Stalagmite geochemical proxy-inferred precipitation records over the past 800 years in northern Italy

2020 ◽  
Author(s):  
C.-C. (River) Shen ◽  
Hsun-Ming Hu ◽  
Véronique Michel ◽  
Patricia Valensi ◽  
Horng-Sheng Mii ◽  
...  
Keyword(s):  
Northern Italy ◽  
Ice Age ◽  
Dry Period ◽  
Calcite Precipitation ◽  
The Past ◽  
Proxy Records ◽  
Increasing Trend ◽  
Dry Conditions ◽  
Precipitation Records ◽  
High Degree

<p>We here present new <sup>230</sup>Th-dated stalagmite multi-proxy records from Toirano cave (44˚ N, 8˚E), northern Italy, characterized by a semi-arid Mediterranean climate with humid winters and dry summers. Eleven U-Th ages was used to build the regional hydroclimate evolution over the past 800 years. Sr/Ca and Ba/Ca records show a similar pattern with an increasing trend at the end of Medieval Warm Period (MWP; 950-1250 C.E.) and a decreasing trend at the inception of Little Ice Age (LIA; 1300 to 1800 C.E). The temperature effect on the Sr partition coefficient in calcite is negligible and no significant influence of deposition rate on Sr/Ca and Ba/Ca is observed. The high degree of co-variation between the two records (r = 0.91; n = 212) suggest the variation should be mainly governed by prior calcite precipitation (PCP). Dry conditions lead to a longer water residence time in the epikarst, enhanced CO<sub>2</sub> degassing and decreasing drip rate, resulting in high Sr/Ca and Ba/Ca ratios due to the preferential removal of Ca during PCP. Our results suggest a dry period during the transition of MCA and LIA in our region.</p>

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 Ocean dynamics, not dust, have controlled equatorial Pacific productivity over the past 500,000 years

2016 ◽  
Vol 113 (22) ◽  
pp. 6119-6124 ◽  
Author(s):  
Gisela Winckler ◽  
Robert F. Anderson ◽  
Samuel L. Jaccard ◽  
Franco Marcantonio
Keyword(s):  
Equatorial Pacific ◽  
Ocean Dynamics ◽  
Ice Age ◽  
Equatorial Pacific Ocean ◽  
Biological Productivity ◽  
Trade Winds ◽  
Equatorial Undercurrent ◽  
Dissolved Iron ◽  
The Past ◽  
Proxy Records

Biological productivity in the equatorial Pacific is relatively high compared with other low-latitude regimes, especially east of the dateline, where divergence driven by the trade winds brings nutrient-rich waters of the Equatorial Undercurrent to the surface. The equatorial Pacific is one of the three principal high-nutrient low-chlorophyll ocean regimes where biological utilization of nitrate and phosphate is limited, in part, by the availability of iron. Throughout most of the equatorial Pacific, upwelling of water from the Equatorial Undercurrent supplies far more dissolved iron than is delivered by dust, by as much as two orders of magnitude. Nevertheless, recent studies have inferred that the greater supply of dust during ice ages stimulated greater utilization of nutrients within the region of upwelling on the equator, thereby contributing to the sequestration of carbon in the ocean interior. Here we present proxy records for dust and for biological productivity over the past 500 ky at three sites spanning the breadth of the equatorial Pacific Ocean to test the dust fertilization hypothesis. Dust supply peaked under glacial conditions, consistent with previous studies, whereas proxies of export production exhibit maxima during ice age terminations. Temporal decoupling between dust supply and biological productivity indicates that other factors, likely involving ocean dynamics, played a greater role than dust in regulating equatorial Pacific productivity.

scholarly journals Variations in surface area of six ice aprons in the Mont-Blanc massif since the Little Ice Age

2020 ◽  
Vol 66 (259) ◽  
pp. 777-789
Author(s):  
Grégoire Guillet ◽  
Ludovic Ravanel
Keyword(s):  
Surface Area ◽  
Little Ice Age ◽  
Ice Age ◽  
High Mountain ◽  
Seasonal Temperature ◽  
Degree Days ◽  
Temperature Variations ◽  
The Past ◽  
Precipitation Records ◽  
Mont Blanc Massif

AbstractDeglaciation of high mountain rockwalls alters slope stability as rockwalls become more sensitive to modifications in environmental factors (e.g. seasonal temperature variations). In the past decades, increasing efforts focused on studying deglaciated Alpine rockwalls. Yet, currently deglaciating rockfaces remain unstudied. Here, we quantify surface area variations of massive ice bodies lying on high mountain rockwalls (ice aprons) in the French sector of the Mont Blanc massif between the end of the Little Ice Age (LIA) and 2018. Surface area estimates are computed from terrestrial and aerial oblique photographs via photogrammetry. This technique allows using photographs taken without scientific intent, and to tap into diverse historical or recent photographic catalogs. We derive an ice apron surface area model from precipitation records and the positive degree-days. The studied ice aprons shrank from 1854 to the 1950s, before expanding until the end of the 1990s. The beginning of the 21st century shows a decrease in surface area, leading to the complete melt of one of the studied ice aprons in 2017. Observed variations correlate with modeled surface area, suggesting strong sensitivity of ice aprons to changes in climatic variables. By studying site-specific correlations, we explore the importance of local drivers over the balance of ice aprons.

scholarly journals Was the Little Ice Age more or less El Niño-like than the Medieval Climate Anomaly? Evidence from hydrological and temperature proxy data

2017 ◽  
Vol 13 (3) ◽  
pp. 267-301 ◽  
Author(s):  
Lilo M. K. Henke ◽  
F. Hugo Lambert ◽  
Dan J. Charman
Keyword(s):  
Little Ice Age ◽  
Large Scale ◽  
Global Climate ◽  
Ice Age ◽  
Medieval Climate Anomaly ◽  
Climate Anomaly ◽  
Proxy Data ◽  
The Past ◽  
Proxy Records

Abstract. The El Niño–Southern Oscillation (ENSO) is the most important source of global climate variability on interannual timescales and has substantial environmental and socio-economic consequences. However, it is unclear how it interacts with large-scale climate states over longer (decadal to centennial) timescales. The instrumental ENSO record is too short for analysing long-term trends and variability and climate models are unable to accurately simulate past ENSO states. Proxy data are used to extend the record, but different proxy sources have produced dissimilar reconstructions of long-term ENSO-like climate change, with some evidence for a temperature–precipitation divergence in ENSO-like climate over the past millennium, in particular during the Medieval Climate Anomaly (MCA; AD  ∼  800–1300) and the Little Ice Age (LIA; AD  ∼  1400–1850). This throws into question the stability of the modern ENSO system and its links to the global climate, which has implications for future projections. Here we use a new statistical approach using weighting based on empirical orthogonal function (EOF) to create two new large-scale reconstructions of ENSO-like climate change derived independently from precipitation proxies and temperature proxies. The method is developed and validated using model-derived pseudo-proxy experiments that address the effects of proxy dating error, resolution, and noise to improve uncertainty estimations. We find no evidence that temperature and precipitation disagree over the ENSO-like state over the past millennium, but neither do they agree strongly. There is no statistically significant difference between the MCA and the LIA in either reconstruction. However, the temperature reconstruction suffers from a lack of high-quality proxy records located in ENSO-sensitive regions, which limits its ability to capture the large-scale ENSO signal. Further expansion of the palaeo-database and improvements to instrumental, satellite, and model representations of ENSO are needed to fully resolve the discrepancies found among proxy records and establish the long-term stability of this important mode of climatic variability.

scholarly journals Climatic history of the northeastern United States during the past 3000 years

2017 ◽  
Vol 13 (10) ◽  
pp. 1355-1379 ◽  
Author(s):  
Jennifer R. Marlon ◽  
Neil Pederson ◽  
Connor Nolan ◽  
Simon Goring ◽  
Bryan Shuman ◽  
...  
Keyword(s):  
Ecosystem Dynamics ◽  
Ice Age ◽  
Extreme Weather Events ◽  
Past Century ◽  
Vegetation Growth ◽  
The Past ◽  
Weather Events ◽  
Dry Conditions ◽  
History Of ◽  
Paleoclimate Records

Abstract. Many ecosystem processes that influence Earth system feedbacks – vegetation growth, water and nutrient cycling, disturbance regimes – are strongly influenced by multidecadal- to millennial-scale climate variations that cannot be directly observed. Paleoclimate records provide information about these variations, forming the basis of our understanding and modeling of them. Fossil pollen records are abundant in the NE US, but cannot simultaneously provide information about paleoclimate and past vegetation in a modeling context because this leads to circular logic. If pollen data are used to constrain past vegetation changes, then the remaining paleoclimate archives in the northeastern US (NE US) are quite limited. Nonetheless, a growing number of diverse reconstructions have been developed but have not yet been examined together. Here we conduct a systematic review, assessment, and comparison of paleotemperature and paleohydrological proxies from the NE US for the last 3000 years. Regional temperature reconstructions (primarily summer) show a long-term cooling trend (1000 BCE–1700 CE) consistent with hemispheric-scale reconstructions, while hydroclimate data show gradually wetter conditions through the present day. Multiple proxies suggest that a prolonged, widespread drought occurred between 550 and 750 CE. Dry conditions are also evident during the Medieval Climate Anomaly, which was warmer and drier than the Little Ice Age and drier than today. There is some evidence for an acceleration of the longer-term wetting trend in the NE US during the past century; coupled with an abrupt shift from decreasing to increasing temperatures in the past century, these changes could have wide-ranging implications for species distributions, ecosystem dynamics, and extreme weather events. More work is needed to gather paleoclimate data in the NE US to make inter-proxy comparisons and to improve estimates of uncertainty in reconstructions.

scholarly journals Variability of summer humidity during the past 800 years on the eastern Tibetan Plateau inferred from δ<sup>18</sup>O of tree-ring cellulose

2015 ◽  
Vol 11 (2) ◽  
pp. 327-337 ◽  
Author(s):  
J. Wernicke ◽  
J. Grießinger ◽  
P. Hochreuther ◽  
A. Bräuning
Keyword(s):  
Relative Humidity ◽  
Tibetan Plateau ◽  
Tree Ring ◽  
Summer Season ◽  
Ice Age ◽  
Transfer Model ◽  
The Tibetan Plateau ◽  
The Past ◽  
Dry Conditions ◽  
Hydroclimatic Variables

Abstract. We present an 800-year δ18O chronology from the eastern part of the Tibetan Plateau (TP). The chronology dates back to AD 1193 and was sampled in AD 1996 from living Juniperus tibetica trees. This first long-term tree-ring-based δ18O chronology for eastern Tibet provides a reliable archive for hydroclimatic reconstructions. Highly significant correlations were obtained with hydroclimatic variables (relative humidity, vapour pressure, and precipitation) during the summer season. We applied a linear transfer model to reconstruct summer season relative humidity variations over the past 800 years. More moist conditions prevailed during the termination of the Medieval Warm Period while a systematic shift during the Little Ice Age is not detectable. A distinct trend towards more dry conditions since the 1870s is apparent. The moisture decline weakened around the 1950s but still shows a negative trend. The mid-19th century humidity decrease is in good accordance with several multiproxy hydroclimate reconstructions for south Tibet. However, the pronounced summer relative humidity decline is stronger on the central and eastern TP. Furthermore, the relative humidity at our study site is significantly linked to the relative humidity at large parts of the TP. Therefore, we deduce that the reconstructed relative humidity is mostly controlled by local and mesoscale climatic drivers, although significant connections to the higher troposphere of west-central Asia were observed.

A high-resolution paleolimnological study of climate and human impacts on Lac Noir, Québec, over the past 1000 yr

2018 ◽  
Vol 91 (2) ◽  
pp. 665-678 ◽  
Author(s):  
Karen Neil ◽  
Konrad Gajewski
Keyword(s):  
Human Impacts ◽  
Ecosystem Dynamics ◽  
Ice Age ◽  
Forest Composition ◽  
Lake Ecosystem ◽  
Nutrient Inputs ◽  
Lake Productivity ◽  
The Past ◽  
Dry Conditions ◽  
Additive Modeling

AbstractDiatom assemblages in lake sediments of Lac Noir, southwestern Québec, were studied at a resolution of 10 yr to determine principal drivers of primary producers for the past ~1000 yr. Generalized additive modeling revealed strong links between broadscale climate intervals of the late Holocene, forest composition, and diatom flora. During the Medieval Warm Period (~AD 1200) and onset of the Little Ice Age (~AD 1450), increases in Tabellaria flocculosa str. IIIp at the expense of Discostella stelligera reflected low lake productivity. At AD 1630, an abrupt shift to cooler temperatures and dry conditions triggered a decline in hemlock (Tsuga), replaced by disturbance and cool-adapted taxa. Greater nutrient availability and soil erosion in the catchment led to a corresponding and rapid increase in diatoms with higher optima for nitrogen, such as Asterionella formosa and Fragilaria crotonensis. After AD 1870, an increase in pollen of taxa associated with disturbances signaled the arrival of Euro-Canadians, and associated nutrient inputs to the lake triggered increases in Stephanodiscus minutulus and Achnanthidium minutissimum. Overall results of the study indicate that climate played an important underlying role in lake-ecosystem dynamics; however, disturbances affecting forest composition had more direct influences on the diatom communities of Lac Noir.

Sensitivity of wetland hydrology to external climate forcing in central Florida

2015 ◽  
Vol 84 (3) ◽  
pp. 287-300 ◽  
Author(s):  
Emmy I. Lammertsma ◽  
Timme H. Donders ◽  
Christof Pearce ◽  
Holger Cremer ◽  
Evelyn E. Gaiser ◽  
...  
Keyword(s):  
Little Ice Age ◽  
Late Holocene ◽  
Wetland Hydrology ◽  
Ice Age ◽  
Climate Forcing ◽  
Central Florida ◽  
The Past ◽  
Proxy Records ◽  
Hydrological Changes ◽  
Multiple Cores

Available proxy records from the Florida peninsula give a varying view on hydrological changes during the late Holocene. Here we evaluate the consistency and sensitivity of local wetland records in relation to hydrological changes over the past ~ 5 ka based on pollen and diatom proxies from peat cores in Highlands Hammock State Park, central Florida. Around 5 cal ka BP, a dynamic floodplain environment is present. Subsequently, a wetland forest establishes, followed by a change to persistent wet conditions between ~ 2.5 and 2.0 ka. Long hydroperiods remain despite gradual succession and basin infilling with maximum wet conditions between ~ 1.3 and 1.0 ka. The wet phase and subsequent strong drying over the last millennium, as indicated by shifts in both pollen and diatom assemblages, can be linked to the early Medieval Warm Period and Little Ice Age, respectively, driven by regionally higher sea-surface temperatures and a temporary northward migration of the Intertropical Convergence Zone. Changes during the 20th century are the result of constructions intended to protect the Highlands Hammock State Park from wildfires. The multiple cores and proxies allow distinguishing local and regional hydrological changes. The peat records reflect relatively subtle climatic changes that are not evident from regional pollen records from lakes.

scholarly journals Secular trends of population attributable risk of overweight and obesity for hypertension among Chinese adults from 1991 to 2011

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jian Gou ◽  
Huiying Wu
Keyword(s):  
Population Attributable Risk ◽  
Attributable Risk ◽  
Secular Trends ◽  
Overweight And Obesity ◽  
Regression Coefficients ◽  
Chinese Adults ◽  
Intervention Effect ◽  
Obesity Epidemic ◽  
The Past ◽  
Increasing Trend

AbstractWe determined if the increasing trend in hypertension can be partly attributed to increasing prevalence of overweight/obesity in China over the past two decades. Data were collected from 1991 to 2011 and the population attributable risk (PAR), which is used to estimate the intervention effect on hypertension if overweight/obese, were eliminated. Linear regression was used to evaluate the secular trends. The age-standardized prevalence of overweight and obesity increased by 26.32% with an overall slope of 1.27% (95% CI: 1.12–1.43%) per year. Hypertension also increased by 12.37% with an overall slope of 0.65% (95% CI: 0.51–0.79%) per year. The adjusted ORs of overweight/obesity for hypertension across the survey years remained unchanged; however, the trend in PAR increased steadily from 27.1 to 44.6% with an overall slope of 0.81% (95% CI: 0.34–1.28%) per year (P = 0.006). There was no significant gender difference in the slopes of increasing PAR, as measured by regression coefficients (β = 0.95% vs. β = 0.63% per year, P = 0.36). Over the past two decades, the increase in the prevalence of hypertension in China was partly attributed to the overweight/obesity epidemic, which highlights the importance of controlling weight and further reducing the burden of hypertension.

scholarly journals Role of Camel Husbandry in Food Security of the Republic of Kazakhstan

Agriculture ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 614
Author(s):  
Ayan Orazov ◽  
Liudmila Nadtochii ◽  
Kazybay Bozymov ◽  
Mariam Muradova ◽  
Araigul Zhumayeva
Keyword(s):  
Food Security ◽  
Meat Products ◽  
Daily Consumption ◽  
Low Level ◽  
The Past ◽  
Self Sufficiency ◽  
The Republic ◽  
Food Security Indicators ◽  
Security Indicators ◽  
High Degree

This paper examines the problem of food security in the Republic of Kazakhstan over the past 10 years. Based on statistical data, an assessment was made of the prevalence of malnutrition among the population of the country, including children under 5 years of age. There has been a trend towards for an improvement in the nutrition of the population for a few indicators; however, further optimization of food security indicators is required to achieve the goals of sustainable development (SDGs) of the FAO WHO Agenda for the period up to 2050 in Kazakhstan and in its individual regions. The paper reflects data on demographic changes over the past 10 years and its self-sufficiency in basic foods for 2019. A high degree of self-sufficiency in meat products (117.6%) is revealed in the population of the Republic of Kazakhstan. However, self-sufficiency in dairy products is at an extremely low level (0.1%). Camel breeding has been successfully developing in the country over the past 10 years. However, the number of camels in the country is still at a low level. Camel milk can be considered as a great source of macronutrients, its daily consumption partially facilitates the problem of Food Security in Kazakhstan.

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