Little Ice Age Maximum Research Articles

Glacier fluctuations in extratropical South America during the past 1000 years

This paper presents an updated, extensive review of glacier fluctuations during the past 1000 years in the extratropical Andes of South America between ca. 17° and 55°S. Given the variety of environmental conditions and evidence available for glacier fluctuations across this wide latitudinal range, regional accounts are given for the Desert Andes (∼ 17°–31°S), the Andes of central Chile and Argentina (31°–36°S), and the North (36°–45°S) and South (45°–55°S) Patagonian Andes. The techniques, dating limitations, and interpretations of the glacier records along this transect are also discussed. Information on glacier fluctuations in the Desert Andes is limited to the 20th century. Documentation on past glacier variations is more abundant in the Central Chilean-Argentinean Andes, but the number of chronologies dealing with glacier fluctuations prior to the 1900s is also limited. Most records indicate that glaciers were generally more extensive prior to the 20th century, with dates of maximum expansion ranging from the 16th to the 19th centuries. The number and extent of glaciers increase significantly in the Patagonian region, where the evidence available for dating glacier variations during the past centuries is more abundant and the dating control for glacier events is generally better than in the northern parts of the study area. For some Patagonian glaciers, maximum Little Ice Age (LIA) or post-LIA advances have been precisely dated by dendro-geomorphological determinations or in situ measurements. However, for most sites, the evidence available is still preliminary and there is considerable variability in the extent and timing of events related to the maximum LIA expansion identified in most areas between the 16th and 19th centuries. Evidence is starting to appear at a growing number of sites for glacier advances during the first half of the past millennium. These events were generally less extensive than the LIA maximum pulses. Despite the occurrence of several post-LIA readvances over the past 100–110 years, most areas in the Andes of extratropical South America have experienced a general pattern of glacier recession and significant ice mass losses. The differences in the glacier histories observed at local and regional scales probably reflect the inherent limitations associated with the glacier records and/or the dating techniques used in each case together with the varying dominance of precipitation, temperature and other climatic and non-climatic factors on glacier mass balance and glacier dynamics. These differences indicate that the late Holocene glacier history of southern South America is more complex than commonly assumed. The evidence discussed in this study highlights not only the immense potential for glaciological studies of this region but also a significant need for an increased number of detailed, well-dated records of glacier fluctuations.

Asynchronous Little Ice Age glacial maximum extent in southeast Iceland

The Little Ice Age (LIA) maximum glacial extent of 13 glaciers located in SE Iceland was dated by lichenometry to check for intraregional variations. Different lichenometric approaches were applied to date maximum LIA moraines, and they all showed high variability between glaciers. According to the Extreme Value Theory and Bayesian approach, LIA advances in the region occurred in or around A.D. 1740–1760, A.D. 1810–1820 and A.D. 1840–1880 with confidence intervals of between 8 and 21 years. The dates were correlated with geomorphic characteristics of glacier tongues: hypsometric and slope parameters can be considered as determining factors in the variability of glacier timing during the LIA, as previously observed in Norway and in the Alps. In terms of timing, results obtained in SE Iceland were similar to those obtained for other glacier regions around the North Atlantic.

The reef builder gastropod Dendropomapetreaum – A proxy of short and long term climatic events in the Eastern Mediterranean

High-resolution δ 18O and δ 13C records obtained from seven cores were drilled from ledges of the reef builder gastropod Dendropoma petreaum and used to reconstruct variations in the Levantine basin sea surface temperature, hydrology and productivity during the past 500 years. The δ 18O of the aragonite shell of living D . petreaum indicate that skeletal deposition occurs under isotopic equilibrium and faithfully record the temperature and surface water δ 18O during summer and autumn. The mean down core δ 18O record clearly captures global and local climatic events, such as the Little Ice Age (LIA) and the recent warming of surface waters in the Eastern Mediterranean. Comparison to the Western Mediterranean vermetid δ 18O record reveals changes in the freshwater/evaporation budgets of the two basins during cold and warm periods. The Eastern basin had lower surface temperatures and excess evaporation during the LIA and experienced a relatively larger warming and/or a decrease in freshwater/evaporation during the past 70 years. The D . petraeum δ 13C is strongly related to δ 13C of dissolved inorganic carbon and to the primary productivity of the surface water. The mean down core δ 13C record exhibits enrichment during the LIA maximum and a strong depletion trend during the last century. The LIA δ 13C enrichment is attributed to an increase in primary production and high nutrient levels which resulted from increased vertical mixing and upwelling. The last century δ 13C depletion is mostly related to the increased anthropogenic emissions of 13C depleted carbon dioxide and to a certain decrease in primary production. The data indicate that D. petraeum isotopic signatures are unique proxies for last 500 years high-resolution reconstruction of paleo-oceanographic environments in the Mediterranean and potentially in the sub-tropical Atlantic regions.

Latest Pleistocene and Holocene glacier variations in the European Alps

In the Alps, climatic conditions reflected in glacier and rock glacier activity in the earliest Holocene show a strong affinity to conditions in the latest Pleistocene (Younger Dryas). Glacier advances in the Alps related to Younger Dryas cooling led to the deposition of Egesen stadial moraines. Egesen stadial moraines can be divided into three or in some cases even more phases (sub-stadials). Moraines of the earliest and most extended advance, the Egesen maximum, stabilized at 12.2 ± 1.0 ka based on 10Be exposure dating at the Schönferwall (Tyrol, Austria) and the Julier Pass-outer moraine (Switzerland). Final stabilization of moraines at the end of the Egesen stadial was at 11.3 ± 0.9 ka as shown by 10Be data from four sites across the Alps. From west to east the sites are Piano del Praiet (northwestern Italy), Grosser Aletschgletscher (central Switzerland), Julier Pass-inner moraine (eastern Switzerland), and Val Viola (northeastern Italy). There is excellent agreement of the 10Be ages from the four sites. In the earliest Holocene, glaciers in the northernmost mountain ranges advanced at around 10.8 ± 1.1 ka as shown by 10Be data from the Kartell site (northern Tyrol, Austria). In more sheltered, drier regions rock glacier activity dominated as shown, for example, at Julier Pass and Larstig valley (Tyrol, Austria). New 10Be dates presented here for two rock glaciers in Larstig valley indicate final stabilization no later than 10.5 ± 0.8 ka. Based on this data, we conclude the earliest Holocene (between 11.6 and about 10.5 ka) was still strongly affected by the cold climatic conditions of the Younger Dryas and the Preboreal oscillation, with the intervening warming phase having had the effect of rapid downwasting of Egesen glaciers. At or slightly before 10.5 ka rapid shrinkage of glaciers to a size smaller than their late 20th century size reflects markedly warmer and possibly also drier climate. Between about 10.5 ka and 3.3 ka conditions in the Alps were not conducive to significant glacier expansion except possibly during rare brief intervals. Past tree-line data from Kaunertal (Tyrol, Austria) in concert with radiocarbon and dendrochronologically dated wood fragments found recently in the glacier forefields in both the Swiss and Austrian Alps points to long periods during the Holocene when glaciers were smaller than they were during the late 20th century. Equilibrium line altitudes (ELA) were about 200 m higher than they are today and about 300 m higher in comparison to Little Ice Age (LIA) ELAs. The Larstig rock glacier site we dated with 10Be is the type area for a postulated mid-Holocene cold period called the Larstig oscillation (presumed age about 7.0 ka). Our data point to final stabilization of those rock glaciers in the earliest Holocene and not in the middle Holocene. The combined data indicate there was no time window in the middle Holocene long enough for rock glaciers of the size and at the elevation of the Larstig site to have formed. During the short infrequent cold oscillations between 10.5 and 3.3 ka small glaciers (less than several km 2) may have advanced to close to their LIA dimensions. Overall, the cold periods were just too short for large glaciers to advance. After 3.3 ka, climate conditions became generally colder and warm periods were brief and less frequent. Large glaciers (for example Grosser Aletschgletscher) advanced markedly at 3.0–2.6 ka, around 600 AD and during the LIA. Glaciers in the Alps attained their LIA maximum extents in the 14th, 17th, and 19th centuries, with most reaching their greatest LIA extent in the final 1850/1860 AD advance.

The Little Ice Age glacier advance in the Central Andes (35°S), Argentina

This paper documents the occurrence of the Little Ice Age (LIA) in the El Azufre and El Peñón glaciers at 35°S and in the Las Choicas and Las Damas glaciers at 34°55′S in the headwaters of the Rio Grande basin in the Central Andes of Argentina. Moraine morphology, stratigraphic relationships, radiocarbon ages obtained from peat on these glacial deposits and the proximity to the active glaciers enabled us to reconstruct the LIA advance in this area. The LIA maximum advance occurred between cal. yr 1550 and 1720 AD, and a readvance occurred around cal. yr 1830 AD. In addition, glacier fluctuations of the Las Vacas and Güssfeltd glaciers (33°S) and El Peñón and El Azufre glaciers were documented from the end of the 19th century to the present based on historical and aerial photographs, and satellite images. The glaciers showed a marked retreat during 1894–2007. Minor readvances occurred in the 1980s and 1990s, which could be related with strong warm ENSO events during these decades. Our results are consistent with observations made by other authors in the region.

Tree-ring crossdates for a First Millennium AD advance of Tebenkof Glacier, southern Alaska

Tree-ring crossdates from glacially killed logs show that Tebenkof Glacier advanced into a forefield forest in the AD 710s and 720s. Recession from this First Millennium AD (FMA) advance occurred before the 950s, after which the ice margin readvanced in the 1280s to 1320s at the start of the Little Ice Age (LIA). A more extensive LIA advance was underway from the 1640s to 1670s, and the terminus stayed at or near its LIA maximum until the 1890s. These are the first absolute tree-ring crossdates for a FMA glacier advance in North America and support growing evidence from northwestern North America and Europe for a significant cool interval in the centuries around AD 500.

Little Ice Age fluctuations of small glaciers in the Monte Fitz Roy and Lago del Desierto areas, south Patagonian Andes, Argentina

Current knowledge about late Holocene glacier fluctuations in the south Patagonian Andes is mainly based on evidence from large outlet glaciers of the North and South Patagonian Icefields, and few data exist for the smaller glaciers elsewhere in the region. Here we provide dendrogeomorphological evidence for Little Ice Age (LIA) and post-LIA activity for five small glaciers near the northeast margin of the South Patagonian Icefield. The study sites include Glaciar Torre and Piedras Blancas in the Monte Fitz Roy area, and three adjacent glaciers near Lago del Desierto. At these sites the LIA maximum position was identified by massive moraines with mature trees dating to the late 1500s–early 1600s. Several older moraines were observed beyond these limits but could not be precisely dated. Relatively synchronous advances occurred at most glaciers in the early 1700s and were dated using living trees and in situ, subfossil material. All glaciers show three to five subsequent advances mostly concentrated between the mid-19th and early 20th centuries. Estimates based on Landsat TM imagery indicate these glaciers lost between 15 and 46% of their LIA areas by 1984 and a further 5–18% by 2005, with the smallest glaciers showing the greatest proportional loss. Paired comparisons of contemporary and the earliest known photography for the glaciers in the Fitz Roy area confirm this mass loss. These results provide important new information on the glacier history of this area but additional, more precisely-dated records are needed from many more sites before we can fully elucidate the complex late Holocene glacial history of this region.

Sediment magnetic properties of glacial till deposited since the Little Ice Age maximum for selected glaciers at Svartisen and Okstindan, northern Norway

Samples of glacial till deposited since the Little Ice Age (LIA) maximum by two glaciers, North Bogbre at Svartisen and Corneliussen-breen at Okstindan, northern Norway, were obtained from transects running from the current glacier snout to the LIA (c. AD 1750) limit. The samples were analysed to determine their sediment magnetic properties, which display considerable variability. Significant trends in some magnetic parameters are evident with distance from the glacier margin and hence length of subaerial exposure. Magnetic susceptibility (X) decreases away from the contemporary snout, perhaps due to the weathering of ferrimagnetic minerals into antiferromagnetic forms, although this trend is generally not statistically significant. Trends in the ratios of soft IRM/hard IRM which are statistically significant support this hypothesis, suggesting that antiferromagnetic minerals are increasing relative to ferrimagnetic minerals towards the LIA maximum. Backfield ratios (IRM -100 mT/SIRM) also display a significant and strong trend towards magnetically harder behaviour with proximity to the LIA maximum. Thus, by employing a chronosequence approach, it may be possible to use sediment magnetics data as a tool for reconstructing glacier retreat in areas where more traditional techniques, such as lichenometry, are not applicable.

Holocene climate inferred from glacier extent, lake sediment and tree rings at Goat Lake, Kenai Mountains, Alaska, USA

AbstractLake sediment, glacier extent and tree rings were used to reconstruct Holocene climate changes from Goat Lake at 550 m asl in the Kenai Mountains, south‐central Alaska. Radiocarbon‐dated sediment cores taken at 55 m water depth show glacial‐lacustrine conditions until about 9500 cal. yr BP, followed by organic‐rich sedimentation with an overall increasing trend in organic matter and biogenic silica content leading up to the Little Ice Age (LIA). Through most of the Holocene, the northern outlet of the Harding Icefield remained below the drainage divide that currently separates it from Goat Lake. A sharp transition from gyttja to inorganic mud about AD 1660 signifies the reappearance of glacier meltwater into Goat Lake during the LIA, marking the maximum Holocene (postglacial) extent. Meltwater continued to discharge into the lake until about AD 1900. A 207 yr tree‐ring series from 25 mountain hemlocks growing in the Goat Lake watershed correlates with other regional tree‐ring series that indicate an average summer temperature reduction of about 1°C during the 19th century compared with the early–mid 20th century. Cirque glaciers around Goat Lake reached their maximum LIA extent in the late 19th century. Assuming that glacier equilibrium‐line altitudes (ELA) are controlled solely by summer temperature, then the cooling of 1°C combined with the local environmental lapse rate would indicate an ELA lowering of 170 m. In contrast, reconstructed ELAs of 12 cirque glaciers near Goat Lake average only 34 ± 18 m lower during the LIA. The restricted ELA lowering can be explained by a reduction in accumulation‐season precipitation caused by a weakening of the Aleutian low‐pressure system during the late LIA. Copyright © 2008 John Wiley & Sons, Ltd.

Little Ice Age and neoglacial landforms at the Inland Ice margin, Isunguata Sermia, Kangerlussuaq, west Greenland

Neoglacial and Little Ice Age (LIA) limits occur within 2km of the Inland Ice margin in the Kangerlussuaq area on west Greenland. The LIA limit is clearly demarcated by ice‐cored and non‐ice‐cored moraines, out‐wash surfaces and trimlines. Rhizocarpon sp. thalli of ≥16mm on these landforms indicate a 1‐2km retreat of the Inland Ice in the past c. 100 years, coincident with peripheral thinning of the ice. An older neoglacial moraine host of Rhizocarpon sp. thalli <40 mm indicates a minimum limiting age of <400 BP, whereas Optically Stimulated Luminescence (OSL) ages on aeolian silt capping the moraine yield close limiting ages of c. 2000 BP. Aeolian silt deposition beyond neoglacial limits yields OSL ages of c. 3000 BP, potentially coeval with advance of the Inland Ice. Aeolian sedimentation and the inferred age of the moraine are coincident with pronounced cooling inferred from palaeolimnological records from west and south Greenland. This neoglacial event at c. 2000 BP is probably of similar extent to the LIA maximum, because of the paucity of preserved moraine remnants.

Recalibration of the yellow Rhizocarpon growth curve in the Cordillera Blanca (Peru) and implications for LIA chronology

A new lichen dating method and new moraine observations enabled us to improve the chronology of glacier advances in the Cordillera Blanca (Peru) during the Little Ice Age (LIA). Our results reveal that an early LIA glacial advance occurred around AD 1330 ± 29. However, a second major glacial advance at the beginning of the 17th century overlapped the earlier stage for most glaciers. Hence, this second glacial stage, dated from AD 1630 ± 27, is considered as the LIA maximum glacial advance in the Cordillera Blanca. During the 17th–18th centuries, at least three glacial advances were recorded synchronously for the different glaciers (AD 1670 ± 24, 1730 ± 21, and 1760 ± 19). The moraines corresponding to the two first stages are close to the one in 1630 suggesting a slow recession of about 18% in the total length of the glacier. From the LIA maximum extent to the beginning of the 20th century, the 24 glaciers have retreated a distance of about 1000 m, corresponding to a reduction of 30% in their length. This rate is comparable to that observed during the 20th century. Estimates of palaeo-Equilibrium Line Altitudes show an increase in altitude of about 100 m from the LIA maximum glacial extension at the beginning of the 17th century to the beginning of the 20th century. Because long time series are not available for precipitation and temperature, this glacial retreat is difficult to explain by past climate changes. However, there is a fair correspondence between changes in glacier length and the δ 18O recorded in the Quelccaya ice core at a century timescale. Our current knowledge of tropical glaciers and isotope variations leads us to suggest that this common tropical signal reflects a change from a wet LIA to the drier conditions of today. Finally, a remarkable synchronicity is observed with glacial variations in Bolivia, suggesting a common regional climatic pattern during the LIA.

Glacier recession on Cerro Charquini (16° S), Bolivia, since the maximum of the Little Ice Age (17th century)

AbstractCerro Charquini, Bolivia (Cordillera Real, 5392 ma.s.l.) was selected as a site to reconstruct glacier recession since the maximum of the Little Ice Age (LIA) in the central Andes. Five glaciers, located on differently exposed slopes, present comprehensive and well-preserved morainic systems attributed to former centuries. The moraines were dated by lichenometry and show a consistent organization on the different slopes. The past geometry of the glaciers was reconstructed using ground topography and aerophotogrammetry. Lichenometric dating shows that the LIA maximum occurred in the second half of the 17th century, after which the glaciers have receded nearly continuously. Over the last decades of the 20th century (1983–97), recession rates increased by a factor of four. On the northern and western slopes, glaciers receded more than on the southern and eastern slopes (by 78% and 65% of their LIA maximum area, respectively). The mean equilibrium-line altitude (ELA) rose by about 160 m between the LIA maximum and 1997. Recession rates were analysed in terms of climatic signal, suggesting that glacier recession since the LIA maximum was mainly due to a change in precipitation and that the 19th century may have been drier. For the 20th century, a temperature rise of about 0.6°C appears to be the main cause of glacier recession. Recent climatic conditions from 1983 to 1997 correspond to a mass deficit of about 1.36m w.e.a–1. If such conditions persist, the small glaciers below 5300ma.s.l. in the Cordillera Real should disappear completely in the near future.

A revised chronology of key Vatnajökull (Iceland) outlet glaciers during the Little Ice Age

AbstractGlacier fluctuations from key Vatnajökull outlets have been redated using tephrochronology coupled with two lichenometric techniques to ascertain the timing of the Little Ice Age (LIA) maximum in southeast Iceland. An updated tephrochronology for southeast Iceland (both the number of tephra layers present and their geochemical signatures) indicates a LIA maximum for both glaciers between AD 1755 and 1873. Based on a population gradient approach, lichenometrically dated moraines along the margins of Skálafellsjökull and Heinabergsjökull narrow this window to the early to mid-19th century respectively. These revised chronologies, in addition to emerging evidence from elsewhere in Iceland, support a late 18th- to early 19th-century LIA glacier maximum. In contrast, the Norwegian LIA glacial maximum is strongly centred around AD1750. This implies differing glaciological responses to secular shifts in the North Atlantic Oscillation. Such revisions to the Vatnajökull record are crucial, as accurately identifying the timing and delimiting the spatial extent of the Icelandic LIA glacier maximum will allow further light to be shed on glacier–climate interactions in the North Atlantic.

Re‐dating the moraines at skálafellsjökull and heinabergsjökull using different lichenometric methods: implications for the timing of the icelandic little ice age maximum

Little Ice Age (LIA) moraines along the margins of Skálafellsjökull and Heinabergsjökull, two neighbouring outlet glaciers flowing from the Vatnajökull ice‐cap, have been re‐dated to test the reliability of different lichenometric approaches. During 2003, 12 000 lichens were measured on 40 moraine fragments at Skálafellsjökull and Heinabergsjökull to provide surface age proxies. The results are revealing. Depending on the chosen method of analysis, Skálafellsjökull either reached its LIA maximum in the early 19th century (population gradient) or the late 19th century (average of five largest lichens), whereas the LIA maximum of Heinabergsjökull occurred by the mid‐19th century (population gradient) or late‐19th century (average of 5 largest lichens). Discrepancies (c. 80 years for Skálafellsjökull and c. 40 years for Heinabergsjökull) suggest that the previously cited AD 1887 LIA maxima for both glaciers should be reassessed. Dates predicted by the lichen population gradient method appear to be the most appropriate, as mounting evidence from other geochronological reconstructions and sea‐ice records throughout Iceland tends to support an earlier LIA glacier maximum (late 18th to mid‐19th century) and probably reflects changes in the North Atlantic Oscillation. These revised chronologies shed further light on the precise timing of the Icelandic LIA glacier maximum, whilst improving our understanding of glacier‐climate interactions in the North Atlantic.

A revised Little Ice Age chronology of the Franz Josef Glacier, Westland, New Zealand

A reassessed Little Ice Age chronology of the Franz Josef Glacier is presented. Diameter at breast height of 1340 southern rata (Metrosideros umbellata) and kamahi (Weinmannia racemosa) was measured within 50, 150‐m2 quadrats in the Waiho Valley. Age‐size relationships based on 60 tree‐ring counts and associated diameter at breast height measurements were constructed, although the unknown shape of growth curves beyond the realm of tree‐ring data rendered extrapolation unreliable. Thus, the revised chronology is interpreted from mapped tree‐ring counts and measured diameter at breast height of the largest rata and kamahi within moraine limits and trimlines to determine the minimum time elapsed since deglaciation. The Franz Josef Glacier's Little Ice Age (LIA) maximum culminated before AD 1600, when it terminated c. 4.5 km down‐valley of its 2001 position. Subsequent, but lesser magnitude, re‐advances culminated by c. AD 1600 and 1800. This pattern is strongly corroborated by other New Zealand proxy climate data. Evidence from this reassessment provides increasing support for an earlier LIA maximum of the Franz Josef Glacier than is often cited.

The retreat of tien shan glaciers (kyrgyzstan) since the little ice age estimated from aerial photographs, lichenometric and historical data

The retreat of 293 glaciers in the Tien Shan Mountains (Kyrgyz Republic) from their maximum extent during the Little Ice Age (LIA) is estimated using aerial photographs from 1980 to 1985 and maps at a scale of 1:25000, constructed during period 1956–1990. Two indices of changes are used: the linear distance from the glacier terminus to its Little Ice Age moraine and the difference in absolute elevation of the terminus and the moraine. Historical information about the front positions of glaciers in the 1880s to the 1930s was used as an indirect control of remote sensing data. The age of moraines in key regions was estimated by lichenometry. On average, Tien Shan glaciers have retreated by 989 ± 540 m since the LIA maximum. Their front elevations (dh) rose by 151 ± 105 m. These changes are similar to changes observed in the Alps and western Norway, Pamir‐Alay and Koryak plateau, but greater than in east Siberia over the same interval. Differences between four regions in Tien Shan (northern, western, inner, central) are generally small, though in the northern Tien Shan the glacier retreat and frontal rise are more prominent (1065 ± 479 m and 215 ± 140 m, respectively).

The evidence for paraglacial sedimentation and its temporal scale in the deglacierizing basin of Small River Glacier, Canada

Spatially sampled suspended sediment data from extra-channel surfaces of different ages during rainfall events were used to infer the timescale of landscape adjustment to Little Ice Age (LIA) deglacierization at Small River Glacier, Canada. Surface ages were determined by aerial photograph interpretation. Turbidimeters were installed in three ephemeral channels on “young,” “mature” and “old” surfaces; and their response to rainfall events of different magnitudes recorded. Results showed “young” ice proximal surfaces exposed since 1977 were increasingly vulnerable to mobilization during rainfall events. A suspended sediment response from “old” surfaces exposed since 1910 was recorded for only three events with ∼5- and 30-year return periods. The intensity and duration of rainfall events therefore had to increase in magnitude to mobilize sediment on surfaces of increasing maturity. Hysteresis in the channel suspended sediment response further confirmed the dependence of surface response on rainfall event magnitude. The rapid temporal decline in surface response indicated that surface armoring or sediment exhaustion is stabilizing surfaces within decades of exposure from the LIA maximum (ca. 1910) at Small River Glacier. However, further perturbation, for example by glacial advance or extreme climatic events, would likely modify the pattern of suspended sediment yields by changing terrain surface mobilization thresholds and reconfiguring channel sediment stores. We therefore suggest that it is difficult to determine when “paraglacial sedimentation” ceases to influence suspended sediment yields, and therefore significantly limiting the usefulness of the term to describe the period of suspended sediment yield adjustment following deglacierization.

The Climate of Little Ice Age Maximum in China

小冰期是距今最近的全球性冷气候事件,是至今研究历史时期气候与人类活动关系的重点时期,它曾对世界和我国的社会经济产生了重要影响. 本文根据我国近年来历史文献、冰芯、树轮、湖芯和石笋的高分辨率研究成果,结合部分国外的结果,对小冰期从高纬、高山地区向中纬、低海拔地区的发展过程,17世纪小冰期盛期大范围普遍的降温、降水变化和空间分布与季风的关系进行了讨论. 该成果和气候模拟的结果可进行检验,为全球增温背景上可能出现的冷波动提供历史相似型.;Little Ice Age (LIA) is the global cold event nearest to modern time, having an important effect on the development of society and economy throughout the world and in China. As a key period, it is now being used to explore the relationship between historical climate and human activity. Based on historical documents and the result of high resolution proxies (ice core, tree-ring, lake sediment, stalagmite) in recent years, incorporating with part of the foreign researches, several characteristics of LIA are discussed in this paper, including the climatic evolutional process from high-latitude and high-altitude regions to mid-latitude and low-altitude regions and how the monsoon influences the universal temperature decrease of wide range in 17th century, the maximum of LIA, and the variation and distribution of precipitation. By verifying the climate simulations with these results, palaeo-analogue can be obtained to predict the cold oscillation in the global warming background.

Glacier changes since the Little Ice Age maximum in the western Qilian Shan, northwest China, and consequences of glacier runoff for water supply

AbstractBased on aerial photographs, topographical maps and the Landsat-5 image data, we have analyzed fluctuations of glaciers in the western Qilian Shan, north-west China, from the Little Ice Age (LIA) to 1990. The areas and volumes of glaciers in the whole considered region decreased 15% and 18%, respectively, from the LIA maximum to 1956. This trend of glacier shrinkage continued and accelerated between 1956 and 1990. These latest decreases in area and volume were about 10% in 34 years. The recent shrinkage may be due either to a combination of higher temperatures and lower precipitation during the period 1956–66, or to continuous warming in the high glacierized mountains from 1956 to 1990. As a consequence, glacier runoff from ice wastage between 1956 and 1990 has increased river runoff by 6.2 km3 in the four river basins under consideration. Besides, the equilibrium-line altitude (ELA) rise estimated from the mean terminus retreat of small glaciers <1 km long is 46 m, which corresponds to a 0.3°C increase of mean temperatures in warm seasons from the LIA to the 1950s.