scholarly journals NATURAL ENVIRONMENT OF WESTERN TRANSBAIKALIA IN THE LATE GLACIAL AND LATE HOLOCENE

2021 ◽  
Author(s):  
В.Б. Базарова ◽  
М.С. Лящевская
Keyword(s):  
Pollen Analysis ◽  
Natural Environment ◽  
Late Holocene ◽  
Climate Changes ◽  
Regional Climate ◽  
Late Glacial ◽  
Western Transbaikalia ◽  
Last Glacial ◽  
New Material ◽  
The Last Glacial

Представлен новый материал по исследованию отложений Еравнинской котловины. На основе палинологических и радиоуглеродных данных проведена реконструкция природной среды позднеледниковья и позднего голоцена. Выделены холодные и теплые периоды позднеледниковья, а также становление растительности в позднем голоцене. A new material on the study of sediments of the Eravna basin is presented. The results of pollen analysis clearly indicate the climate changes in the last Glacial and late Holocene. The regional climate became milder and more humid around 14.5–12.5 cal. BP, which corresponds to the Allerød interstadial of the European scale.

A Late Holocene Paleoecological Record from Torrey Pines State Reserve, California

2000 ◽  
Vol 53 (3) ◽  
pp. 341-351 ◽  
Author(s):  
Kenneth L. Cole ◽  
Eugene Wahl
Keyword(s):  
Late Holocene ◽  
Climate Changes ◽  
Regional Climate ◽  
Sediment Chemistry ◽  
Fossil Pollen ◽  
Plant Type ◽  
The North ◽  
Low Genetic Diversity ◽  
Core Site ◽  
Pollen And Spores

AbstractPaleoenvironments of the Torrey Pines State Reserve were reconstructed from a 3600-yr core from Los Peñasquitos Lagoon using fossil pollen, spores, charcoal, chemical stratigraphy, particle size, and magnetic susceptibility. Late Holocene sediments were radiocarbon dated, while the historical sediments were dated using sediment chemistry, fossil pollen, and historical records. At 3600 yr B.P., the estuary was a brackish-water lagoon. By 2800 yr B.P., Poaceae (grass) pollen increased to high levels, suggesting that the rising level of the core site led to its colonization by Spartina foliosa (cord-grass), the lowest-elevation plant type within regional estuaries. An increase in pollen and spores of moisture-dependent species suggests a climate with more available moisture after 2600 yr B.P. This change is similar to that found 280 km to the north at 3250 yr B.P., implying that regional climate changes were time-transgressive from north to south. Increased postsettlement sediment input resulted from nineteenth-century land disturbances caused by grazing and fire. Sedimentation rates increased further in the twentieth century due to closure of the estuarine mouth. The endemic Pinus torreyana (Torrey pine) was present at the site throughout this 3600-yr interval but was less numerous prior to 2100 yr B.P. This history may have contributed to the low genetic diversity of this species.

Charcoal signatures defined by multivariate analysis of charcoal records from 10 lakes in northwest Wisconsin (USA)

2011 ◽  
Vol 75 (1) ◽  
pp. 125-137 ◽  
Author(s):  
Elizabeth A. Lynch ◽  
Sara C. Hotchkiss ◽  
Randy Calcote
Keyword(s):  
Late Holocene ◽  
Climate Changes ◽  
Regional Climate ◽  
Fire Regimes ◽  
Small Scale ◽  
Regional Patterns ◽  
Crown Fires ◽  
Sand Plain ◽  
In Fire ◽  
Standard Techniques

AbstractWe show how sedimentary charcoal records from multiple sites within a single landscape can be used to compare fire histories and reveal small scale patterns in fire regimes. Our objective is to develop strategies for classifying and comparing late-Holocene charcoal records in Midwestern oak- and pine-dominated sand plain ecosystems where fire regimes include a mix of surface and crown fires. Using standard techniques for the analysis of charcoal from lake sediments, we compiled 1000- to 4000-yr-long records of charcoal accumulation and charcoal peak frequencies from 10 small lakes across a sand plain in northwestern Wisconsin. We used cluster analysis to identify six types of charcoal signatures that differ in their charcoal influx rates, amount of grass charcoal, and frequency and magnitude of charcoal peaks. The charcoal records demonstrate that while fire histories vary among sites, there are regional patterns in the occurrence of charcoal signature types that are consistent with expected differences in fire regimes based on regional climate and vegetation reconstructions. The fire histories also show periods of regional change in charcoal signatures occurring during times of regional climate changes at ~700, 1000, and 3500 cal yr BP.

Relationship between peat bed formation and climate changes during the last glacial in the Venice area

2011 ◽  
Vol 238 (1-2) ◽  
pp. 172-180 ◽  
Author(s):  
Massimo Zecchin ◽  
Mauro Caffau ◽  
Luigi Tosi
Keyword(s):  
Climate Changes ◽  
Last Glacial ◽  
The Last Glacial

scholarly journals Climate variability in the Spanish Pyrenees during the last 30,000 yr revealed by the El Portalet sequence

2006 ◽  
Vol 66 (1) ◽  
pp. 38-52 ◽  
Author(s):  
P. González-Sampériz ◽  
B.L. Valero-Garcés ◽  
A. Moreno ◽  
G. Jalut ◽  
J.M. García-Ruiz ◽  
...  
Keyword(s):  
High Resolution ◽  
Climate Variability ◽  
Climate Changes ◽  
Vegetation History ◽  
Ice Cores ◽  
Late Glacial ◽  
Last Glacial ◽  
The North ◽  
Isotopic Analyses ◽  
Spanish Pyrenees

AbstractPalynological, sedimentological and stable isotopic analyses of carbonates and organic matter performed on the El Portalet sequence (1802 m a.s.l., 42°48′00ʺN, 0°23′52ʺW) reflect the paleoclimatic evolution and vegetation history in the central-western Spanish Pyrenees over the last 30,000 yr, and provide a high-resolution record for the late glacial period. Our results confirm previous observations that deglaciation occurred earlier in the Pyrenees than in northern European and Alpine sites and point to a glacial readvance from 22,500 to 18,000 cal yr BP, coinciding with the global last glacial maximum. The patterns shown by the new, high-resolution pollen data from this continental sequence, chronologically constrained by 13 AMS 14C dates, seem to correlate with the rapid climate changes recorded in Greenland ice cores during the last glacial–interglacial transition. Abrupt events observed in northern latitudes (Heinrich events 3 to 1, Oldest and Older Dryas stades, Intra-Allerød Cold Period, and 8200 cal yr BP event) were also identified for the first time in a lacustrine sequence from the central-western Pyrenees as cold and arid periods. The coherent response of the vegetation and the lake system to abrupt climate changes implies an efficient translation of climate variability from the North Atlantic to mid latitudes.

scholarly journals Oceanic forcing of the Eurasian Ice Sheet on millennial time scales during the Last Glacial Period

2018 ◽  
Author(s):  
Jorge Alvarez-Solas ◽  
Rubén Banderas ◽  
Alexander Robinson ◽  
Marisa Montoya
Keyword(s):  
Time Scales ◽  
North Atlantic ◽  
Climate Changes ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Glacial Period ◽  
Last Glacial Period ◽  
Last Glacial ◽  
The Last Glacial ◽  
Millennial Scale

Abstract. The last glacial period (LGP; ca.110–10 ka BP) was marked by the existence of two types of abrupt climatic changes, Dansgaard-Oeschger (DO) and Heinrich (H) events. Although the mechanisms behind these are not fully understood, it is generally accepted that the presence of ice sheets played an important role in their occurrence. While an important effort has been made to investigate the dynamics and evolution of the Laurentide Ice Sheet (LIS) during this period, the Eurasian Ice Sheet (EIS) has not received much attention, in particular from a modeling perspective. However, meltwater discharge from this and other ice sheets surrounding the Nordic Seas is often implied as a potential cause of ocean instabilities that lead to glacial abrupt climate changes. Thus, a better understanding of its variations during the LGP is important to understand its role in glacial abrupt climate changes. Here we investigate the response of the EIS to millennial-scale climate variability during the LGP. We use a hybrid, three-dimensional, thermomechanical ice-sheet model that includes ice shelves and ice streams. The model is forced offline through a novel perturbative approach that includes the effect of both atmospheric and oceanic variations and provides a more realistic treatment of millennial-scale climatic variability than conventional methods. Our results show that the EIS responds with enhanced ice discharge in phase with interstadial warming in the North Atlantic when forced with surface ocean temperatures. Conversely, when subsurface ocean temperatures are used, enhanced ice discharge occurs both during stadials and at the beginning of the interstadials. Separating the atmospheric and oceanic effects demonstrates the major role of the ocean in controlling the dynamics of the EIS on millennial time scales. While the atmospheric forcing alone is only able to produce modest iceberg discharges, warming of the ocean leads to higher rates of iceberg discharges as a result of relatively strong basal melting at the margins of the ice sheet. Together with previous work, our results provide a consistent explanation for the response of the LIS and the EIS to glacial abrupt climate changes, and highlight the need for stronger constraints on the local North Atlantic behavior in order to improve our understanding of the ice sheet's glacial dynamics.

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