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 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 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.

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.

Glacier fluctuations during the past millennium in Garibaldi Provincial Park, southern Coast Mountains, British Columbia

2007 ◽  
Vol 44 (9) ◽  
pp. 1215-1233 ◽  
Author(s):  
Johannes Koch ◽  
John J Clague ◽  
Gerald D Osborn
Keyword(s):  
British Columbia ◽  
Little Ice Age ◽  
Ice Age ◽  
Southern Coast ◽  
Coast Mountains ◽  
The Past ◽  
Glacier Fluctuations ◽  
Garibaldi Provincial Park ◽  
Provincial Park ◽  
Past Millennium

The Little Ice Age glacier history in Garibaldi Provincial Park (southern Coast Mountains, British Columbia) was reconstructed using geomorphic mapping, radiocarbon ages on fossil wood in glacier forefields, dendrochronology, and lichenometry. The Little Ice Age began in the 11th century. Glaciers reached their first maximum of the past millennium in the 12th century. They were only slightly more extensive than today in the 13th century, but advanced at least twice in the 14th and 15th centuries to near their maximum Little Ice Age positions. Glaciers probably fluctuated around these advanced positions from the 15th century to the beginning of the 18th century. They achieved their greatest extent between A.D. 1690 and 1720. Moraines were deposited at positions beyond present-day ice limits throughout the 19th and early 20th centuries. Glacier fluctuations appear to be synchronous throughout Garibaldi Park. This chronology agrees well with similar records from other mountain ranges and with reconstructed Northern Hemisphere temperature series, indicating global forcing of glacier fluctuations in the past millennium. It also corresponds with sunspot minima, indicating that solar irradiance plays an important role in late Holocene climate change.

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.

Humidity variations spanning the ‘Little Ice Age’ from an upland lake in southwestern China

The Holocene ◽  
2019 ◽  
Vol 30 (2) ◽  
pp. 289-299
Author(s):  
Tingwei Zhang ◽  
Xiaoqiang Yang ◽  
Qiong Chen ◽  
Jaime L Toney ◽  
Qixian Zhou ◽  
...  
Keyword(s):  
Little Ice Age ◽  
Asian Monsoon ◽  
Activity Index ◽  
Ice Age ◽  
Western China ◽  
Southwestern China ◽  
Sunspot Activity ◽  
Precipitation Pattern ◽  
The Past ◽  
Westerly Jet

A number of archives that span the past ~2000 years suggest that recent variability in hydroclimatic conditions that are influenced by the Asian monsoon in China are unusual in the longer term context. However, the lack of high-resolution precipitation records over this period hampered our ability to characterize and constrain the forcing mechanism(s) of the recent humidity variations. Here, we present the ratio of hematite to goethite (Hm/Gt) derived from the semiquantitative evaluation of the diffuse reflectance spectroscopic analysis as a reliable and effective precipitation proxy to reconstruct the humidity variations during the past 1400 years deduced from Tengchongqinghai Lake sediments, southwestern China. Hm/Gt varied synchronously with variations of Chinese temperature reconstructed from the historical documents and sunspot activity index over the past 1400 years. Critical periodicities of ~450 and ~250 years show that solar activity is the dominant control on precipitation change on centennial scales. However, the relationship determined from Hm/Gt in this study contradicts the stalagmite δ18O interpretations from different regions of China, which exhibit a more complex precipitation pattern that is influenced by the strength of westerly jet in addition to the Asian monsoon. The increased westerly jet during the ‘Little Ice Age’ (LIA) caused a humid climate in southern China and dry conditions in northern and western China.

Little Ice Age fluctuations of Glaciar Río Manso in the North Patagonian Andes of Argentina

2010 ◽  
Vol 73 (1) ◽  
pp. 96-106 ◽  
Author(s):  
M.H. Masiokas ◽  
B.H. Luckman ◽  
R. Villalba ◽  
A. Ripalta ◽  
J. Rabassa
Keyword(s):  
Little Ice Age ◽  
Ice Age ◽  
Lateral Moraine ◽  
Early Nineteenth Century ◽  
The Past ◽  
The North ◽  
Specific Factors ◽  
Subfossil Wood ◽  
Moraine Ridge ◽  
Patagonian Andes

Little Ice Age (LIA) fluctuations of Glaciar R"o Manso, north Patagonian Andes, Argentina are studied using information from previous work and dendrogeomorphological analyses of living and subfossil wood. The most extensive LIA expansion occurred between the late 1700s and the 1830"1840s. Except for a massive older frontal moraine system apparently predating ca. 2240 14C yr BP and a small section of a south lateral moraine ridge that is at least 300 yr old, the early nineteenth century advance overrode surficial evidence of any earlier LIA glacier events. Over the past 150 yr the gently sloping, heavily debris-covered lower glacier tongue has thinned significantly, but several short periods of readvance or stasis have been identified and tree-ring dated to the mid-1870s, 1890s, 1900s, 1920s, 1950s, and the mid-1970s. Ice mass loss has increased in recent years due to calving into a rapidly growing proglacial lake. The neighboring debris-free and land-based Glaciar Fr"as has also retreated markedly in recent years but shows substantial differences in the timing of the peak LIA advance (early 1600s). This indicates that site-specific factors can have a significant impact on the resulting glacier records and should thus be considered carefully in the development and assessment of regional glacier chronologies.

Cuban stalagmite suggests relationship between Caribbean precipitation and the Atlantic Multidecadal Oscillation during the past 1.3 ka

The Holocene ◽  
2012 ◽  
Vol 22 (12) ◽  
pp. 1405-1412 ◽  
Author(s):  
Claudia Fensterer ◽  
Denis Scholz ◽  
Dirk Hoffmann ◽  
Christoph Spötl ◽  
Jesús M Pajón ◽  
...  
Keyword(s):  
North Atlantic ◽  
Little Ice Age ◽  
Rainfall Intensity ◽  
Thermohaline Circulation ◽  
Atlantic Multidecadal Oscillation ◽  
Ice Age ◽  
The Past ◽  
The North ◽  
Southward Shift ◽  
The North Atlantic

Here we present the first high-resolution δ18O record of a stalagmite from western Cuba. The record reflects precipitation variability in the northwestern Caribbean during the last 1.3 ka and exhibits a correlation to the Atlantic Multidecadal Oscillation (AMO). This suggests a relationship between Caribbean rainfall intensity and North Atlantic sea-surface temperature (SST) anomalies. A potential mechanism for this relationship may be the strength of the Thermohaline Circulation (THC). For a weaker THC, lower SSTs in the North Atlantic possibly lead to a southward shift of the Intertropical Convergence Zone and drier conditions in Cuba. Thus, this Cuban stalagmite records drier conditions during cold phases in the North Atlantic such as the ‘Little Ice Age’. This study contributes to the understanding of teleconnections between North Atlantic SSTs and northern Caribbean climate variability during the past 1.3 ka.

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