Similar Holocene glaciation histories in tropical South America and Africa

Geology ◽  
2020 ◽  
Author(s):  
Anthony C. Vickers ◽  
Jeremy D. Shakun ◽  
Brent M. Goehring ◽  
Andrew Gorin, ◽  
Meredith A. Kelly ◽  
...  
Keyword(s):  
South America ◽  
Large Scale ◽  
Past Century ◽  
Tropical Glaciers ◽  
The Past ◽  
Ice Cap ◽  
Ice Retreat ◽  
Quelccaya Ice Cap ◽  
The Tropics

Tropical glaciers have retreated alongside warming temperatures over the past century, yet the way in which these trends fit into a long-term geological context is largely unclear. Here, we present reconstructions of Holocene glacier extents relative to today from the Quelccaya ice cap (Peru) and the Rwenzori Mountains (Uganda) based on measurements of in situ14C and 10Be from recently exposed bedrock. Ice-extent histories are similar at both sites and suggest that ice was generally smaller than today during the first half of the Holocene and larger than today for most, if not all, of the past several millennia. The similar glaciation history in South America and Africa suggests that large-scale warming followed by cooling of the tropics during the late Holocene primarily drove ice extent, rather than regional changes in precipitation. Our results also imply that recent tropical ice retreat is anomalous in a multimillennial context.

scholarly journals Global climatology and trends in convective environments from ERA5 and rawinsonde data

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Mateusz Taszarek ◽  
John T. Allen ◽  
Mattia Marchio ◽  
Harold E. Brooks
Keyword(s):  
Large Scale ◽  
Climate Models ◽  
Global Climate ◽  
Convective Available Potential Energy ◽  
Global Climate Models ◽  
Convective Precipitation ◽  
The Past ◽  
The Tropics ◽  
Rawinsonde Data

AbstractGlobally, thunderstorms are responsible for a significant fraction of rainfall, and in the mid-latitudes often produce extreme weather, including large hail, tornadoes and damaging winds. Despite this importance, how the global frequency of thunderstorms and their accompanying hazards has changed over the past 4 decades remains unclear. Large-scale diagnostics applied to global climate models have suggested that the frequency of thunderstorms and their intensity is likely to increase in the future. Here, we show that according to ERA5 convective available potential energy (CAPE) and convective precipitation (CP) have decreased over the tropics and subtropics with simultaneous increases in 0–6 km wind shear (BS06). Conversely, rawinsonde observations paint a different picture across the mid-latitudes with increasing CAPE and significant decreases to BS06. Differing trends and disagreement between ERA5 and rawinsondes observed over some regions suggest that results should be interpreted with caution, especially for CAPE and CP across tropics where uncertainty is the highest and reliable long-term rawinsonde observations are missing.

Estimating the hazard from extreme hail events across regional to local scales

2021 ◽  
Author(s):  
Katharina Schroeer ◽  
Cornelia Schwierz ◽  
Simona Trefalt ◽  
Alessandro Hering ◽  
Urs Germann
Keyword(s):  
Large Scale ◽  
Past Century ◽  
Worst Case ◽  
The Past ◽  
Weather Radars ◽  
Data Archives ◽  
Damage Claims ◽  
Definition Of ◽  
Convective Weather

<p>Hailstorms and associated hail stone sizes are a tricky atmospheric hazard to assess, because the processes leading to severe convective weather are complex and the spatiotemporal scales of the impacts are often small. The high natural variability of hail requires expensive high-resolution, area-covering measurements to establish robust statics. Weather radars help to achieve this, but despite growing data archives, records usually do not yet extend to climatological time scales (≥30y), and reference ground observations to calibrate hail algorithms are still fragmentary. Consequentially, there remain substantial uncertainties regarding the long-term hazard of hail. Nevertheless, stakeholders require estimates of return periods for preventive regulations or as input to downstream impact models, e.g., in the insurance and engineering sector.</p><p>In the project “Hail climatology Switzerland” MeteoSwiss partnered up with three federal offices, the insurance and engineering sectors to establish a common national reference of the occurrence of hail in Switzerland. The deliverables include developing return period maps of extreme hail events. However, the definition of such extremes varies across sectors. For example, stakeholders from damage prevention require impact probabilities of the largest hailstorm onto an average rooftop, whereas reinsurance stakeholders are interested in nation-wide worst-case events. Here we report on the approaches we took in deriving the frequencies of severe hail considering the different stakeholder demands and the challenges and uncertainties we thereby encountered.</p><p>Using newly reprocessed gridded radar hail data, we assess frequencies of observed hail occurrence in Switzerland over 19 years (2002-2020). We further developed a probabilistic hazard model using stochastic resampling of hailstorms, driven by large-scale environmental boundary conditions. In order to take a storm-object perspective on extremes, we isolate more than 40’000 individual hailstorm footprints. This allows us to consider local storm properties such as the distributions of hail stone sizes by storm area and duration. In addition, we identify region-dependent extreme storm properties, which is specifically relevant in the Alpine region, where high and complex topography creates sharp climatic gradients and results from other regions are often not easily transferable.</p><p>Results show that observed storm tracks vary strongly between years, and hail footprints vary substantially by storm type. Comparing our results obtained from the longest radar-based hail record so far, we find that the spatial patterns of hail agree well with existing hazard maps derived, i.a., from damage claims. However, we also find that frequencies of local extreme hail stone sizes may have been underestimated in the past. This is further corroborated by a regionally aggregated comparative analysis of the radar record to historical records of very large hail in Switzerland over the past century.</p>

scholarly journals Thinning of the Quelccaya Ice Cap over the last thirty years

2016 ◽  
Author(s):  
C. D. Chadwell ◽  
D. R. Hardy ◽  
C. Braun ◽  
H. H. Brecher ◽  
L. G. Thompson
Keyword(s):  
Unit Volume ◽  
Environmental Changes ◽  
Statistical Significance ◽  
Geophysical Methods ◽  
Snow Accumulation ◽  
Dual Frequency ◽  
The Past ◽  
Ice Cap ◽  
Ice Surface ◽  
Quelccaya Ice Cap

Abstract. Direct measurements of the decadal response of Tropical glaciers to environmental changes are difficult to acquire within their accumulation zones. In 2013, we used dual-frequency kinematic GPS to re-measure the surface elevations at 46 sites, from the margin to across the summit of the Quelccaya Ice Cap, first measured in 1983 using terrestrial surveying methods. In 2015, six additional sites on the western margin, first observed in 1978, were remeasured. Over the past 30 years, the ice cap summit has thinned by 4.41 ± 0.23 m (2σ), with a maximum ice loss at one site near the margin of 63.4 ± 0.34 m (2σ) over 37 years. Using geophysical methods that located the sub-glacial bedrock, we estimate the unit-volume of ice in 1983 along a profile from the 1983 margin to the summit and then the change in volume from 1983 to 2013 by differencing the surface elevations. Over the past 30 years, 21.2 ± 0.3 % (2σ) of the ice unit-volume has been lost suggesting an average annual mass balance rate of −0.5 ± 0.1 m w.e. a−1 (2σ). Increasing air temperature at high elevations of the Andes is likely a major driver of the observed changes. Specifically, within the ablation zone, thinning is likely caused by a 1–2 m w.e. a−1 increase in melting and sublimation above steady-state.Within the accumulation zone, analysis of annual, dry-season summit pits suggests that surface lowering may be caused by both a slight decrease in net snow accumulation and an increase in firnification rate, though this interpretation yet lacks statistical significance. The role of ice flux changes since 1983/4 remains unconstrained, awaiting updated measurements of ice surface velocities across the ice cap.

scholarly journals A century of genetic homogenization in Baltic salmon—evidence from archival DNA

2021 ◽  
Vol 288 (1949) ◽  
Author(s):  
Johan Östergren ◽  
Stefan Palm ◽  
John Gilbey ◽  
Göran Spong ◽  
Johan Dannewitz ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Large Scale ◽  
Isolation By Distance ◽  
Anthropogenic Impacts ◽  
Genetic Change ◽  
Past Century ◽  
The Baltic Sea ◽  
The Baltic ◽  
Archival Dna

Intra-species genetic homogenization arising from anthropogenic impacts is a major threat to biodiversity. However, few taxa have sufficient historical material to systematically quantify long-term genetic changes. Using archival DNA collected over approximately 100 years, we assessed spatio-temporal genetic change in Atlantic salmon populations across the Baltic Sea, an area heavily impacted by hydropower exploitation and associated with large-scale mitigation stocking. Analysis was carried out by screening 82 SNPs in 1680 individuals from 13 Swedish rivers. We found an overall decrease in genetic divergence and diminished isolation by distance among populations, strongly indicating genetic homogenization over the past century. We further observed an increase in genetic diversity within populations consistent with increased gene flow. The temporal genetic change was lower in larger wild populations than in smaller wild and hatchery-reared ones, indicating that larger populations have been able to support a high number of native spawners in relation to immigrants. Our results demonstrate that stocking practices of salmon in the Baltic Sea have led to the homogenization of populations over the last century, potentially compromising their ability to adapt to environmental change. Stocking of reared fish is common worldwide, and our study is a cautionary example of the potentially long-term negative effects of such activities.

Could marine animal conservation laws be responsible for the decline or extirpation of macroalgal populations in Bermuda over the past century?

2017 ◽  
Vol 60 (6) ◽  
Author(s):  
Craig W. Schneider ◽  
Christopher T. Flook
Keyword(s):  
Early 20Th Century ◽  
Past Century ◽  
Herbarium Specimens ◽  
Marine Animal ◽  
Population Abundance ◽  
Protected Species ◽  
Animal Conservation ◽  
Macroalgal Species ◽  
The Past ◽  
The Tropics

AbstractUsing over 10,000 archival herbarium specimens from Bermuda, we compared the presence or absence of seaweeds from a century ago with our more than 5000 collections from the last 30 years. Populations of parrotfish, important herbivores of macroalgae in the tropics, have increased since the 1993 amendment to the Bermuda 1978 Fisheries (Protected Species) Order. A fish pot ban for Bermuda was put into effect in 1990 to protect a variety of fish including parrotfish and several species of grouper, important predators of parrotfish that were rarely seen in island waters at the time. Intertidal grazing West Indian top shells were reintroduced in 1982 to Bermuda, and since then, along with the rise in parrotfish populations, inshore populations of many macroalgae have dramatically changed. We suggest that several large and abundant Bermuda macroalgal species recorded in the early 20th century appear to have been extirpated or are greatly diminished in sizes of individuals as well as population abundance, and propose that marine animal protections over the past 35 years are a possible reason for the changes we are presently observing.

scholarly journals Changes in Eurasian glaciation during the past century: glacier mass balance and ice-core evidence

1997 ◽  
Vol 24 ◽  
pp. 283-287 ◽  
Author(s):  
Vladimir N. Mikhalenko
Keyword(s):  
Mass Balance ◽  
Ice Core ◽  
Climatic Conditions ◽  
Tien Shan ◽  
The Arctic ◽  
Past Century ◽  
Glacier Mass Balance ◽  
The Past ◽  
Ice Cap ◽  
Glacier Ice

Glaciers of both the Arctic and mid-latitude mountain systems within Eurasia have retreated intensively during the past century. Measured and reconstructed glacier mass balances show that glacier retreat began around the 1880s. The mean annual mass-balance value for 1880–1990 was −480 mm a−1 for glaciers with maritime climatic conditions, and −140 mm a−1 for continental glaciers. It can be concluded that warming in the Caucasus occurred during at least the last 60 years, according to the distribution of crystal sizes in an ice core from the Dzhantugan firn plateau. Temperatures measured in 1962 at 20 m on the Gregoriev ice cap, Tien Shan, were −4.2°C while in 1990 they were −2°C, a warming of 2.2°C over 28 years. Changes in the isotopic composition of glacier ice during the 20th century indicate recent and continuing warming in different regions of Eurasia. The δ18O records reveal an enrichment at the Gregoriev ice cap during the last 50 years, while surface temperatures at the Tien Shan meteorological station have increased 0.5°C since 1930.

scholarly journals Consistent regional fluxes of CH<sub>4</sub> and CO<sub>2</sub> inferred from GOSAT proxy XCH<sub>4</sub> : XCO<sub>2</sub> retrievals, 2010–2014

2017 ◽  
Vol 17 (7) ◽  
pp. 4781-4797 ◽  
Author(s):  
Liang Feng ◽  
Paul I. Palmer ◽  
Hartmut Bösch ◽  
Robert J. Parker ◽  
Alex J. Webb ◽  
...  
Keyword(s):  
South America ◽  
Large Scale ◽  
A Priori ◽  
Co2 Fluxes ◽  
A Posteriori ◽  
Data Products ◽  
The Tropics ◽  
Regional Fluxes ◽  
Tropical South America

Abstract. We use the GEOS-Chem global 3-D model of atmospheric chemistry and transport and an ensemble Kalman filter to simultaneously infer regional fluxes of methane (CH4) and carbon dioxide (CO2) directly from GOSAT retrievals of XCH4 : XCO2, using sparse ground-based CH4 and CO2 mole fraction data to anchor the ratio. This work builds on the previously reported theory that takes into account that (1) these ratios are less prone to systematic error than either the full-physics data products or the proxy CH4 data products; and (2) the resulting CH4 and CO2 fluxes are self-consistent. We show that a posteriori fluxes inferred from the GOSAT data generally outperform the fluxes inferred only from in situ data, as expected. GOSAT CH4 and CO2 fluxes are consistent with global growth rates for CO2 and CH4 reported by NOAA and have a range of independent data including new profile measurements (0–7 km) over the Amazon Basin that were collected specifically to help validate GOSAT over this geographical region. We find that large-scale multi-year annual a posteriori CO2 fluxes inferred from GOSAT data are similar to those inferred from the in situ surface data but with smaller uncertainties, particularly over the tropics. GOSAT data are consistent with smaller peak-to-peak seasonal amplitudes of CO2 than either the a priori or in situ inversion, particularly over the tropics and the southern extratropics. Over the northern extratropics, GOSAT data show larger uptake than the a priori but less than the in situ inversion, resulting in small net emissions over the year. We also find evidence that the carbon balance of tropical South America was perturbed following the droughts of 2010 and 2012 with net annual fluxes not returning to an approximate annual balance until 2013. In contrast, GOSAT data significantly changed the a priori spatial distribution of CH4 emission with a 40 % increase over tropical South America and tropical Asia and a smaller decrease over Eurasia and temperate South America. We find no evidence from GOSAT that tropical South American CH4 fluxes were dramatically affected by the two large-scale Amazon droughts. However, we find that GOSAT data are consistent with double seasonal peaks in Amazonian fluxes that are reproduced over the 5 years we studied: a small peak from January to April and a larger peak from June to October, which are likely due to superimposed emissions from different geographical regions.

Genetic maps of the proximal half of chromosome arm 2L of Drosophila melanogaster

Genome ◽  
2007 ◽  
Vol 50 (2) ◽  
pp. 137-141 ◽  
Author(s):  
Sylvia Glen Levine ◽  
Suchot Sunday ◽  
Ruth E. Dörig ◽  
Beat Suter ◽  
Paul Lasko
Keyword(s):  
Drosophila Melanogaster ◽  
Large Scale ◽  
Research Community ◽  
Genetic Maps ◽  
Past Century ◽  
The Past ◽  
Proximal Half ◽  
Chromosome Arm ◽  
Physiologic Function ◽  
Complementation Groups

Drosophila mutants have played an important role in elucidating the physiologic function of genes. Large-scale projects have succeeded in producing mutations in a large proportion of Drosophila genes. Many mutant fly lines have also been produced through the efforts of individual laboratories over the past century. In an effort to make some of these mutants more useful to the research community, we systematically mapped a large number of mutations affecting genes in the proximal half of chromosome arm 2L to more precisely defined regions, defined by deficiency intervals, and, when possible, by individual complementation groups. To further analyze regions 36 and 39–40, we produced 11 new deficiencies with gamma irradiation, and we constructed 6 new deficiencies in region 30–33, using the DrosDel system. trans-heterozygous combinations of deficiencies revealed 5 additional functions, essential for viability or fertility.

Trends in the frequency, extent, and severity of spruce budworm outbreaks in eastern Canada

1983 ◽  
Vol 13 (4) ◽  
pp. 539-547 ◽  
Author(s):  
J. R. Blais
Keyword(s):  
20Th Century ◽  
Large Scale ◽  
Spruce Budworm ◽  
Forest Composition ◽  
Eastern Canada ◽  
Clear Cutting ◽  
The Past ◽  
Spruce Stands ◽  
History Of

The history of spruce budworm (Choristoneurafumiferana (Clem.)) outbreaks for the past 200 to 300 years, for nine regions in eastern Canada, indicates that outbreaks have occurred more frequently in the 20th century than previously. Regionally, 21 outbreaks took place in the past 80 years compared with 9 in the preceding 100 years. Earlier infestations were restricted to specific regions, but in the 20th century they have coalesced and increased in size, the outbreaks of 1910, 1940, and 1970 having covered 10, 25, and 55 million ha respectively. Reasons for the increase in frequency, extent, and severity of outbreaks appear mostly attributable to changes caused by man, in the forest ecosystem. Clear-cutting of pulpwood stands, fire protection, and use of pesticides against budworm favor fir–spruce stands, rendering the forest more prone to budworm attack. The manner and degree to which each of these practices has altered forest composition is discussed. In the future, most of these practices are expected to continue and their effects could intensify, especially in regions of recent application. Other practices, including large-scale planting of white spruce, could further increase the susceptibility of forest stands. Forest management, aimed at reducing the occurrence of extensive fir–spruce stands, has been advocated as a long-term solution to the budworm problem. The implementation of this measure at a time when man's actions result in the proliferation of fir presents a most serious challenge to forest managers.

scholarly journals Glacial areas, lake areas, and snow lines from 1975 to 2012: status of the Cordillera Vilcanota, including the Quelccaya Ice Cap, northern central Andes, Peru

2014 ◽  
Vol 8 (2) ◽  
pp. 359-376 ◽  
Author(s):  
M. N. Hanshaw ◽  
B. Bookhagen
Keyword(s):  
Satellite Images ◽  
Climate Changes ◽  
Spectral Unmixing ◽  
Limited Attention ◽  
Lake Area ◽  
Tropical Andes ◽  
The Past ◽  
Ice Cap ◽  
Downstream Communities ◽  
Quelccaya Ice Cap

Abstract. Glaciers in the tropical Andes of southern Peru have received limited attention compared to glaciers in other regions (both near and far), yet remain of vital importance to agriculture, fresh water, and hydropower supplies of downstream communities. Little is known about recent glacial-area changes and how the glaciers in this region respond to climate changes, and, ultimately, how these changes will affect lake and water supplies. To remedy this, we have used 158 multi-spectral satellite images spanning almost 4 decades, from 1975 to 2012, to obtain glacial- and lake-area outlines for the understudied Cordillera Vilcanota region, including the Quelccaya Ice Cap. Additionally, we have estimated the snow-line altitude of the Quelccaya Ice Cap using spectral unmixing methods. We have made the following four key observations: first, since 1988 glacial areas throughout the Cordillera Vilcanota (1988 glacial area: 361 km2) have been declining at a rate of 3.99 ± 1.15 km2 yr−1 (22 year average, 1988–2010, with 95% confidence interval (CI), n = 8 images). Since 1980, the Quelccaya Ice Cap (1980 glacial area: 63.1 km2) has been declining at a rate of 0.57 ± 0.10 km2 yr−1 (30 year average, 1980–2010, with 95% CI, n = 14). Second, decline rates for individual glacierized regions have been accelerating during the past decade (2000–2010) as compared to the preceding decade (1988–1999) with an average increase from 37.5 to 42.3 × 10−3 km2 yr−1 km−2 (13%). Third, glaciers with lower median elevations are declining at higher rates than those with higher median elevations. Specifically, glaciers with median elevations around 5200 m a.s.l. are retreating to higher elevations at a rate of ~1 m yr−1 faster than glaciers with median elevations around 5400 m a.s.l. Fourth, as glacial regions have decreased, 77% of lakes connected to glacial watersheds have either remained stable or shown a roughly synchronous increase in lake area, while 42% of lakes not connected to glacial watersheds have declined in area (58% have remained stable). Our new and detailed data on glacial and lake areas over 37 years provide an important spatiotemporal assessment of climate variability in this area. These data can be integrated into further studies to analyze inter-annual glacial and lake-area changes and assess hydrologic dependence and consequences for downstream populations.

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