future warming.)

Sensitivity of Vatnajökull ice cap hydrology and dynamics to climate warming over the next 2 centuries

The sensitivity of Vatnajökull ice cap to future climate change is examined using spatially distributed coupled models of ice dynamics and hydrology. We simulate the evolving ice cap geometry, mass balance, velocity structure, subglacial water pressures and fluxes, and basin runoff in response to perturbations to a 1961–1990 reference climatology. For a prescribed warming rate of 2°C per century, simulated ice cap area and volume are reduced by 12–15% and 18–25% within 100 years, respectively. Individual outlet glaciers experience 3–6 km of retreat in the first 100 years and a total retreat of 10–30 km over 200 years. For the same applied warming our results suggest a maximum increase in glacier‐derived runoff of ∼25% after 130 years. Ice cap thinning and retreat alters Vatnajökull's subglacial hydraulic catchment structure in the simulations, with up to several kilometers of local hydraulic divide migration. This serves to redistribute water among the major outlet rivers and, in extreme cases, to isolate river basins from glacially derived runoff. Glacier discharge from northern and northwestern Vatnajökull (distal from the coast) appears to be the most robust to climate warming, while discharge from Vatnajökull's southern margin (proximal to the coast) is particularly vulnerable. The latter reflects pronounced changes in the geometry of the southern outlet glaciers and has implications for glacier flood routing and frequency.

The potential for sea level rise: New estimates from glacier and ice cap area and volume distributions

Projections of sea‐level rise from mountain glaciers and ice caps for the next century and beyond should be based on an assessment of the ice available for melting. Projections to date are based on all regions except Greenland and Antarctica (the latter are considered separately by the IPCC), yet no sound estimates for the appropriate volume of ice and its potential for sea level rise are evident in the literature. An ice cap data set is compiled allowing the separate treatment of glacier area coverage data. Glacier inventory data are comprehensive enough in some regions to allow the estimation of glacier size distributions. The differences in the distributions are related to a metric of the regional topographic variability, allowing glacier size distributions to be estimated on a 1° latitude longitude grid of cells containing glaciers. Appropriate volume‐area scaling for glaciers and for ice caps gives global estimates of glacier and ice cap volumes by size class. This leads to an estimate of the total ice volume of 0.087 ± 0.010 106 km3 and a sea level rise equivalent of 0.241 ± 0.026 m. The glaciers and ice caps contribute 41% and 59% to these estimates respectively. These values are based on data sets compiled during several decades, mainly in the second half of the 20th Century. We compare our results to published results that include the glaciers and icecaps at the margins of the Greenland and Antarctic ice sheets.

The background level of the summer tropospheric aerosol, sulphur dioxide and ozone over Greenland and the North Atlantic Ocean

A description is given of airborne measurements over Greenland and the surrounding seas of the concentration and size of Aitken nuclei and large nuclei, the concentration of cloud nuclei at a supersaturation of 1%, the concentration of ice nuclei activated at −20°C, the chemical nature of the tropospheric aerosol, the concentration of sulphur dioxide and ozone. The Aitken nuclei concentrations were generally log-normally distributed in the range of less than a 100 to 10 4 cm −3 with strong peaks of nuclei concentrations appearing in widely distributed thin layers superimposed on the background concentrations below 500 cm −3. The geometric mean value was 960 cm −3. The particle size distributions of the Aitken nuclei fluctuated widely, showing spectra of mono-, bi- and trimodal shapes. The particle size spectra are grouped by similarities in shape and their frequencies of occurrence are reported. The size spectra strongly indicate that formation of fresh nuclei by gas phase reactions is a common phenomenon in summer tropospheric air over Greenland and adjacent seas. The large nuclei concentrations were generally log-normally distributed in the region 0.3–300 cm −3 correlating in most cases with the Aitken nuclei concentrations. The geometric mean was 9 cm −3. The size distribution of the large nuclei covers the range 0.3–3 μm dia. and follows a power law above 0.4 μm. Cloud nuclei concentrations are reported for the North Sea and the North Atlantic only, the concentrations were normally low, nearly 50% of the measured concentrations were below 12 cm −3. Peak concentrations of up to 500 cm −3 were measured during a cold front passage. Ice nuclei concentrations were in the range of 0.01–0.1 1 −1. Samples taken for analysis of particulate sulphur compounds gave concentrations in the range 30–110·10 −9 g S m −3 over the nearby seas and 35–220·10 −9 g S m −3 over the ice cap. Measurements of sulphur dioxide gave concentrations in the range 50–725·10 −9 g SO 2 m −3 over the nearby sea areas and 60–1950·10 −9 g SO 2 m −3 in samples taken over the ice cap. A correlation coefficient between particulate sulphur and sulphur dioxide of 0.92 was found for samples taken over the sea areas, whereas a negative correlation between samples from the ice cap areas is dubious. Neutron activation analyses were performed for elements with a potential contribution from ground surface, volcanoes and anthropogenic activities. The volumes of the samples (50–100 m 3) were, however, too low to give reliable results. The mean concentration of ozone measured over the ice cap was 34 ppb, higher with a 90% level of confidence than the mean concentration of 30 ppb, measured over the nearby seas. No correlation between ozone and altitude was found at a 95% level of significance. Measurements of Aitken nuclei concentrations taken on the surface of the ice cap and showing only small variations around 150 cm −3, were strikingly different from the airborne measurements. Air mass trajectories, computed for selected events, show that the air sampled had within its recent history passed over Northern Canada. Greenland or the arctic seas.

Deglaciation and Isostasy in the Sukkertoppen Ice Cap Area, West Greenland

Deglaciation and Isostasy in the Sukkertoppen Ice Cap Area, West Greenland

Deglaciation and Isostasy in the Sukkertoppen Ice Cap Area, West Greenland

Three groups of landforms of deglaciation are analyzed, namely those associated with (1) the disappearance of Inland ice (main Greenland ice sheet), (2) the withdrawal of local Sukkertoppen ice, and (3) the changing of relative sea level. Consideration of their interrelationships in space and time allows a reconstruction of the process of deglaciation. There was an overall westerly movement of Inland ice across the area and this persisted during the early stages of deglaciation. Later stages of deglaciation reflect progressive downwasting with ice persisting in the troughs while adjacent plateau areas became free of ice. The highest marine limit is at 123 m and this incursion of the sea took place ca. 8,800 to 9,000 radiocarbon years BP. Local Sukkertoppen ice appears to have played an insignificant role during this main phase of deglaciation. Subsequently several Sukkertoppen outlet glaciers have advanced over marine deposits. The paper concludes with consideration of some wider implications. The importance of downwasting and meltwater activity during deglaciation is stressed. Also it is noted that isostatic recovery follows the Greenlandic pattern with high initial rates of uplift, apparently ceasing ca. 3,000 to 5,000 years BP. Unlike arctic Canada and Scandinavia where uplift has continued to the present day, the continued existence of a major ice sheet in Greenland is probably responsible for this recent stabilization. Finally, it is suggested that the last Inland ice sheet accomplished little erosion in the area compared to earlier ice sheets.

Oscillations of level in the belts peripheral to the Pleistocene ice-caps

A Test of Isostasy The theory of isostasy is widely favored as an explanation of recent uplifts in the glaciated tracts of North America and Europe. If the earth’s crust sinks after a heavy, extensive load of ice is put on it, and rises after that ice melts; if the crust so behaves each time that one and the same region is glaciated and deglaciated; if similar behavior were proved in separate areas—eastern Canada, the British Isles, Scandinavia, British Columbia, Patagonia, and Antarctica—the theory would almost become certainty. As a matter of fact, field studies have been largely confined to but three of the greater ice-cap areas and in each case to uplift following the latest deglaciation. Complete testing of the isostatic theory after the manner described is evidently much more difficult than the partial test so far applied. The sinking under load is in small part due. to purely elastic compression, . . .