scholarly journals Holocene glaciation in the Rwenzori Mountains, Uganda

2020 ◽  
Author(s):  
Margaret S. Jackson ◽  
Meredith A. Kelly ◽  
James M. Russell ◽  
Alice M. Doughty ◽  
Jennifer A. Howley ◽  
...  
Keyword(s):  
Late Holocene ◽  
Early Holocene ◽  
Future Climate Change ◽  
Rwenzori Mountains ◽  
Tropical Regions ◽  
Temperature Changes ◽  
Tropical Glaciers ◽  
Low Latitudes ◽  
The Tropics ◽  
Exposure Ages

Abstract. Tropical glaciers are retreating rapidly, threatening alpine ecosystems across the low latitudes. Understanding how tropical glaciers responded to past periods of warming is crucial for predicting and adapting to future climate change, yet relatively little is known about glacial fluctuations in tropical regions during the recent past (i.e., the Holocene Epoch). This is particularly true in the African tropics, where data constraining the timing and magnitude of Holocene glacial fluctuations in the region are sparse and where temperatures during the middle Holocene were perhaps as warm as or warmer than today. Here we present new beryllium-10 surface-exposure ages that constrain Holocene glacial extents in the equatorial Rwenzori Mountains, Uganda. These results document rapid Early Holocene (~11.7–8.2 ka) glacial retreat in two separate catchments and indicate that Late Holocene (~4.2 ka-present) deposits mark the greatest expansion of Rwenzori glaciers during the last ~11 ka. Holocene glacial fluctuations elsewhere in tropical Africa and in tropical South America are broadly similar to those in the Rwenzori, with most tropical glaciers retreating rapidly during the Early Holocene and remaining near or inboard of their Late Holocene positions through much of Holocene time. The similarity of Holocene glacial fluctuations across the tropics implies that low-latitude glaciers responded to a common forcing mechanism, most likely temperature. Although the drivers of Holocene temperature changes in the tropics remains enigmatic, these data help constrain the expression of tropical temperature changes in the low latitudes.

scholarly journals A debris-covered glacier at Kerguelen (49°S, 69°E) over the past 15 000 years

2020 ◽  
pp. 1-13
Author(s):  
Joanna Charton ◽  
Vincent Jomelli ◽  
Irene Schimmelpfennig ◽  
Deborah Verfaillie ◽  
Vincent Favier ◽  
...  
Keyword(s):  
Climate Variability ◽  
Late Holocene ◽  
Ice Cores ◽  
Cosmic Ray ◽  
Late Glacial ◽  
Temperature Changes ◽  
Precipitation Changes ◽  
The Antarctic ◽  
Exposure Ages

Abstract Debris-covered glaciers constitute a large part of the world's cryosphere. However, little is known about their long-term response to multi-millennial climate variability, in particular in the Southern Hemisphere. Here, we provide first insights into the response of a debris-covered glacier to multi-millennial climate variability in the sub-Antarctic Kerguelen Archipelago, which can be compared to that of recently investigated debris-free glaciers. We focus on the Gentil Glacier and present 13 new 36Cl cosmic-ray exposure ages from moraine boulders. The Gentil Glacier experienced at least two glacial advances: the first one during the Late Glacial (19.0–11.6 ka) at ~14.3 ka and the second one during the Late Holocene at ~2.6 ka. Both debris-covered and debris-free glaciers advanced broadly synchronously during the Late Glacial, most probably during the Antarctic Cold Reversal event (14.5–12.9 ka). This suggests that both glacier types at Kerguelen were sensitive to abrupt temperature changes recorded in Antarctic ice cores, associated with increased moisture. However, during the Late Holocene, the advance at ~2.6 ka was not observed in other glaciers and seems to be an original feature of the debris-covered Gentil Glacier, related to either distinct dynamics or to distinct sensitivity to precipitation changes.

scholarly journals Improved estimates of glacier change rates at Nevado Coropuna Ice Cap, Peru

2018 ◽  
Vol 64 (244) ◽  
pp. 175-184 ◽  
Author(s):  
WILLIAM H. KOCHTITZKY ◽  
BENJAMIN R. EDWARDS ◽  
ELLYN M. ENDERLIN ◽  
JERSY MARINO ◽  
NELIDA MARINQUE
Keyword(s):  
Water Resources ◽  
Rate Of Change ◽  
Landsat Images ◽  
Tropical Regions ◽  
Tropical Glaciers ◽  
Ice Cap ◽  
Glacier Recession ◽  
Present Rate ◽  
The Tropics ◽  
Accurate Quantification

ABSTRACTAccurate quantification of rates of glacier mass loss is critical for managing water resources and for assessing hazards at ice-clad volcanoes, especially in arid regions like southern Peru. In these regions, glacier and snow melt are crucial dry season water resources. In order to verify previously reported rates of ice area decline at Nevado Coropuna in Peru, which are anomalously rapid for tropical glaciers, we measured changes in ice cap area using 259 Landsat images acquired from 1980 to 2014. We find that Coropuna Ice Cap is presently the most extensive ice mass in the tropics, with an area of 44.1 km2, and has been shrinking at an average area loss rate of 0.409 km2a−1(~0.71% a−1) since 1980. Our estimated rate of change is considerably lower than previous studies (1.4 km2a−1or ~2.43% a−1), but is consistent with other tropical regions, such as the Cordillera Blanca located ~850 km to the NW (~0.68% a−1). Thus, if glacier recession continues at its present rate, our results suggest that Coropuna Ice Cap will likely continue to contribute to water supply for agricultural and domestic uses until ~2120, which is nearly 100 years longer than previously predicted.

scholarly journals Growth and Physiological Responses of Vegetable Crops to Water Deficit Stress

2020 ◽  
pp. 91-101
Author(s):  
Henil D. Vashi ◽  
Prutha P. Patel ◽  
Kirti Bardhan
Keyword(s):  
Drought Stress ◽  
Future Climate Change ◽  
Water Deficit Stress ◽  
Vegetable Production ◽  
Climate Change Scenarios ◽  
Vegetable Crops ◽  
Tropical Regions ◽  
Stress Effects ◽  
Effects Of Drought ◽  
The Tropics

Future climate change scenarios have become a major threat and limitation for global food production. The rise in greenhouse gases and temperature throughout the globe has caused perturbance in the natural seasonal cycles. This causes a threat to nutritional and calorific food security for the ever-increasing population in the South Asian Countries.  Reduction in the amounts of rainfall in the tropics and subtropics has increased the occurrence of drought leading to more frequent water stress affecting the production of crops, including vegetables, which are  predominantly grown in the tropical and sub-tropical regions. India is the second-largest producer of vegetables in the world and heavy consumer of vegetables. The mini-review focused on drought stress effects on the vegetable production and photosynthesis, transpiration, water uptake and other metabolic and developmental processes. Grafting, breeding, cultural and biotechnological strategies are used to combat drought stress and will be used in the future to ease the harmful effects of drought stress.

scholarly journals Genetic basis and adaptation trajectory of soybean from its temperate origin to tropics

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Lidong Dong ◽  
Chao Fang ◽  
Qun Cheng ◽  
Tong Su ◽  
Kun Kou ◽  
...  
Keyword(s):  
Glycine Max ◽  
Genetic Basis ◽  
Edible Oils ◽  
Yield Traits ◽  
The Novel ◽  
Low Latitude ◽  
Tropical Regions ◽  
Genetic Complexity ◽  
Low Latitudes ◽  
The Tropics

AbstractSoybean (Glycine max) serves as a major source of protein and edible oils worldwide. The genetic and genomic bases of the adaptation of soybean to tropical regions remain largely unclear. Here, we identify the novel locus Time of Flowering 16 (Tof16), which confers delay flowering and improve yield at low latitudes and determines that it harbors the soybean homolog of LATE ELONGATED HYPOCOTYL (LHY). Tof16 and the previously identified J locus genetically additively but independently control yield under short-day conditions. More than 80% accessions in low latitude harbor the mutations of tof16 and j, which suggests that loss of functions of Tof16 and J are the major genetic basis of soybean adaptation into tropics. We suggest that maturity and yield traits can be quantitatively improved by modulating the genetic complexity of various alleles of the LHY homologs, J and E1. Our findings uncover the adaptation trajectory of soybean from its temperate origin to the tropics.

scholarly journals Link between East Asian summer monsoon and sedimentation in river-mouth sandbars since the early Holocene preserved in the Yangtze River subaqueous delta front

2020 ◽  
Vol 95 ◽  
pp. 84-96
Author(s):  
Gang Xu ◽  
Jian Liu ◽  
Marcello Gugliotta ◽  
Yoshiki Saito ◽  
Lilei Chen ◽  
...  
Keyword(s):  
Yangtze River ◽  
Late Holocene ◽  
Asian Summer Monsoon ◽  
Yangtze River Basin ◽  
River Mouth ◽  
Early Holocene ◽  
The Yangtze River ◽  
Delta Front ◽  
The Yangtze River Basin ◽  
Asian Summer

AbstractThis paper presents geochemical and grain-size records since the early Holocene in core ECS0702 with a fine chronology frame obtained from the Yangtze River subaqueous delta front. Since ~9500 cal yr BP, the proxy records of chemical weathering from the Yangtze River basin generally exhibit a Holocene optimum in the early Holocene, a weak East Asian summer monsoon (EASM) period during the middle Holocene, and a relatively strong EASM period in the late Holocene. The ~8.2 and ~4.4 cal ka BP cooling events are recorded in core ECS0702. The flooding events reconstructed by the grain-size parameters since the early Holocene suggest that the floods mainly occurred during strong EASM periods and the Yangtze River mouth sandbar caused by the floods mainly formed in the early and late Holocene. The Yangtze River-mouth sandbars since the early Holocene shifted from north to south, affected by tidal currents and the Coriolis force, and more importantly, controlled by the EASM. Our results are of great significance for enriching both the record of Holocene climate change in the Yangtze River basin and knowledge about the formation and evolution progress of the deltas located in monsoon regions.

scholarly journals Dipole patterns in tropical precipitation were pervasive across landmasses throughout Marine Isotope Stage 5

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Katrina Nilsson-Kerr ◽  
Pallavi Anand ◽  
Philip B. Holden ◽  
Steven C. Clemens ◽  
Melanie J. Leng
Keyword(s):  
Large Scale ◽  
Marine Isotope Stage ◽  
Convergence Zone ◽  
Inter Tropical Convergence Zone ◽  
Tropical Regions ◽  
Tropical Precipitation ◽  
Rainfall Patterns ◽  
Marine Isotope Stage 5 ◽  
Climate Cooling ◽  
The Tropics

AbstractMost of Earth’s rain falls in the tropics, often in highly seasonal monsoon rains, which are thought to be coupled to the inter-hemispheric migrations of the Inter-Tropical Convergence Zone in response to the seasonal cycle of insolation. Yet characterization of tropical rainfall behaviour in the geologic past is poor. Here we combine new and existing hydroclimate records from six large-scale tropical regions with fully independent model-based rainfall reconstructions across the last interval of sustained warmth and ensuing climate cooling between 130 to 70 thousand years ago (Marine Isotope Stage 5). Our data-model approach reveals large-scale heterogeneous rainfall patterns in response to changes in climate. We note pervasive dipole-like tropical precipitation patterns, as well as different loci of precipitation throughout Marine Isotope Stage 5 than recorded in the Holocene. These rainfall patterns cannot be solely attributed to meridional shifts in the Inter-Tropical Convergence Zone.

scholarly journals Twenty-first century regional temperature response in Chile based on empirical-statistical downscaling

2021 ◽  
Author(s):  
Sebastian G. Mutz ◽  
Samuel Scherrer ◽  
Ilze Muceniece ◽  
Todd A. Ehlers
Keyword(s):  
Statistical Models ◽  
Temperature Response ◽  
Local Scale ◽  
First Century ◽  
Local Temperature ◽  
Future Climate Change ◽  
Weather Station ◽  
Temperature Changes ◽  
Scale Temperature ◽  
Twenty First Century

AbstractLocal scale estimates of temperature change in the twenty-first century are necessary for informed decision making in both the public and private sector. In order to generate such estimates for Chile, weather station data of the Dirección Meteorológica de Chile are used to identify large-scale predictors for local-scale temperature changes and construct individual empirical-statistical models for each station. The geographical coverage of weather stations ranges from Arica in the North to Punta Arenas in the South. Each model is trained in a cross-validated stepwise linear multiple regression procedure based on (24) weather station records and predictor time series derived from ERA-Interim reanalysis data. The time period 1979–2000 is used for training, while independent data from 2001 to 2015 serves as a basis for assessing model performance. The resulting transfer functions for each station are then directly coupled to MPI-ESM simulations for future climate change under emission scenarios RCP2.6, RCP4.5 and RCP 8.5 to estimate the local temperature response until 2100 A.D. Our investigation into predictors for local scale temperature changes support established knowledge of the main drivers of Chilean climate, i.e. a strong influence of the El Niño Southern Oscillation in northern Chile and frontal system-governed climate in central and southern Chile. Temperature downscaling yields high prediction skill scores (ca. 0.8), with highest scores for the mid-latitudes. When forced with MPI-ESM simulations, the statistical models predict local temperature deviations from the 1979–2015 mean that range between − 0.5–2 K, 0.5–3 K and 2–7 K for RCP2.6, RCP4.5 and RCP8.5 respectively.

scholarly journals Evaluating the role of contracting and expanding rainforest in initiating cycles of speciation across the Isthmus of Panama

2012 ◽  
Vol 279 (1742) ◽  
pp. 3520-3526 ◽  
Author(s):  
Brian Tilston Smith ◽  
Amei Amei ◽  
John Klicka
Keyword(s):  
Bird Species ◽  
Tropical Regions ◽  
Isthmus Of Panama ◽  
Species Pairs ◽  
The Matrix ◽  
High Species Richness ◽  
The Rich ◽  
The Tropics ◽  
The Impact

Climatic and geological changes across time are presumed to have shaped the rich biodiversity of tropical regions. However, the impact climatic drying and subsequent tropical rainforest contraction had on speciation has been controversial because of inconsistent palaeoecological and genetic data. Despite the strong interest in examining the role of climatic change on speciation in the Neotropics there has been few comparative studies, particularly, those that include non-rainforest taxa. We used bird species that inhabit humid or dry habitats that dispersed across the Panamanian Isthmus to characterize temporal and spatial patterns of speciation across this barrier. Here, we show that these two assemblages of birds exhibit temporally different speciation time patterns that supports multiple cycles of speciation. Evidence for these cycles is further corroborated by the finding that both assemblages consist of ‘young’ and ‘old’ species, despite dry habitat species pairs being geographically more distant than pairs of humid habitat species. The matrix of humid and dry habitats in the tropics not only allows for the maintenance of high species richness, but additionally this study suggests that these environments may have promoted speciation. We conclude that differentially expanding and contracting distributions of dry and humid habitats was probably an important contributor to speciation in the tropics.

Sign in / Sign up

Export Citation Format

Share Document