scholarly journals Palynological evidence from a sub-alpine marsh of enhanced Little Ice Age snowpack in the Marrakech High Atlas, North Africa

2021 ◽  
Author(s):  
Benjamin A. Bell ◽  
William J. Fletcher ◽  
Philip D. Hughes ◽  
Henk L. Cornelissen ◽  
David Fink ◽  
...  
Keyword(s):  
20Th Century ◽  
Little Ice Age ◽  
Management Practices ◽  
Accumulation Point ◽  
Ice Age ◽  
Pollen Record ◽  
Climatic Fluctuations ◽  
Radiocarbon Dates ◽  
High Atlas ◽  
Grazing Impacts

AbstractThe grazing lands of the High Atlas are vulnerable to climate change and the decline of traditional management practices. However, prior to the mid-20th century, there is little information to examine historical environmental change and resilience to past climate variability. Here, we present a new pollen, non-pollen palynomorph (NPP) and microcharcoal record from a sub-alpine marsh (pozzine) at Oukaïmeden, located in the Marrakech High Atlas, Morocco. The record reveals a history of grazing impacts with diverse non-arboreal pollen assemblages dominant throughout the record as well as recurrent shifts between wetter and drier conditions. A large suite of radiocarbon dates (n = 22) constrains the deposit to the last ~ 1,000 years although multiple reversed ages preclude development of a robust age-depth model for all intervals. Between relatively dry conditions during the Medieval period and in the 20th century, intervening wet conditions are observed, which we interpret as a locally enhanced snowpack during the Little Ice Age. Hydrological fluctuations evidenced by wetland pollen and NPPs are possibly associated with centennial-scale precipitation variability evidenced in regional speleothem records. The pollen record reveals an herbaceous grassland flora resilient against climatic fluctuations through the last millennium, possibly supported by sustainable collective management practices (agdal), with grazing indicators suggesting a flourishing pastoral economy. However, during the 20th century, floristic changes and increases in charcoal accumulation point to a decline in management practices, diversification of land-use (including afforestation) and intensification of human activity.

A High-Resolution 11,400-Yr Diatom Record from Lake Victoria, East Africa

1997 ◽  
Vol 47 (1) ◽  
pp. 81-89 ◽  
Author(s):  
J.Curt Stager ◽  
Brian Cumming ◽  
Loren Meeker
Keyword(s):  
Little Ice Age ◽  
Lake Victoria ◽  
Ice Age ◽  
Pollen Record ◽  
Diatom Assemblages ◽  
Climatic Fluctuations ◽  
The Past ◽  
Phytoplankton Communities ◽  
Abrupt Changes ◽  
Globally Distributed

AbstractFine-interval (∼30–45 yr) sampling of a core from Lake Victoria's Damba Channel shows that numerous abrupt changes in the lake's diatom assemblages have occurred in response to climatic fluctuations over the past 11,40014C yr. Four distinct climatic phases bounded by sudden transitions are inferred: (1) variably dry ∼11,400–10,000 yr B.P., (2) humid ∼10,000–7200 yr B.P., (3) more seasonal ∼7200–2200 yr B.P., and (4) more arid ∼2200–0 yr B.P., with a dry “Little Ice Age” event ∼600–200 yr B.P. The diatom-inferred paleoclimatic history for northern Lake Victoria closely resembles that inferred from a well-dated pollen record from Pilkington Bay. Spectral analysis of the diatom record reveals strong periodicities including globally distributed ∼2360–2550, ∼1400, ∼1030–1130, and ∼500 cal-yr cycles. Repeated, rapid shifts betweenAulacoseira- andNitzschia-dominated diatom assemblages suggest that post-1960 changes in the lake's phytoplankton communities have had earlier, climate-driven analogs.

scholarly journals Three Millennia of Vegetation, Land-Use and Climate Change in SE Sicily

Forests ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 102
Author(s):  
Fabrizio Michelangeli ◽  
Federico Di Di Rita ◽  
Alessandra Celant ◽  
Nadine Tisnérat-Laborde ◽  
Fabrizio Lirer ◽  
...  
Keyword(s):  
Land Use ◽  
Little Ice Age ◽  
Forest Recovery ◽  
Ice Age ◽  
Tree Cover ◽  
Pollen Record ◽  
Primary Role ◽  
Climatic Fluctuations ◽  
South Central ◽  
Land Use Practices

This study presents the first Late Holocene marine pollen record (core ND2) from SE Sicily. It encompasses the last 3000 years and is one of the most detailed records of the south-central Mediterranean region in terms of time resolution. The combined approach of marine palynology and historical ecology, supported by independent palaeoclimate proxies, provides an integrated regional reconstruction of past vegetational dynamics in relation to rapid climatic fluctuations, historical socio-economic processes, and past land-use practices, offering new insights into the vegetation history of SE Sicily. Short-term variations of sparse tree cover in persistently open landscapes reflect rapid hydroclimatic changes and historical land-use practices. Four main phases of forest reduction are found in relation to the 2.8 ka BP event, including the Late Antique Little Ice Age, the Medieval Climate Anomaly, and the Little Ice Age, respectively. Forest recovery is recorded during the Hellenistic and Roman Republican Periods, the Early Middle Ages, and the last century. Agricultural and silvicultural practices, as well as stock-breeding activities, had a primary role in shaping the current vegetational landscape of SE Sicily.

Ice-Core Pollen Record of Climatic Changes in the Central Andes during the last 400 yr

2005 ◽  
Vol 64 (2) ◽  
pp. 272-278 ◽  
Author(s):  
Kam-biu Liu ◽  
Carl A. Reese ◽  
Lonnie G. Thompson
Keyword(s):  
Little Ice Age ◽  
Ice Core ◽  
Climatic Changes ◽  
Ice Age ◽  
Striking Similarity ◽  
Pollen Record ◽  
Dry Period ◽  
Proxy Records ◽  
Ice Cap ◽  
Ice Accumulation

AbstractThis paper presents a high-resolution ice-core pollen record from the Sajama Ice Cap, Bolivia, that spans the last 400 yr. The pollen record corroborates the oxygen isotopic and ice accumulation records from the Quelccaya Ice Cap and supports the scenario that the Little Ice Age (LIA) consisted of two distinct phases�"a wet period from AD 1500 to 1700, and a dry period from AD 1700 to 1880. During the dry period xerophytic shrubs expanded to replace puna grasses on the Altiplano, as suggested by a dramatic drop in the Poaceae/Asteraceae (P/A) pollen ratio. The environment around Sajama was probably similar to the desert-like shrublands of the Southern Bolivian Highlands and western Andean slopes today. The striking similarity between the Sajama and Quelccaya proxy records suggests that climatic changes during the Little Ice Age occurred synchronously across the Altiplano.

scholarly journals Relation between recent glacier variations and climate in the Tien Shan mountains, central Asia

1992 ◽  
Vol 16 ◽  
pp. 11-16 ◽  
Author(s):  
Liu Chaohai ◽  
Han Tianding
Keyword(s):  
Mass Balance ◽  
Central Asia ◽  
Air Temperature ◽  
Little Ice Age ◽  
General Trend ◽  
Summer Temperature ◽  
Tien Shan ◽  
Ice Age ◽  
Climatic Fluctuations ◽  
Tien Shan Mountains

Since the Little Ice Age, most glaciers in the Tien Shan mountains have been retreating. Owing to an increase in precipitation in most parts of the mountains during the late 1950s to early 1970s, the percentage of receding glaciers and the speed of retreat have tended to decrease in the 1970s. However, the general trend of continuous glacier retreat remains unchanged, in part because the summer air temperature shows no tendency to decrease.In the Tien Shan mountains, as the degree of climatic continentality increases the mass balance becomes more dependent on summer temperature, and accumulation and ablation tend to be lower. Therefore, the responses of glaciers to climatic fluctuations in more continental areas are not synchronous with those in less continental areas, and the amplitude of the glacier variations becomes smaller.

Holocene Glacial and Tree-Line Variations in the White River Valley and Skolai Pass, Alaska and Yukon Territory

1977 ◽  
Vol 7 (1) ◽  
pp. 63-111 ◽  
Author(s):  
George H. Denton ◽  
Wibjörn Karlén
Keyword(s):  
20Th Century ◽  
Little Ice Age ◽  
Yukon Territory ◽  
Summer Temperature ◽  
River Valley ◽  
Ice Age ◽  
The Arctic ◽  
Tree Line ◽  
White River ◽  
Glacier Recession

Complex glacier and tree-line fluctuations in the White River valley on the northern flank of the St. Elias and Wrangell Mountains in southern Alaska and Yukon Territory are recognized by detailed moraine maps and drift stratigraphy, and are dated by dendrochronology, lichenometry,14C ages, and stratigraphic relations of drift to the eastern (123014C yr BP) and northern (198014C yr BP) lobes of the White River Ash. The results show two major intervals of expansion, one concurrent with the well-known and widespread Little Ice Age and the other dated between 2900 and 210014C yr BP, with a culmination about 2600 and 280014C yr BP. Here, the ages of Little Ice Age moraines suggest fluctuating glacier expansion between ad 1500 and the early 20th century. Much of the 20th century has experienced glacier recession, but probably it would be premature to declare the Little Ice Age over. The complex moraine systems of the older expansion interval lie immediately downvalley from Little Ice Age moraines, suggesting that the two expansion intervals represent similar events in the Holocene, and hence that the Little Ice Age is not unique. Another very short-lived advance occurred about 1230 to 105014C yr BP. Spruce immigrated into the valley to a minimum altitude of 3500 ft (1067 m), about 600 ft (183 m) below the current spruce tree line of 4100 ft (1250 m), at least by 802014C yr BP. Subsequent intervals of high tree line were in accord with glacier recession; in fact, several spruce-wood deposits above current tree line occur bedded between Holocene tills. High deposits of fossil wood range up to 76 m above present tree line and are dated at about 5250, 3600 to 3000, and 2100 to 123014C yr BP. St. Elias glacial and tree-line fluctuations, which probably are controlled predominantly by summer temperature and by length of the growing and ablation seasons, correlate closely with a detailed Holocene tree-ring curve from California, suggesting a degree of synchronism of Holocene summer-temperature changes between the two areas. This synchronism is strengthened by comparison with the glacier record from British Columbia and Mt. Rainier. Likewise, broad synchronism of Holocene events exists across the Arctic between the St. Elias Mountains and Swedish Lappland. Finally, two sequences from the Southern Hemisphere show similar records, in so far as dating allows. Hence, we believe that a preliminary case can be made for broad synchronism of Holocene climatic fluctuations in several regions, although further data are needed and several areas, particularly Colorado and Baffin Island, show major differences in the regional pattern.

Pattern and Forcing of Northern Hemisphere Glacier Variations During the Last Millennium

1986 ◽  
Vol 26 (1) ◽  
pp. 27-48 ◽  
Author(s):  
Stephen C. Porter
Keyword(s):  
Northern Hemisphere ◽  
Little Ice Age ◽  
Ice Core ◽  
Volcanic Eruptions ◽  
Ice Age ◽  
Phase Lag ◽  
Mountain Glacier ◽  
Radiocarbon Dates ◽  
Glacier Fluctuations ◽  
Decadal Scale

Time series depicting mountain glacier fluctuations in the Alps display generally similar patterns over the last two centuries, as do chronologies of glacier variations for the same interval from elsewhere in the Northern Hemisphere. Episodes of glacier advance consistently are associated with intervals of high average volcanic aerosol production, as inferred from acidity variations in a Greenland ice core. Advances occur whenever acidity levels rise sharply from background values to reach concentrations ≥1.2 μequiv H+/kg above background. A phase lag of about 10–15 yr, equivalent to reported response lags of Alpine glacier termini, separates the beginning of acidity increases from the beginning of subsequent ice advances. A similar relationship, but based on limited and less-reliable historical data and on lichenometric ages, is found for the preceding 2 centuries. Calibrated radiocarbon dates related to advances of non-calving and non-surging glaciers during the earlier part of the Little Ice Age display a comparable consistent pattern. An interval of reduced acidity values between about 1090 and 1230 A.D. correlates with a time of inferred glacier contraction during the Medieval Optimum. The observed close relation between Noothern Hemisphere glacier fluctuations and variations in Greenland ice-core acidity suggests that sulfur-rich aerosols generated by volcanic eruptions are a primary forcing mechanism of glacier fluctuations, and therefore of climate, on a decadal scale. The amount of surface cooling attributable to individual large eruptions or to episodes of eruptions is simlar to the probable average temperature reduction during culminations of Little Ice Age alacier advances (ca. 0.5°–1.2°C), as inferred from depression of equilibrium-line altitudes.

Late Glacial and Late Holocene Moraines in the Cerros Cuchpanga, Central Peru

1984 ◽  
Vol 21 (3) ◽  
pp. 275-285 ◽  
Author(s):  
H.E. Wright
Keyword(s):  
Little Ice Age ◽  
Late Holocene ◽  
Late Glacial ◽  
Ice Age ◽  
Recent Past ◽  
Valley Bottom ◽  
Radiocarbon Dates ◽  
Western Cordillera ◽  
Limestone Bedrock ◽  
Ice Field

Small ice fields on the western cordillera northeast of Lima were expanded to three times their present size in the recent past, and the regional snow line was probably about 100 m lower than it is today. Outwash from the expanded glaciers formed deltas of silt in valley-bottom lakes. When the ice lobes retreated, the reduced outwash was trapped behind recessional moraines, and the clear meltwater infiltrated into the limestone bedrock and emerged at the heads of the deltas in spring pools. The delta surfaces then became covered with peat, and radiocarbon dates for the base of the peat (1100 ± 70 and 430 ± 70 yr B.P. for two different deltas) indicate that the maximum ice advance was older than those dates and, thus, older than the Little Ice Age of many north-temperate regions. Much older moraines date from expansion of the same local summit glaciers to even lower levels in the main valleys, which had previously been inundated by the cordilleran ice field. The cordilleran deglaciation and this expansion of local glaciers probably occurred between 12,000 and 10,000 yr ago, on the basis of slightly contradictory radiocarbon dates.

scholarly journals Moisture Changes in the Northern Xinjiang Basin Over the Past 2400 years as Documented in Pollen Records of Jili Lake

2021 ◽  
Vol 9 ◽  
Author(s):  
Yulin Xiao ◽  
Lixiong Xiang ◽  
Xiaozhong Huang ◽  
Keely Mills ◽  
Jun Zhang ◽  
...  
Keyword(s):  
Little Ice Age ◽  
Terrestrial Ecosystem ◽  
Warm Period ◽  
Ice Age ◽  
Pollen Record ◽  
Humid Climate ◽  
Northern Xinjiang ◽  
The Past ◽  
Climate Background

Regional humidity is important for terrestrial ecosystem development, while it differs from region to region in inland Asia, knowledge of past moisture changes in the lower basin of northern Xinjiang remainly largely unclear. Based on a pollen record from Jili Lake, the Artemisia/(Amaranthaceae + Ephedra) (Ar/(Am + E)) ratio, as an index of regional humidity, has recorded four relatively dry phases: 1) 400 BCE to 1 CE, 2) the Roman Warm Period (RWP; c. 1–400 CE), 3) the Medieval Warm Period (MWP; c. 850–1200 CE) and 4) the Current Warm Period (CWP; since 1850 CE). In contrast, the Dark Age Cold Period (DACP; c. 400–850 CE) and the Little Ice Age (LIA; c. 1200–1850 CE) were relatively wet. Lower lake levels in a relatively humid climate background indicated by higher aquatic pollen (Typha and Sparganium) after c. 1700 CE are likely the result of intensified irrigation for agriculture in the catchment as documented in historical records. The pollen Ar/(Am + E) ratio also recorded a millennial-scale wetting trend from 1 CE to 1550 CE which is concomitant with a long-term cooling recorded in the Northern Hemisphere.

scholarly journals Morphogenesis of New Straits and Islands Originated in the European Arctic Since the 1980s

Geosciences ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 476
Author(s):  
Wieslaw Ziaja ◽  
Krzysztof Ostafin
Keyword(s):  
20Th Century ◽  
Little Ice Age ◽  
Satellite Images ◽  
Ice Age ◽  
Climate Conditions ◽  
Main Research ◽  
Franz Josef Land ◽  
European Arctic ◽  
In The Beginning ◽  
Origin Analysis

Several new islands and many islets have appeared in the European Arctic since the end of the 20th century due to glacial recession under climate warming. The specificity of the formation of each individual strait and island is shown in the paper (apart from its location and timing of its origin). Analysis of available maps and satellite images of all three European Arctic archipelagos, from different times since 1909–1910, was the main research method. There are three pathways of the morphogenesis of the new islands: (1) simultaneous recession of glaciers from both sides of a depression in bedrock being a potential strait (typical in Franz Josef Land), (2) uncovering a rocky hill (which protrudes from a depression in bedrock) from under a receding glacier, (3) recession of one glacier which had reached a rocky fragment of a coastline (e.g., headland or peninsula), being a potential new island, during a maximum extent of this glacier during the Little Ice Age (in the beginning of the 20th century). Additional straits and islands are currently at the stage of formation and will continue to form in the European Arctic in the case of further warming or stabilization of the current climate conditions.

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