Glacier Expansion Episodes Research Articles

Palaeoenvironmental change and glacier fluctuations in the high Tian Shan Mountains during the last millennium based on sediments from Lake Ala Kol, Kyrgyzstan

A suite of limnological proxies measured in clastic sediments of the glacier-fed Lake Ala Kol (NE Kyrgyzstan) document palaeoenvironmental change and glacier fluctuations in the central Tian Shan over the last millennium. Rock magnetic and geochemical data provide supporting evidence for three glacier expansion episodes occurring in 1200–1400 CE, 1500–1850 CE and 1900–1950 CE and glacier retreat periods during 1000–1200 CE and the intervening periods. The maximal glacier extent, as inferred from high κLF, Si/inc + coh, Ca/inc + coh and low ARM30/ARM, is recorded between 1500 and 1850 CE and corresponds to cold and wet conditions during the Little Ice Age in the high central Tian Shan. Periods of glacier waxing and waning recorded at Lake Ala Kol present a close correspondence to ice accumulation rate in the northern Tibetan Plateau, suggesting that precipitation changes are the main driver of glacier fluctuations in central Tian Shan during the last millennium, although temperature may have exerted a more complex influence on centennial timescales.

Glacier response to North Atlantic climate variability during the Holocene

Abstract. Small glaciers and ice caps respond rapidly to climate variations, and records of their past extent provide information on the natural envelope of past climate variability. Millennial-scale trends in Holocene glacier size are well documented and correspond with changes in Northern Hemisphere summer insolation. However, there is only sparse and fragmentary evidence for higher-frequency variations in glacier size because in many Northern Hemisphere regions glacier advances of the past few hundred years were the most extensive and destroyed the geomorphic evidence of ice growth and retreat during the past several thousand years. Thus, most glacier records have been of limited use for investigating centennial-scale climate forcing and feedback mechanisms. Here we report a continuous record of glacier activity for the last 9.5 ka from southeast Greenland derived from high-resolution measurements on a proglacial lake sediment sequence. Physical and geochemical parameters show that the glaciers responded to previously documented Northern Hemisphere climatic excursions, including the "8.2 ka" cooling event, the Holocene Thermal Maximum, Neoglacial cooling, and 20th century warming. In addition, the sediments indicate centennial-scale oscillations in glacier size during the late Holocene. Beginning at 4.1 ka, a series of abrupt glacier advances occurred, each lasting ~100 years and followed by a period of retreat, that were superimposed on a gradual trend toward larger glacier size. Thus, while declining summer insolation caused long-term cooling and glacier expansion during the late Holocene, climate system dynamics resulted in repeated episodes of glacier expansion and retreat on multi-decadal to centennial timescales. These episodes coincided with ice rafting events in the North Atlantic Ocean and periods of regional ice cap expansion, which confirms their regional significance and indicates that considerable glacier activity on these timescales is a normal feature of the cryosphere. The data provide a longer-term perspective on the rate of 20th century glacier retreat and indicate that recent anthropogenic-driven warming has already impacted the regional cryosphere in a manner outside the natural range of Holocene variability.

Glacier fluctuations of Muztagh Ata and temperature changes during the late Holocene in westernmost Tibetan Plateau, based on glaciolacustrine sediment records

AbstractLate Holocene glacier variations in westernmost Tibetan Plateau were studied based on the analysis of grain size, magnetic susceptibility, and elements from an 8.3 m long distal glaciolacustrine sediment core of Kalakuli Lake. Our results show that there are four glacier expansion episodes occurring in 4200–3700 calibrated years (cal years) B.P., 2950–2300 cal years B.P., 1700–1070 cal years B.P., and 570–100 cal years B.P. and four glacier retreat periods of 3700–2950 cal years B.P., 2300–1700 cal years B.P., 1070–570 cal years B.P., and 50 cal years B.P.–present. The four glacier expansion episodes are generally in agreement with the glacier activities indicted by the moraines at Muztagh Ata and Kongur Shan, as well as with the late Holocene ice‐rafting events in the North Atlantic. Over the last 2000 years, our reconstructed glacier variations are in temporal agreement with reconstructed temperature from China and the Northern Hemisphere, indicating that glacier variations at centennial time scales are very sensitive to temperature in western Tibetan Plateau.

Late Holocene glacial activity at Bromley Glacier, Cambria Icefield, northern British Columbia Coast Mountains, Canada

Retreating and downwasting glaciers in the British Columbia Coast Mountains are exposing the remains of forests buried during Holocene-age glacial advances. Despite recent progress in discerning the extent of these advances in the Pacific and Kitimat ranges of the southern and central Coast Mountains, comparatively little is known about the character of these advances in the Boundary Ranges of northwestern British Columbia. This research uses dendroglaciologic and radiocarbon analyses to describe late Holocene glacial advances at Bromley Glacier in the Cambria Icefield area. Four intervals of glacial expansion were identified at ca. 2470–2410, 1850, 1450, and 830 14C years BP. Absent were wood remains associated with mid-Holocene episodes of glacier expansion recorded at nearby sites. The late Holocene deposits described at Bromley Glacier are contemporaneous with those found at other glaciers in the southern Boundary Ranges and contribute to a growing understanding of the synchronous response of glaciers in this region to mass balance fluctuations during the Holocene.

The ‘little ice age’: re‐evaluation of an evolving concept

ABSTRACT. This review focuses on the development of the ‘Little Ice Age’ as a glaciological and climatic concept, and evaluates its current usefulness in the light of new data on the glacier and climatic variations of the last millennium and of the Holocene. ‘Little Ice Age’ glacierization occurred over about 650 years and can be defined most precisely in the European Alps (c. AD 1300–1950) when extended glaciers were larger than before or since. ‘Little Ice Age’ climate is defined as a shorter time interval of about 330 years (c. AD 1570–1900) when Northern Hemisphere summer temperatures (land areas north of 20°N) fell significantly below the AD 1961–1990 mean. This climatic definition overlaps the times when the Alpine glaciers attained their latest two highstands (AD 1650 and 1850). It is emphasized, however, that ‘Little Ice Age’ glacierization was highly dependent on winter precipitation and that ‘Little Ice Age’ climate was not simply a matter of summer temperatures. Both the glacier‐centred and the climate‐centred concepts necessarily encompass considerable spatial and temporal variability, which are investigated using maps of mean summer temperature variations over the Northern Hemisphere at 30‐year intervals from AD 1571 to 1900. ‘Little Ice Age’‐type events occurred earlier in the Holocene as exemplified by at least seven glacier expansion episodes that have been identified in southern Norway. Such events provide a broader context and renewed relevance for the ‘Little Ice Age’, which may be viewed as a ‘modern analogue’ for the earlier events; and the likelihood that similar events will occur in the future has implications for climatic change in the twenty‐first century. It is concluded that the concept of a ‘Little Ice Age’ will remain useful only by (1) continuing to incorporate the temporal and spatial complexities of glacier and climatic variations as they become better known, and (2) by reflecting improved understanding of the Earth‐atmosphere‐ocean system and its forcing factors through the interaction of palaeoclimatic reconstruction with climate modelling.

Holocene glacier history of Bjørnbreen and climatic reconstruction in central Jotunheimen, Norway, based on proximal glaciofluvial stream-bank mires

Holocene variations of Bjørnbreen, Smørstabbtinden massif, west-central Jotunheimen are reconstructed from the lithostratigraphy of two alpine stream-bank mires flooded episodically by meltwater. The approach uses multiple sedimentological indicators (weight loss-on-ignition, mean grain size, grain-size fractions, bulk density, moisture content and magnetic susceptibility), an a priori model of overbank deposition of suspended glaciofluvial sediments, a detailed chronology based on 56 radiocarbon dates, and a Little Ice Age sedimentological analogue. Rapid, late-Preboreal deglaciation was indicated by immigration of Betula pubescens by 9700 cal. BP. An interval of at least 3000 years in the early Holocene when glaciers were absent was interrupted by two abrupt episodes of glacier expansion around the time of the Finse Event, the first at ca 8270–7900 cal. BP (Bjørnbreen I Event) and the second at ca 7770–7540 cal. BP (Bjørnbreen II Event). Neoglaciation began shortly before ca 5730 cal. BP with gradual build-up to the maximum of the Bjørnbreen III Event at ca 4420 cal. BP. Later maxima occurred at ca 2750 cal. BP (Bjørnbreen IV Event) and at 1300, 1260, 1060 and 790 cal. BP (all within the Bjørnbreen V Event). Glaciers were smaller than today and possibly melted away on several occasions in the late Holocene (ca 3950, 1410 and 750 cal. BP). Minor maxima also occurred at ca 660 and 540 cal. BP, within the late Mediaeval Warm Period and the early Little Ice Age, respectively. The Little Ice Age maximum was dated to 213±25 BP (ca 205 cal. BP). The relative magnitudes of the main glacier maxima were determined: Erdalen Event>Little Ice Age Event (Bjørnbreen VI)>Bjørnbreen I (Finse Event) ≈ Bjørnbreen II>Bjørnbreen V⩾Bjørnbreen IV>Bjørnbreen III. These episodic events of varying magnitude and abruptness were used in conjunction with an independent summer-temperature proxy to reconstruct variations in equilibrium-line altitude (ELA) and a Holocene record of winter precipitation. Since the Preboreal, ELA varied within a range of about 390 m, and winter precipitation ranged between 40 and 160% of modern values. Winter precipitation variations appear to have been the main cause of these century- to millennial-scale Holocene glacier variations.

Proglacial lacustrine sediments from El Altar, Ecuador: evidence for late-Holocene climatic change

Late-Holocene glacier variations on El Altar, Ecuador, have been reconstructed from proglacial lacustrine sediments. Variations in bulk density and organic content in sediment cores from Laguna Verde, are interpreted as representing a record of the Neoglacial activity of the Obsipo Glacier. Two sedimentological units of laminated silt and clay represent two late-Holocene episodes of glacier expansion, which probably occurred during the last millennium and tentatively suggest a double 'Little Ice Age' signal. Reconstructed equilibrium-line altitudes on the Obispo Glacier seem to reflect changes in both precipitation and temperature, and the glacial fluctuations documented on El Altar are consistent with other evidence of environmental change from northern South America.

The Holocene glacial history of Lyngshalvöya, northern Norway: chronology and climatic implications

Up to four nested Neoglacial moraines occur in front of glaciers on Lyngshalvöya. Lichenometric measurements at 21 glaciers demonstrate that these represent five episodes of glacier expansion, one of which predated the Little Ice Age. Lichenometric, dendrochronological and historical evidence indicates that the oldest Little Ice Age moraines date to the mid‐18th century, and the youngest to A.D. 1910‐30. At nine small glaciers the A.D. 1910‐30 moraine represents the Neoglacial maximum; only larger glaciers were more extensive in the 18th century. It is inferred that conditions for glacier growth were less favourable in the 18th century than in A.D. 1880–1910 because of low winter snowfall. Comparison of the relative magnitude of 18th‐ and 20th‐century advances on Lyngshalvöya with those of southern Norway suggests that the diminished winter precipitation was due to the southerly location of the North Atlantic oceanic polar front in the 18th century, which resulted in a reduction in winter cyclonic activity in northern Scandinavia but in an increase in snowfall farther south.

Aranuian radiocarbon dates from moraines in the Mount Cook region, New Zealand

Abstract 18 new radiocarbon dates were obtained for organic materials, associated mainly with soils buried by till, from sites in the lateral moraines of Mount Cook glaciers, particularly the Tasman. The 23 New Zealand (i.e., Institute of Nuclear Sciences, DSIR, Lower Hutt) dates now available from the Tasman Glacier, taken at face value, indicate that there were glacier expansion periods there about 3450-3000, 2280, 1800-1620, 1200-900, 860, 680, 340, and < 250 radiocarbon years ago. Taking into account the statistical counting error, the ages of some of the date sets overlap. Excluding a few problematical age determinations, and those on whole soil samples, the full range of dates now available from moraines of Mount Cook glaciers (including those from the New Zealand laboratory and a laboratory in Hannover, West Germany), taken at face value, shows that glacier expansion episodes have occurred: c. 8000 years ago, probably in the 6th millennium B.P., c. 3690-3000, c. 2550-2280, c. 2110-1620, c. 1255-900...

The Fox permafrost tunnel: A late Quaternary geologic record in central Alaska

The Fox permafrost tunnel, which penetrates 110 m into frozen sediments of Gold-stream valley, provides a continuous exposure of fossiliferous silt and alluvium above schistose bedrock. Deposition of fluvial gravel was followed by a long interval of loess accretion and permafrost aggradation that was punctuated by episodes of thaw and of gullying and redeposition of silt. Imbricated sandy gravel above the bedrock contains lenses of finer alluvium that contain wood fragments and some rooted stumps. Radiocarbon dates indicate that the gravel is older than 40 ka, but absence of mature soil and weathering profiles at its upper contact indicates that fluvial activity must have continued until shortly before loess accretion began at the tunnel site. Silt is the most widespread depositional unit in the tunnel. This deposit is of eolian origin (loess), but some has been redeposited by slope processes. The silt units contain abundant ground ice as pore filings, lenses, wedges, and buried pond ice. Loess accretion was interrupted by a period when little loess accumulated and when large ice wedges formed in the lower loess unit and subsequently were truncated by thaw. Loess began forming sometime before 40 ka and was rapidly accreting by 39 ka under xeric conditions with open vegetation. A sharply decreased rate of loess accretion associated with local erosion and thaw between about 36 and 30 ka is marked by anomalous cation concentration values, lenses of buried sod, fossils indicative of moist to wet substrates, and truncated ice wedges beneath small frozen ponds or streamlets that occupied ice-wedge troughs. A later episode of rapid loess influx under drier conditions began after 30 ka and coincided with glacial advances of late Wisconsin age in the adjoining Alaska Range. Large ice wedges also formed in the upper loess unit, but only their bases are exposed in the tunnel, and their history of development is uncertain. Fanlike deposits of poorly sorted debris near the tunnel portal formed between about 12.5 and 11 ka during deep erosion of loess slopes under moister conditions. The deposits locally form two subunits: the younger over- whelmed a stand of tall willows on the floor of Goldstream valley between about 11.3 and 11.1 ka; the older may have formed about 1,000 yr earlier. Stratigraphic records elsewhere in central Alaska indicate variable middle Wisconsin environments followed by colder and drier conditions that began between 30 and 25 ka and persisted until perhaps 12.5 ka. Widespread loess erosion and redeposition subsequently occurred under moister and probably warmer conditions. Renewed early Holocene loess deposition may have been widespread, but its exact environmental controls are uncertain. Our data challenge three generally accepted concepts of late Quaternary periglacial processes in central Alaska. We contend that (1) many ice-wedge systems may have formed under interstadial conditions rather than full-glacial conditions, (2) episodes of rapid loess influx may have been partly out of phase with episodes of glacier expansion, and (3) redeposition of loess by solifluction, sheetwash, and gully formation may have been episodic and required conditions moister than those under which the loess initially accreted.

Radiocarbon dates for post-Otiran glacial activity in the Mount Cook region, New Zealand

Abstract Radiocarbon dates of organic deposits in the glacial moraines near Mount Cook show that there were episodes of glacier expansion about 8000, 1800, and 1000 years B.P. Correlations between the dated moraines and those in nearby areas are suggested

Major Neoglacial Glacier Expansion Episodes in Southern Norway: Evidences from Moraine Ridge Stratigraphy With14C Dates on Buried Palaeosols and Moss Layers

Excavations in the outermost end moraine ridges in front of three Jotunheimen glaciers exposed buried palaeosols and moss layers which were 14C dated. Pre-‘Little Ice Age’ Neoglacial maxima were indicated by 14C dates on various soil organic fractions at Styggedalsbreen and Leirbreen; the most probable dates for these maxima are ca.2700 calendar years B.P. and ca.1300 calendar years B.P. A ‘Little Ice Age’ maximum was confirmed by dates on Sphagnum moss layers at Storbreen. Use of replicate dates, dates on different kinds of organic material and on different fractions of soil organic matter were found useful in assessing the relative accuracy of the datings. It is concluded that the ‘Little Ice Age’ glacier expansion episode was the most extensive in southern Norway, but that in at least two other periods of Neoglacial time, glaciers expanded to similar dimensions. No evidence was found for Neoglacial expansion episodes earlier than ca.3000 14C years B.P. Attention is drawn to the temporal and spatial complexities of Neoglacial glacier fluctuations in the European Alps; although similar complexities are suspected for southern Norway and elsewhere in Scandinavia, doubt is expressed in the ability of current glacial stratigraphic approaches to reconstruct the finer details of a Neoglacial chronology. It is inferred that climatic deteriorations since the Preboreal chronozone have been of no greater magnitude than that of the ‘Little Ice Age’.

The pattern of Neoglacial glacier variations in the Okstindan region of northern Norway during the last three millennia

BOREAS Griffey, N. J. &amp; Worsley, P. 1978 03 01: The pattern of Neoglacial glacier variations in the Okstindan region of northern Norway during the last three millennia (Okstindan Research Project Report 26). Boreas, Vol. 7, pp. 1–17. Oslo. ISSN 0300–9483.Historical, lichenometrical and stratigraphical evidence is combined to establish a provisional history of Neoglacial glacier variation in a mountainous environment approx. 66oN. Attention is focussed on end moraine chronology. At five sites, derived organic materials have been located within end moraines and at two others in situ palaeosols occur buried beneath distal slopes. Organic rich samples from all the sites have been radiocarbon dated and the results permit the recognition of three major glacier expansion episodes, each of which contributes to the diachronous nature of the Okstindan outer Neoglacial limit. A widespread ‘Little Ice Age’ event with a maximum extent of probable eighteenth century age is confirmed. Limited areas of older moraine ridges peripheral to the ‘Little Ice Age’ maximal limit appear to date from about 3000‐2500 14C years B.P. and a younger period tentatively dated as about 1250‐1000 14C years B. P. which agrees with recent data from Engabreen in northwest Svartisen. No evidence for any extensive glacial activity after the inlandice wastage approx. 9000 14C years B. P. and prior to 3000 14C years B.P. was forthcoming.

Major Neoglacial Glacier Expansion Episodes in Southern Norway: Evidences from Moraine Ridge Stratigraphy with 14 C Dates on Buried Palaeosols and Moss Layers

Major Neoglacial Glacier Expansion Episodes in Southern Norway: Evidences from Moraine Ridge Stratigraphy with 14 C Dates on Buried Palaeosols and Moss Layers

STUDIES ON SOME GLACIAL MORAINES IN NEW ZEALAND—2

Abstract The criteria (lichen measurements, geomorphology, vegetation cover and degree of weathering of rocks) used for comparing and dating moraine ridges near the Mueller, Tasman and Hooker glaciers at Mount Cook are briefly discussed. Characteristic land- forms, indicating that episodes of glacier expansion have occurred, include sharp- crested lateral moraines. A description is given of the chronology of moraine ridges formed by periods of expansion of the three glaciers during the last 700–800 years, illustrated by maps, diagrams and photographs. There have been marked expansions of one or more of the glaciers in A.D. mid 12th century, mid 13th century, mid 15th century, mid 16th century, early and mid-to-late 17th century, mid and late 18th century, early, mid, and late 19th century and about 1930. There may have been other minor expansions during this time span.