Plateau Ice Cap Research Articles

Glacial landscape and paleoglaciation in Terra Sabaea: Evidence for a 3.6 Ga polythermal plateau ice cap

In a previous study, we demonstrated with a comparative morphometrical analysis the first morphometric evidence of a glacial landscape composed of glacial cirques and glacial valleys in the south of Terra Sabaea at an elevation > 1000m in two impact craters and one mountain. The purpose of this study is to use the same method to seek other geomorphologic evidence of glacial landscapes elsewhere in Terra Sabaea. Based on a comparison between current and old glacial landscapes on Earth and Mars, we identified 81 glacial valleys and possible evidence for a former plateau ice cap dated at 3.6 Ga at the highest elevation in Terra Sabaea. The identified glacial valleys have the same morphometric properties as terrestrial and martian glacial valleys with U-shaped cross-sectional profiles, a V-index >0.2, a length to with ratio >1 and a cross-sectional area to drainage area ratio four times higher than the fluvial ones. Moreover, these properties are different from terrestrial and martian fluvial valleys. We did not find well preserved glacial cirques in this area, this absence questions the origin of glacial valleys. However, the presence of an extensive flat plateau, from which the long valleys radiate, could have hosted an ancient plateau ice cap which was the source of these glacial valleys. A comparison with the Cantal and the Shaluli Shan in the southeastern Tibetan plateau on Earth reveals morphometrical similarities with our study area. In fact, long glacial valleys, originating radially from a plateau at higher elevation are characteristics of an ancient plateau ice cap. This analysis allowed us to propose a polythermal regime for martian glacial landscape, namely a cold-based ice cap except at the margin where the regime is warmed-based due to the steeper topography. This topography created shear stress which increased the heat at the base of the ice and created the outlet glacial valleys. Near the plateau, the radial valleys are U-shaped with a V-index >0.2 but downstream, to the low elevation area, these valleys become more V-shaped with a V-index around 0.1. This hypothesis is supported by the presence of an open-basin paleolake making the transition between inlet glacial valleys upstream and an outlet V-shaped valley downstream. So the morphometry of the radiating valleys suggests that liquid water played a role in the formation of this landscape.

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

Abstract. 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.

Dartmoor's overlooked glacial legacy

Traditionally regarded as a relict permafrost and periglacial landscape that lay beyond the limits of Pleistocene glaciation, the granite uplands of northern Dartmoor in south‐west England in fact contain geomorphological evidence for the former existence of a plateau ice cap, making the area the location of the southernmost independent glacier mass in the British Isles. In addition to weakly U‐shaped valleys, the most prominent evidence comprises arcuate and linear bouldery ridges and hummocky valley floor drift, which are interpreted as latero‐frontal moraines deposited by the outlet glacier lobes of a plateau ice cap. Inset sequences of these depositional landforms, in association with meltwater channels, demarcate the receding margins of the glacier lobes. A numerical model of ice cap development shows that a predominantly thin plateau icefield type glaciation is required in order to produce significant ice flow into surrounding valleys. The highest and most extensive plateau areas were occupied by ice for the longest cumulative period of time throughout the Pleistocene, thereby explaining: (1) the lack of tors in such areas as the product of ‘average’ glacial conditions preferentially removing tors or dampening their production rates, (2) the survival of high relief tors during glaciation if they occupied summits too narrow to develop thick and erosive glacier ice, and (3) the survival of subdued tors in areas glaciated less regularly during the Pleistocene.

Evolution of a Lateglacial mountain icecap in northern Scotland

Detailed geomorphological mapping of the Beinn Dearg massif, northern Scotland, was conducted to examine the maximum (Younger Dryas) extent, and earlier interstadial evolution, of an icecap that existed during the Lateglacial period (14.7–11.7 cal. ka BP). Landform evidence indicates a plateau icecap configuration during the Younger Dryas. The interpreted age is supported by new cosmogenic exposure ages and previously reported interstadial sediments beyond the icecap margin. The reconstructed Younger Dryas Beinn Dearg icecap covered 176 km2. Equilibrium line altitudes (ELAs) of ∼570–580 m were calculated for the icecap as a whole. The empirically reconstructed icecap is compared with recent numerical model simulations. The two methods produce an icecap with a similar configuration; however, differences are apparent in the extent of eastern and western outlets (±1–5 km), and in the spatial variation of ELAs. Results suggest that the numerical simulation overestimates the western and underestimates the eastern icecap extent. We attempt to quantify these differences in terms of icecap mass balance and assess their possible causes. Geomorphological evidence for the pre-Younger Dryas icecap configuration indicates that the Beinn Dearg massif remained an important source during earlier deglaciation. In contrast, the neighbouring Fannich mountains acted as an ‘unzipping’ zone, and were ice-free on their northern side by the Allerod (Greenland Interstadial 1c to 1a). Deglaciation continued over the western Beinn Dearg plateau, with the possibility that glaciers remained in some central and eastern catchments prior to (Younger Dryas) icecap (re)growth.

Late Quaternary glaciation and equilibrium-line altitudes of the Mayan Ice Cap, Guatemala, Central America

The Sierra los Cuchumatanes (3837 m), Guatemala, supported a plateau ice cap and valley glaciers around Montaña San Juan (3784 m) that totaled ∼ 43 km 2 in area during the last local glacial maximum. Former ice limits are defined by sharp-crested lateral and terminal moraines that extend to elevations of ∼ 3450 m along the ice cap margin, and to ca. 3000–3300 m for the valley glaciers. Equilibrium-line altitudes (ELAs) estimated using the area–altitude balance ratio method for the maximum late Quaternary glaciation reached as low as 3470 m for the valley glaciers and 3670 m for the Mayan Ice Cap. Relative to the modern altitude of the 0°C isotherm of ∼ 4840 m, we determined ELA depressions of 1110–1436 m. If interpreted in terms of a depression of the freezing level during maximal glaciation along the modern lapse rate of − 5.3°C km − 1 , this ΔELA indicates tropical highland cooling of ∼ 5.9 to 7.6 ± 1.2°C. Our data support greater glacial highland cooling than at sea level, implying a high tropical sensitivity to global climate changes. The large magnitude of ELA depression in Guatemala may have been partially forced by enhanced wetness associated with southward excursions of the boreal winter polar air mass.

Re-evaluating the Relevance of Vegetation Trimlines in the Canadian Arctic as an Indicator of Little Ice Age Paleoenvironments

The origin of trimlines associated with the so-called “lichen-free” areas in the Canadian Arctic has been attributed both to perennial snowfield expansion during the Little Ice Age (LIA) and to seasonally persistent snow cover in more recent times. Because of the disparate hypotheses (ecological versus paleoclimatic) regarding the formation of these trimlines, their use as a paleoclimatic indicator has been abandoned for more than two decades. We re-examine this debate and the validity of the opposing hypotheses in the light of new regional mapping of trimlines across the Queen Elizabeth Islands (QEI). The ecological hypothesis—insufficient duration of the growing season resulting from seasonally persistent snow cover—fails to account for the poikilohydric nature of lichens and their ability to endure short growing seasons. It cannot adequately explain the existence of sharp trimlines or account for the occurrence of those trimlines on sparsely vegetated carbonate terrain. Furthermore, trimlines outlining the former extent of thin plateau ice caps are accordant with trimlines associated with former perennial snowfields, indicating that these trimlines record snow and ice expansion during the LIA rather than the seasonal persistence of more recent snow cover. We suggest that these features represent an important LIA climate indicator and should therefore be used for paleoclimatic reconstruction.

Palaeoglaciation of Parque Natural Lago de Sanabria, northwest Spain

Detailed geomorphological mapping provides evidence for at least three phases of glaciation in the Parque Natural Lago de Sanabria, in northwest Spain. The most extensive glaciation was characterised by a large plateau ice cap. A combination of geomorphological evidence and glacier modelling indicates that this ice cap covered an area of more than 440 km 2, with a maximum ice thickness of c. 300 m and outlet glaciers reaching as low as 1000 m. This represents the largest ice mass in Iberia outside the Pyrenees and one of the largest in the mountains of southern Europe and the Mediterranean region. Radiocarbon dates from the base of lacustrine sequences appear to suggest that the most extensive phase of ice-cap glaciation occurred during the last cold stage (Weichselian) with deglaciation occurring before 14–15 ka 14C BP. A second phase of glaciation is recorded by the moraines of valley glaciers, which may have drained small plateau ice caps; whilst a final phase of glaciation is recorded by moraines in the highest cirques.

Ice thickness, internal structure and subglacial topography of Bowles Plateau ice cap and the main ice divides of Livingston Island, Antarctica, by ground-based radio-echo sounding

AbstractWe present the results of low-frequency (20 MHz) radio-echo sounding (RES) carried out in December 2000 and December 2006 on the main ice divides of Livingston Island, South Shetland Islands (SSI), Antarctica, and Bowles Plateau, Antarctica, respectively, as well as high-frequency (200 MHz) RES on the latter, aimed at determining the ice thickness, internal structure and subglacial relief. Typical ice thickness along the main ice divides is ~150 m, reaching maxima of ~200 m. On Bowles Plateau the ice is much thicker, with an average of 265 m and maxima of ~500 m. The bed below the main ice divides is above sea level, while part of the outlet glaciers from Bowles Plateau lies significantly below sea level, down to –120 m. The strong scattering of the radio waves in the areas under study constitutes further evidence that the ice in the accumulation area of the ice masses of the SSI is temperate. Typical thickness of the firn layer in Bowles Plateau is 20–35 m, similar to that found in King George ice cap. A strong internal reflector within the firn layer, interpreted as a tephra layer from the 1970 eruption at Deception Island, has allowed a rough estimate of the specific mass balances for Bowles Plateau within 0.20–0.40ma–1w.e., as average values for the period 1970–2006.

Mass balance and area changes of four high arctic plateau ice caps, 1959–2002

Small, stagnating ice caps at high latitudes are particularly sensitive to climatic fluctuations, especially with regard to changes in ablation season temperature. We conducted mass balance measurements and GPS area surveys on four small High Arctic plateau ice caps from 1999–2002. We compared these measurements with topographic maps and aerial photography from 1959, and with previously published data. Net mass balance (bn) of Murray Ice Cap was −0.49 (1999), −0.29 (2000), −0.47 (2001), and −0.29 (2002), all in meters of water equivalent (m w.eq.). The mass balance of nearby Simmons Ice Cap was also negative in 2000 (bn=−0.40 m w.eq.) and in 2001 (bn=−0.52 m w.eq.). All four ice caps experienced substantial marginal recession and area reductions of between 30 and 47% since 1959. Overall, these icecaps lost considerable mass since at least 1959, except for a period between the mid‐1960s and mid‐1970s characterized regionally by reduced summer melt, positive mass balance, and ice cap advance. The regional equilibrium line altitude (ELA) is located, on average, above the summits of the ice caps, indicating that they are remnants of past climatic conditions and out of equilibrium with present climate. The ice caps reached a Holocene maximum and were several times larger during the Little Ice Age (LIA) and their current recession reflects an adjustment to post‐LIA climatic conditions. At current downwasting rates the ice masses on the Hazen Plateau will completely disappear by, or soon after, the mid‐21st century.

Recent recession of a small plateau ice cap, Ellesmere Island, Canada

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Late Quaternary glacial history of Lake Hazen Basin and eastern Hazen Plateau, northern Ellesmere Island, Nunavut, Canada

The glacial history of the broad interior of northeastern Ellesmere Island is first documented here. Studies of glacial geomorphology and marine and lacustrine sedimentology indicate that the region was inundated by cold-based ice emanating from the Grant Land Mountains sector of the Innuitian Ice Sheet during the last glacial maximum. Retreat of coalescent, marine-based Ellesmere and Greenland ice from Robeson Channel had started by 10.1 ka BP and reached the mouths of many fiords along southeast Hazen Plateau by 8 ka BP. Proglacial meltwater channels emanating from plateau ice caps, crosscut lateral meltwater channels marking the retreat of Grant Land Mountain ice. The crosscutting is interpreted to reflect an early Holocene growth of plateau ice caps concurrent with the retreat of marine-based margins. This suggests that initial regional ice retreat was eustatically controlled. Stabilization of glacier margins at the heads of fiords occurred by 7.5-7 ka BP, after which land-based margins retreated as little as 10 km by 6 ka BP. Across much of northeastern Hazen Plateau, however, Grant Land Mountain ice retreated more rapidly. This more rapid retreat was accentuated by the impoundment of proglacial lakes against the plateau to the south and the subsequent breakup of ice by calving. Glaciers continued to occupy much of Lake Hazen Basin at 5.3 ka BP, after which they broke up rapidly in a proto-Lake Hazen, retreating to margins at, or behind, those of the present by 5 ka BP.

Late Quaternary glacial history of Lake Hazen Basin and eastern Hazen Plateau, northern Ellesmere Island, Nunavut, Canada

The glacial history of the broad interior of northeastern Ellesmere Island is first documented here. Studies of glacial geomorphology and marine and lacustrine sedimentology indicate that the region was inundated by cold-based ice emanating from the Grant Land Mountains sector of the Innuitian Ice Sheet during the last glacial maximum. Retreat of coalescent, marine-based Ellesmere and Greenland ice from Robeson Channel had started by 10.1 ka BP and reached the mouths of many fiords along southeast Hazen Plateau by 8 ka BP. Proglacial meltwater channels emanating from plateau ice caps, crosscut lateral meltwater channels marking the retreat of Grant Land Mountain ice. The crosscutting is interpreted to reflect an early Holocene growth of plateau ice caps concurrent with the retreat of marine-based margins. This suggests that initial regional ice retreat was eustatically controlled. Stabilization of glacier margins at the heads of fiords occurred by 7.5-7 ka BP, after which land-based margins retreated as little as 10 km by 6 ka BP. Across much of northeastern Hazen Plateau, however, Grant Land Mountain ice retreated more rapidly. This more rapid retreat was accentuated by the impoundment of proglacial lakes against the plateau to the south and the subsequent breakup of ice by calving. Glaciers continued to occupy much of Lake Hazen Basin at 5.3 ka BP, after which they broke up rapidly in a proto-Lake Hazen, retreating to margins at, or behind, those of the present by 5 ka BP.

Age of Lassen Peak, California, and implications for the ages of late Pleistocene glaciations in the southern Cascade Range

Lassen Peak is a large volcanic dome of late Pleistocene age at the southern end of the Cascades arc. This dacitic dome has a complex phenocryst assemblage of mixed-magma origin and has been effectively dated for the first time using the 40 Ar/ 39 Ar technique. Emplacement of the dome occurred after an advance of late Pleistocene glaciers from an older volcanic cone to the southwest and from a large volcanic plateau to the east. Emplacement of the Lassen Peak dome before the latest major Pleistocene glaciation—correlated by previous workers with the Tioga glaciation of the Sierra Nevada—formed a high peak that intercepted some of the precipitation that previously had fed the plateau ice cap, forming a 10-km-long glacier from a cirque on the northeast side of the peak. The weighted mean 40 Ar/ 39 Ar age of the dacite of Lassen Peak is 28.3 ± 2.7 ka. Comparison of its remanent magnetic direction to that of sedimentary deposits at Mono Lake, California, indicates a correlation to strata of 27 ± 1 ka. The dacite of Kings Creek, which erupted from the site of Lassen Peak before a glacial advance that predated the Lassen Peak dome, overlies peat that has a U-Th-calibrated 14 C age of 37.6 ± 0.2 ka. The dacite of Kings Creek yielded a 40 Ar/ 39 Ar age of 32 ± 17 ka. The paleomagnetism of this dacite is similar to that of Mono Lake sediments of 35 ± 1 ka age. Thus, a late Pleistocene glacial advance probably began in the Lassen region between about 35 and 27 ka.

A reconstruction of glacial events in southeastern New Brunswick

Sedimentological and petrographical data obtained from five sections located north and south of the Caledonian Highlands in southeastern New Brunswick demonstrate the existence of three main till units and one glaciofluvial unit, which have been grouped in four distinct lithostratigraphic units. The lower till was deposited by a glacier that overrode the Caledonian Highlands from northwest to southeast and advanced as far as Nova Scotia during Middle(?) to Late Wisconsinan times. The overlying middle till from the north provides evidence that ice continued to advance across the Highlands from northwest toward southeast and then was partially overwhelmed by another glacier that was advancing southwest along the southern border of the Highlands: this glacier deposited a coeval middle till. During Late Wisconsinan deglaciation, ice separated into two masses: a residual ice cap with radial outflow from the Highlands; and a lobe in the Chignecto Bay, retreating toward the northeast. The existence of a plateau ice cap is demonstrated by the presence of till and glaciofluvial deposits in the upper part of all surveyed sections, and is supported by the sequence of ice flow patterns recorded by striae and the centrifugal distribution of meltwater flow indicators. The weak development of soils, the fresh appearance of till and morainic landforms, and the lack of periglacial features throughout the area, especially on the Highlands, all favour the interpretation that the Caledonian Highlands were not a nunatak during the glacial maximum of the Late Wisconsinan Substage.

The late Quaternary history of Greely Fiord and its tributaries, west-central Ellesmere Island

Moraines and meltwater channels mark the limit of the last glaciation that interfingered with the sea around the perimeter of Greely Fiord and its tributaries. The extent of this ice advance was dictated predominantly by its proximity to the sea. Consequently, the large tidewater glaciers at the fiord heads today were so constrained by calving that they advanced only 5–10 km. Similarly, grounding-line deposits from widespread plateau ice caps also terminate just below marine limit. The most extensive outlet glaciers, which advanced 20–35 km beyond present margins, are simply those that had access to the most extensive terrain above marine limit, i.e., the northwest margin of the Agassiz Ice Cap.Forty-one new 14C dates are presented. The onset of the last ice advance must predate marine shells collected from sediments overlying a former grounding line when sea level was 122 m higher than present. At this site, the lowermost shells collected from glaciomarine silts dated 38 070 ± 410 BP, whereas a surface sample 13 m above them dated 22 900 ± 190 BP. Although both dates may be minimum estimates, they are nonetheless associated with an ice margin that retreated only a few kilometres by 7850 BP, suggesting the maintenance of the glacioisostatic loading (and relative sea level) during the interim. Nearby, shells in growth position overlying bedrock confirm that relative sea level was > 83 m asl by 38 010 ± 410 BP (minimum age). These marine deposits lie outside the last ice limit and are not overlain by glacigenic sediments.Distal to the last ice limit, Greely Fiord was occupied by the full glacial sea, whose limit is marked by discontinuous beaches and wave-cut benches. The full glacial sea rises from 116 m north of Greely Fiord to a maximum elevation of 148 m bordering its south shore from which it descends to 112 m asl near the head of Cañon Fiord. Numerous 14C dates on shells collected within 8 m of marine limit show that the full glacial sea remained stable from at least 8400 to 7400 BP. Several other shell samples collected ~20 m below marine limit are much older (> 22 000 BP). The position of relative sea level between ca. 8000 and > 22 000 BP is uncertain; however, stratigraphic evidence for an intervening regression has not been found.The modest extent of the last ice limit encircling Greely Fiord, together with its occupancy by the full glacial sea, is fully compatible with the paleogeography previously reported from northeast Ellesmere Island and northwest Greenland. Furthermore, this data base provides a reinterpretation of a 500 km transect previously reported along west-central Ellesmere Island to the south and affirms that the Innuitian Ice Sheet, defined sensu stricto for the last glaciation, is supplanted by the full glacial Innuitian Sea, which penetrated the Queen Elizabeth Islands, constraining the last ice limit.

Recent glacial history and climatic change, Bergsfjord, Troms-Finnmark, Norway

Systematic documentation of climatic change using historical records of glacier fluctuations in North Norway is complicated by the strong topographic control exerted on glacier and ice-cap development in plateau regions. Ice avalanches from high plateaux maintain valley glaciers up to 600 m below in the surrounding valleys. Ice-marginal recession due to changing mass balance on the plateau ice caps has reduced ice avalanching and contributed to the subsequent decline of outlet and valley glaciers. The plateau ice caps on the Bergsfjord Peninsula occupy a critical altitudinal threshold between 900 and 1200 m which is particularly sensitive to recent climatic change. Patterns of glacier response are recorded with the aid of historical records and field mapping. The changes in ice distribution are linked to both fluctuations in mass balance and to important topographic controls on summit ice caps.

Thermal regime and geomorphology of plateau ice caps in northern Norway: Observations and implications

Research Article| November 01, 1988 Thermal regime and geomorphology of plateau ice caps in northern Norway: Observations and implications Anne F. Gellatly; Anne F. Gellatly 1Department of Geography, Plymouth Polytechnic, Plymouth PL4 8AA, England Search for other works by this author on: GSW Google Scholar John E. Gordon; John E. Gordon 2Nature Conservancy Council, Northminster House, Peterborough PE1 1UA, England Search for other works by this author on: GSW Google Scholar W. Brian Whalley; W. Brian Whalley 3Department of Geography, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland Search for other works by this author on: GSW Google Scholar James D. Hansom James D. Hansom 4Department of Geography, University of Sheffield, Sheffield S1O 2TN, England Search for other works by this author on: GSW Google Scholar Author and Article Information Anne F. Gellatly 1Department of Geography, Plymouth Polytechnic, Plymouth PL4 8AA, England John E. Gordon 2Nature Conservancy Council, Northminster House, Peterborough PE1 1UA, England W. Brian Whalley 3Department of Geography, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland James D. Hansom 4Department of Geography, University of Sheffield, Sheffield S1O 2TN, England Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1988) 16 (11): 983–986. https://doi.org/10.1130/0091-7613(1988)016<0983:TRAGOP>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Anne F. Gellatly, John E. Gordon, W. Brian Whalley, James D. Hansom; Thermal regime and geomorphology of plateau ice caps in northern Norway: Observations and implications. Geology 1988;; 16 (11): 983–986. doi: https://doi.org/10.1130/0091-7613(1988)016<0983:TRAGOP>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The ice caps on high plateaus of northern Norway (lat 70°N) can be grouped according to altitude. The highest ice caps (> 1500m) are dry-based and are slowly retreating to reveal undisturbed block fields; they appear to be found only in southern Lyngen. Ice on plateaus at lower elevations (≤ 1500 m above sea level) is wet-based and has produced extensive striated bedrock surfaces and moraine sequences on the glacier forefields. We propose that this geomorphological distinction can be applied to other plateau glaciers to identify present and, in particular, former basal thermal regimes. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Radiation and Cloud Observations on a High Arctic Plateau Ice Cap

AbstractHourly measurements of incoming short-wave and long-wave radiation, surface albedo, and net radiation were made on and around a plateau ice cap on north-eastern Ellesmere Island during the summers of 1982 and 1983. These data were stratified by cloud type and amount. All cloud types increased incoming long-wave radiation, especially low dense clouds, fog, and clouds associated with snowfall. Relative transmission of incoming short-wave radiation, expressed as a percentage of clear-sky radiation receipts, was high for all cloud types compared to clouds at lower latitudes. With high surface albedo (≥0.75), net radiation was strongly and positively correlated with net long-wave radiation but showed little relationship to net short-wave radiation. By contrast, with low surface albedo (≤0.20) net radiation was negatively correlated with net long-wave radiation but positively correlated with net short-wave radiation. Under high-albedo conditions, an increase in cloudiness led to higher values of net radiation but under low-albedo conditions net radiation decreased as cloud cover increased. Survival of a snow cover would seem to be favoured if the seasonal decline in albedo is accompanied by a corresponding increase in cloudiness.

Radiation and Cloud Observations on a High Arctic Plateau Ice Cap

AbstractHourly measurements of incoming short-wave and long-wave radiation, surface albedo, and net radiation were made on and around a plateau ice cap on north-eastern Ellesmere Island during the summers of 1982 and 1983. These data were stratified by cloud type and amount. All cloud types increased incoming long-wave radiation, especially low dense clouds, fog, and clouds associated with snowfall. Relative transmission of incoming short-wave radiation, expressed as a percentage of clear-sky radiation receipts, was high for all cloud types compared to clouds at lower latitudes. With high surface albedo (≥0.75), net radiation was strongly and positively correlated with net long-wave radiation but showed little relationship to net short-wave radiation. By contrast, with low surface albedo (≤0.20) net radiation was negatively correlated with net long-wave radiation but positively correlated with net short-wave radiation. Under high-albedo conditions, an increase in cloudiness led to higher values of net radiation but under low-albedo conditions net radiation decreased as cloud cover increased. Survival of a snow cover would seem to be favoured if the seasonal decline in albedo is accompanied by a corresponding increase in cloudiness.

Mass Balance of Two High Arctic Plateau Ice Caps

AbstractMass-balance measurements have been renewed on two small ice caps on north-eastern Ellesmere Island. Original stake networks were established in 1972 and 1976. Since then, both ice caps have experienced significant mass losses averaging –70 to –140 kg m−2a−1. They have also decreased in area. The equilibrium line in this area has averaged around 1150 m for the last decade or so. The ice caps are remnants of former climatic conditions and are out of equilibrium with contemporary climate.