Tundra vegetation stability versus lake-basin variability on the Yukon Coastal Plain (NW Canada) during the past three centuries

The Holocene ◽  
2017 ◽  
Vol 27 (12) ◽  
pp. 1846-1858 ◽  
Author(s):  
Juliane Wolter ◽  
Hugues Lantuit ◽  
Ulrike Herzschuh ◽  
Samuel Stettner ◽  
Michael Fritz
Keyword(s):  
Coastal Plain ◽  
Ice Age ◽  
Lake Basin ◽  
Climatic Warming ◽  
Vegetation Development ◽  
Ams Radiocarbon Dating ◽  
The Past ◽  
Decadal Scale ◽  
Depth Relationship ◽  
The Impact

Palaeoclimatic reconstructions of the northern Yukon show cooler conditions before AD 1850 followed by gradual warming, and 20th-century temperature measurements indicate decadal-scale temperature fluctuations. The impact of climate on regional vegetation and lake systems has seldom been observed on this scale, however. With this study, we provide a sub-decadal reconstruction of regional vegetation and lake-basin development for the past 300 years, covering the ‘Little Ice Age’ and the period of recent warming, in low Arctic tundra. We analysed a short lake sediment core from the Yukon Coastal Plain. The age–depth relationship of the core is based on 210Pb/137Cs validated by AMS radiocarbon dating. We analysed terrestrial pollen abundances as proxies for regional vegetation development, and we used grain size and biogeochemical analyses (TOC, TN, TOC/TN, δ13C) and the analysis of semiaquatic pollen to describe the lake development. Stable abundances of regional pollen taxa between AD 1730 and AD 2012 accompanied by climatic warming indicated that the regional vegetation was not sensitive to climate change. Based on changes in TOC/TN, δ13C and pollen of shallow-water taxa, we reconstructed an increase in lake water depth after AD 1910 that likely followed climatic warming. We attributed this development to climate-driven thaw subsidence in the lake basin. The impact of widespread permafrost thaw on regional vegetation needs to be better constrained in order to predict the limits of vegetation stability and drivers of lake changes in the region.

Reconstruction of the hydrologic history of a shallow Patagonian steppe lake during the past 700 yr, using chemical, geologic, and biological proxies

2017 ◽  
Vol 87 (2) ◽  
pp. 208-226 ◽  
Author(s):  
Corina Coviaga ◽  
Andrea Rizzo ◽  
Patricia Pérez ◽  
Romina Daga ◽  
Daniel Poiré ◽  
...  
Keyword(s):  
Twentieth Century ◽  
High Salinity ◽  
Southern Annular Mode ◽  
Ice Age ◽  
Late Nineteenth Century ◽  
Lake Basin ◽  
The Past ◽  
High Lake Level ◽  
Moderate Salinity ◽  
History Of

AbstractThe limnological conditions during the past 700 yr were reconstructed based on multiproxy analysis of a short sedimentary sequence from El Toro Lake (~40°S, 70°W). Mineralogical and geochemical features, as well as ostracods and chironomids, record hydrologic changes in the El Toro Lake basin. The ostracod Limnocythere rionegroensis var. 1, a reliable indicator of high salinity, and Eucypris fontana, a euryhaline species with preferences for moderate-salinity waters, are studied as paleolimnological proxies. The chironomid fauna indicates less saline conditions in the mid-twentieth century. These salinity changes are interpreted in terms of negative–positive hydrologic balance. High lake level and low salinity between AD 1500 and 1700 match with the wetter and colder climate during the second pulse of the Little Ice Age in northern Patagonia. High-salinity conditions occurred during the late nineteenth century, corresponding to the driest period during the past 400 yr in northeastern Patagonia. An increase in the precipitation around the middle of the twentieth century, in contrast to the records from the Chilean side of the mountains, correlates with a positive phase of the Southern Annular Mode. This is associated, in turn, with a strengthening, poleward shift of the midlatitude westerlies, possibly enhancing easterly moist air flows into central-north Patagonia.

scholarly journals ТРАНСФОРМАЦИЯ РАСТИТЕЛЬНОСТИ ДОЛИНЫ В СРЕДНЕМ ТЕЧЕНИИ Р. РАЗДОЛЬНАЯ (ПРИМОРСКИЙ КРАЙ) ПО ДАННЫМ СПОРОВО-ПЫЛЬЦЕВОГО АНАЛИЗА

2019 ◽  
Author(s):  
T.V. Kornyushenko
Keyword(s):  
Pinus Densiflora ◽  
Agricultural Landscapes ◽  
Ice Age ◽  
Anthropogenic Factors ◽  
Vegetation Development ◽  
Surrounding Areas ◽  
The Impact ◽  
Natural And Anthropogenic Factors ◽  
Birch Forests

Изучен характер изменений растительности в результате климатических осцилляций в среднем течении р. Раздольная и близлежащих водораздельных пространств, начиная с конца среднего голоцена и при неоднократной трансформации ландшафтов при сельскохозяйственном освоении. Развитие растительности проходило в контрастных климатических условиях, наиболее сильно изменялась увлажненность. Детально реконструкции проведены для последних 2 тыс. кал. л. Изучение споровопыльцевых комплексов позволило выделить шесть споровопыльцевых зон, а также определить специфику формирования палиноспектров, которые включают пыльцу и споры растений, произраставших на данной территории, и пыльцу, принесенную воздушными и водными потоками, в том числе древнюю из нижнемеловых и палеогеннеогеновых отложений. Разрезы включают погребенную почву, сформированную в засушливый период во второй половине позднего голоцена. В это время были широко распространены остепненные полынные, разнотравные луга и березовые редколесья. Климатические условия в конце VIIX вв. постепенно стали более теплыми и влажными. Снижение температуры при высоком увлажнении в малый ледниковый период с постоянным обновлением субстрата на пойме во время наводнений привело к увеличению площадей, занятых сообществами березы овальнолистной. В лесной растительности низкогорья увеличилось участие сосны густоцветковой и берез. Споровопыльцевые комплексы включают пыльцу темнохвойных, в том числе кедра корейского, принесенную во время наводнений из верховий бассейна. Слабо изученным вопросом является оценка воздействия человека на природную среду в средневековье и более ранние эпохи. Не всегда есть информация о том, какой природный облик имела растительность до преобразования в ходе хозяйственной деятельности. Район работ был выбран около Старореченского городища, что дало возможность оценить влияние природопользования во времена Бохайского государства на основе анализа споровопыльцевых комплексов. Проанализирована роль антропогенного фактора в развитии растительности во время заселения долины первопоселенцами XIXначала XX века и при развитии современных агрокомплексов.Studies of floodplain section provided materials for reconstructing a relative importance of natural and anthropogenic factors in the vegetation development in the Razdolnaya (Suifun) River basin near the Starorechenskoye site attributed to the Bohai culture. The transformation of vegetation in the middle reaches of the Razdolnaya River and surrounding areas was influenced by climate change, since the end of the middle Holocene, the impact on vegetation has increased under the influence of agricultural activities. Six pollen zones were distinguished. The studied sequences include a paleosol that developed during a prolonged period of drought at the 2nd half of the late Holocene. The period was noted for a wide occurrence of steppe and forb meadows with wormwood, and open birch forests. The climate became gradually warmer and more humid since the late 7th to 10th centuries. A decrease in temperature at a sufficiently high humidity in the Little Ice Age (the 13th 19th centuries) led to an increase in the areas occupied by the Betula ovalifolia communities. The pollen assemblages display an appearance of dark conifers and Korean pine pollen brought by floods from the upper reaches of the river. In Pinus densiflora and birches gained in importance in the forests of mountain. The recent pollen spectra are indicative of the wide development of agricultural landscapes. The anthropogenic influence to the vegetation was connected with Bohai settlers. The role of the anthropogenic factor in the development of vegetation during the settlement of the valley by the first settlers of the XIXearly XX century and the development of modern agrocomplexes is analyzed.

scholarly journals The Impact of the Little Ice Age on Coccolithophores in the Central Mediterranea Sea

2010 ◽  
Vol 6 (6) ◽  
pp. 795-805 ◽  
Author(s):  
A. Incarbona ◽  
P. Ziveri ◽  
E. Di Stefano ◽  
F. Lirer ◽  
G. Mortyn ◽  
...  
Keyword(s):  
Little Ice Age ◽  
Vertical Mixing ◽  
Ice Age ◽  
Tyrrhenian Sea ◽  
Central Mediterranean ◽  
210Pb Activity ◽  
Decadal Scale ◽  
Lowermost Part ◽  
Sicily Channel ◽  
The Impact

Abstract. The Little Ice Age (LIA) is the last episode of a series of Holocene climatic anomalies. There is still little knowledge on the response of the marine environment to the pronounced cooling of the LIA and to the transition towards the 20th century global warming. Here we present decadal-scale coccolithophore data from four short cores recovered from the central Mediterranean Sea (northern Sicily Channel and Tyrrhenian Sea), which on the basis of 210Pb activity span the last 200–350 years. The lowermost part of the record of one of the cores from the Sicily Channel, Station 407, which extends down to 1650 AD, is characterized by drastic changes in productivity. Specifically, below 1850 AD, the decrease in abundance of F. profunda and the increase of placoliths, suggest increased productivity. The chronology of this change is related to the main phase of the Little Ice Age, which might have impacted the hydrography of the southern coast of Sicily and promoted vertical mixing in the water column. The comparison with climatic forcings points out the importance of stronger and prolonged northerly winds, together with decreased solar irradiance.

scholarly journals Historically unprecedented global glacier decline in the early 21st century

2015 ◽  
Vol 61 (228) ◽  
pp. 745-762 ◽  
Author(s):  
Michael Zemp ◽  
Holger Frey ◽  
Isabelle Gärtner-Roer ◽  
Samuel U. Nussbaumer ◽  
Martin Hoelzle ◽  
...  
Keyword(s):  
21St Century ◽  
Global Scale ◽  
Ice Age ◽  
Early 21St Century ◽  
Sea Level Fluctuations ◽  
Decadal Scale ◽  
The World ◽  
Global Sea Level ◽  
Monitoring Service ◽  
The Impact

AbstractObservations show that glaciers around the world are in retreat and losing mass. Internationally coordinated for over a century, glacier monitoring activities provide an unprecedented dataset of glacier observations from ground, air and space. Glacier studies generally select specific parts of these datasets to obtain optimal assessments of the mass-balance data relating to the impact that glaciers exercise on global sea-level fluctuations or on regional runoff. In this study we provide an overview and analysis of the main observational datasets compiled by the World Glacier Monitoring Service (WGMS). The dataset on glacier front variations (∼42 000 since 1600) delivers clear evidence that centennial glacier retreat is a global phenomenon. Intermittent readvance periods at regional and decadal scale are normally restricted to a subsample of glaciers and have not come close to achieving the maximum positions of the Little Ice Age (or Holocene). Glaciological and geodetic observations (∼5200 since 1850) show that the rates of early 21st-century mass loss are without precedent on a global scale, at least for the time period observed and probably also for recorded history, as indicated also in reconstructions from written and illustrated documents. This strong imbalance implies that glaciers in many regions will very likely suffer further ice loss, even if climate remains stable.

The signal of climate changes over the last two millennia in the Gulf of St. Lawrence, eastern Canada

2021 ◽  
pp. 1-16
Author(s):  
Xiner Wu ◽  
Anne de Vernal ◽  
Bianca Fréchette ◽  
Matthias Moros ◽  
Kerstin Perner
Keyword(s):  
Climate Changes ◽  
Regional Scale ◽  
Ice Age ◽  
Eastern Canada ◽  
Air Masses ◽  
The Past ◽  
Wind Regimes ◽  
Natural Climate ◽  
The Last Two Millennia ◽  
The Impact

Abstract Climate changes over the past two millennia in the central part of the Gulf of St. Lawrence are documented in this paper with the aim of determining and understanding the natural climate variability and the impact of anthropogenic forcing at a regional scale. The palynological content (dinocysts, pollen, and spores) of the composite marine sediment core MSM46-03 collected in the Laurentian Channel was used to reconstruct oceanographic and climatic changes with a multidecadal temporal resolution. Sea-surface conditions, including summer salinity and temperature, sea-ice cover, and primary productivity, were reconstructed from dinocyst assemblages. Results revealed a remarkable cooling trend of about 4°C after 1230 cal yr BP (720 CE) and a culmination with a cold pulse dated to 170–40 cal yr BP (1780–1910 CE), which likely corresponds to the regional signal of the Little Ice Age. This cold interval was followed by a rapid warming of about 3°C. In the pollen assemblages, the decrease of Pinus abundance over the past 1700 yr suggests changes in wind regimes, likely resulting from increased southerly incursions of cold and dry Arctic air masses into southeastern Canada.

scholarly journals Climatic warming, glacier recession and runoff from Alpine basins after the Little Ice Age maximum

2008 ◽  
Vol 48 ◽  
pp. 119-124 ◽  
Author(s):  
David N. Collins
Keyword(s):  
Little Ice Age ◽  
Annual Runoff ◽  
Ice Age ◽  
Climatic Data ◽  
Climatic Warming ◽  
Glacier Surface ◽  
Glacier Recession ◽  
Warming Period ◽  
Summer Temperatures ◽  
The Impact

AbstractRecords of discharge of rivers draining Alpine basins with between 0 and ~70% ice cover, in the upper Aare and Rhône catchments, Switzerland, for the period 1894–2006 have been examined together with climatic data for 1866–2006, with a view to assessing the effects on runoff from glacierized basins of climatic warming coupled with glacier recession following the Little Ice Age maximum. Annual runoff from ice-free basins reflects precipitation variations, rising from minima between 1880 and 1910 to maxima between the late 1960s and early 1980s. The more highly glacierized the basin, the more runoff mimicked mean May–September air temperature during two periods of warming. Runoff increased gradually from the 1900s, rapidly in the 1940s, before decreasing to the late 1970s. Rising runoff levels during the second warming period failed to exceed those attained during the first, despite higher summer temperatures. Although temperatures continued to rise, discharge from glacierized basins declined after reaching maxima in the late 1980s to early 1990s. In the first warming period, rising specific melt rates augmented by increasing precipitation opposed the impact of declining glacier area on runoff. Although melt continued to increase in the second period, enhanced melting (even in the exceptionally warm summer of 2003) appears to have been insufficient to offset reducing glacier surface area exposed to melt, low or reducing levels of precipitation, and increasing evaporation. Thus runoff from glacierized basins peaked in the late 1940s to early 1950s.

scholarly journals Calcareous nannofossil assemblages from the Central Mediterranean Sea over the last four centuries: the impact of the little ice age

2010 ◽  
Vol 6 (3) ◽  
pp. 817-866 ◽  
Author(s):  
A. Incarbona ◽  
P. Ziveri ◽  
E. Di Stefano ◽  
F. Lirer ◽  
G. Mortyn ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Little Ice Age ◽  
Ice Age ◽  
Tyrrhenian Sea ◽  
Calcareous Nannofossil ◽  
Central Mediterranean ◽  
Decadal Scale ◽  
Central Mediterranean Sea ◽  
Sicily Channel ◽  
The Impact

Abstract. We present decadal-scale calcareous nannofossil data from four short cores (Station 272, 37° 17' N, 12° 48' E, 226 m depth; St 342, 36° 42' N, 13° 55' E, 858.2 m depth; St 407, 36° 23' N, 14° 27' E, 345.4 m depth; C90-1M, 40° 36' N, 14° 42' E, 103.4 m depth) recovered in the central Mediterranean Sea (northern Sicily Channel and Tyrrhenian Sea), which, on the basis of 210Pb activity span the last 200–350 years. Assemblages are dominated by placoliths, mostly Emiliania huxleyi, while, at least in the Sicily Channel sediments, Florisphaera profunda was an important part of the coccolithophore community. The paleoenvironmental reconstruction, based on ecological preference of species and groups, suggests that the Tyrrhenian core C90-1M maintained higher productivity levels over recent centuries, with respect to the Sicily Channel sites, possibly because of more pronounced winter phytoplankton blooms, in agreement with modern primary productivity variations over the last ten years. The lowermost part of the record of one of the cores from the Sicily Channel, Station 407, which extends down to 1650 AD, is characterized by drastic changes in productivity. Specifically, below 1850 AD, the decrease in abundance of F. profunda and the increase of placoliths, suggest increased productivity. The chronology of this change is related to the main phase of the Little Ice Age, which might have impacted the hydrography of the southern coast of Sicily and promoted vertical mixing in the water column. The comparison with climatic forcings points out the importance of stronger and prolonged northerlies, together with decreased solar irradiance. The identification of the LIA in the northern Sicily Channel cover the Bond cycle BO that was missing in a previous study of Holocene climatic anomalies in the Sicily Channel. Finally, we suggest that major abundance changes in reworked nannofossil specimens, recorded in the Tyrrhenian core C90-1M, might be linked to variations in terrigenous supply from land. Paradoxically, higher amounts of reworking correspond to dry periods. We argue that soil and rock vulnerability is enhanced during times of prolonged drought and vegetation cover loss.

scholarly journals Effect of changing ocean circulation on deep ocean temperature in the last millennium

2020 ◽  
Vol 11 (4) ◽  
pp. 925-951
Author(s):  
Jeemijn Scheen ◽  
Thomas F. Stocker
Keyword(s):  
Surface Temperature ◽  
Ocean Circulation ◽  
Little Ice Age ◽  
Deep Ocean ◽  
Meridional Overturning Circulation ◽  
Ice Age ◽  
Ocean Temperature ◽  
Temperature Anomalies ◽  
The Past ◽  
The Impact

Abstract. Paleoreconstructions and modern observations provide us with anomalies of surface temperature over the past millennium. The history of deep ocean temperatures is much less well-known and was simulated in a recent study for the past 2000 years under forced surface temperature anomalies and fixed ocean circulation. In this study, we simulate the past 800 years with an illustrative forcing scenario in the Bern3D ocean model, which enables us to assess the impact of changes in ocean circulation on deep ocean temperature. We quantify the effect of changing ocean circulation by comparing transient simulations (where the ocean dynamically adjusts to anomalies in surface temperature – hence density) to simulations with fixed ocean circulation. We decompose temperature, ocean heat content and meridional heat transport into the contributions from changing ocean circulation and changing sea surface temperature (SST). In the deep ocean, the contribution from changing ocean circulation is found to be as important as the changing SST signal itself. Firstly, the small changes in ocean circulation amplify the Little Ice Age signal at around 3 km depth by at least a factor of 2, depending on the basin. Secondly, they fasten the arrival of this atmospheric signal in the Pacific and Southern Ocean at all depths, whereas they delay the arrival in the Atlantic between about 2.5 and 3.5 km by two centuries. This delay is explained by an initial competition between the Little Ice Age cooling and a warming due to an increase in relatively warmer North Atlantic Deep Water at the cost of Antarctic Bottom Water. Under the consecutive Atlantic meridional overturning circulation (AMOC) slowdown, this shift in water masses is inverted and ageing of the water causes a late additional cooling. Our results suggest that small changes in ocean circulation can have a large impact on the amplitude and timing of ocean temperature anomalies below 2 km depth.

Fluorescent potentiometric dyes for membrane-potential imaging

1994 ◽  
Vol 52 ◽  
pp. 166-167
Author(s):  
Leslie M. Loew
Keyword(s):  
Membrane Potential ◽  
Single Cells ◽  
Quantitative Imaging ◽  
Optical Recording ◽  
Biological Processes ◽  
Major Focus ◽  
The Past ◽  
Excitable Systems ◽  
Major Application ◽  
The Impact

A major application of potentiometric dyes has been the multisite optical recording of electrical activity in excitable systems. After being championed by L.B. Cohen and his colleagues for the past 20 years, the impact of this technology is rapidly being felt and is spreading to an increasing number of neuroscience laboratories. A second class of experiments involves using dyes to image membrane potential distributions in single cells by digital imaging microscopy - a major focus of this lab. These studies usually do not require the temporal resolution of multisite optical recording, being primarily focussed on slow cell biological processes, and therefore can achieve much higher spatial resolution. We have developed 2 methods for quantitative imaging of membrane potential. One method uses dual wavelength imaging of membrane-staining dyes and the other uses quantitative 3D imaging of a fluorescent lipophilic cation; the dyes used in each case were synthesized for this purpose in this laboratory.

Perceived Burden of Informal Caregivers of a Chronically Ill Older Family Member

GeroPsych ◽  
2011 ◽  
Vol 24 (3) ◽  
pp. 143-154 ◽  
Author(s):  
Elmar Gräßel ◽  
Raffaela Adabbo
Keyword(s):  
Family Member ◽  
Informal Caregiver ◽  
Chronically Ill ◽  
Stress Model ◽  
The Past ◽  
Perceived Burden ◽  
Hypothetical Construct ◽  
Care Situation ◽  
The Impact ◽  
Further Development

The burden of caregivers has been intensively researched for the past 30 years and has resulted in a multitude of individual findings. This review illustrates the significance of the hypothetical construct of perceived burden for the further development and design of the homecare situation. Following explanations regarding the term informal caregiver, we derive the construct burden from its conceptual association with the transactional stress model of Lazarus and Folkman. Once the extent and characteristics of burden have been set forth, we then present the impact of perceived burden as the care situation. The question of predictors of burden will lead into the last section from which implications can be derived for homecare and relief of caregivers.

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