How and when glacial runoff is important: Tracing dynamics of meltwater and rainfall contribution to river runoff from headwaters to lowland in the Caucasus Mountains.

As glacier degradation is intensifying worldwide, understanding how and when glacial runoff is important becomes imperative for economic planning and societal adaptation in response to climate change. This research highlights a probable emergence of new low-flow periods, ranging from one to several weeks, with an anticipated 50-90 % reduction in runoff even in major rivers originating in glacierized mountains by the mid to late 21th century. While the predicted decline in annual and monthly runoff appears moderate for most glaciated regions globally, the emergence of new deglaciation-induced summer low flow periods could create critical "bottle necks" constraining effective water resources management. In this study, a nested catchment approach (7.6-2259 km2) in conjunction with an isotopic tracer method (D, 18O), was employed to quantify the seasonal dynamics of snow and glacial meltwater and rainfall contribution to runoff across various scales of river catchments for the underreported Caucasus Mountains. Although the contribution of meltwater was predictably dominant in the headwaters (75-100 %), it still constituted a substantial 50-60 % of river runoff in the lower reaches most of the time from June to September. While the relative capacity for rainwater storage was found to significantly increase with watershed scale, during weeks devoid of noteworthy rainfall, the runoff in river basins with a mere 7 % glaciation basically entirely consists of what is formed in the glacierized headwaters. The glacial runoff was prevalent in the melt component from late July/early August to mid-September: not less than 30-60 % to the total runoff in the headwaters and 30-40 % in the lower reaches. An approach is proposed to account for the spatial heterogeneity of stable water isotopic content within snow cover and glacier ice. Sources of uncertainties and soundness of assumptions typically used for isotopic hydrograph separation are discussed with particular consideration given to the study objectives.

Tree-ring data set for dendroclimatic reconstructions and dendrochronological dating in European Russia.

The data set presented represents 15 years of collection. It contains tree-ring width measurements from 64 sites of living trees and ten historical chronologies based on archaeological and construction wood up to year 572 CE, altogether 2909 tree-ring series and more than 450000 measured and cross-dated tree rings. It covers the vast territory of European Russia, including its forested northern and central parts, and the Northern Caucasus mountains. The potential use of these data include climatic reconstructions of regional and hemispheric scale, dendrochronological dating of historical and cultural wood, ecological and remote sensing studies.

The Great Acceleration of fragrances and PAHs archived in an ice core from Elbrus, Caucasus.

The Great Acceleration of the anthropogenic impact on the Earth system is marked by the ubiquitous distribution of anthropogenic materials throughout the global environment, including technofossils, radionuclides and the exponential increases of methane and carbon dioxide concentrations. However, personal care products as direct tracers of human domestic habits are often overlooked. Here, we present the first research combining fragrances, as novel personal care products, and polycyclic aromatic hydrocarbons (PAHs) as combustion and industrial markers, across the onset of the Great Acceleration in the Elbrus, Caucasus, ice core. This archive extends from the 1930s to 2005, spanning the profound changes in the relationship between humans and the environment during the twentieth century. Concentrations of both fragrances and PAHs rose throughout the considered period, reflecting the development of the Anthropocene. However, within this rising trend, remarkable decreases of the tracers track the major socioeconomic crises that occurred in Eastern Europe during the second half of the twentieth century.

Disappearance of the last tropical glaciers in the Western Pacific Warm Pool (Papua, Indonesia) appears imminent.

The glaciers near Puncak Jaya in Papua, Indonesia, the highest peak between the Himalayas and the Andes, are the last remaining tropical glaciers in the West Pacific Warm Pool (WPWP). Here, we report the recent, rapid retreat of the glaciers near Puncak Jaya by quantifying the loss of ice coverage and reduction of ice thickness over the last 8 y. Photographs and measurements of a 30-m accumulation stake anchored to bedrock on the summit of one of these glaciers document a rapid pace in the loss of ice cover and a ∼5.4-fold increase in the thinning rate, which was augmented by the strong 2015-2016 El Niño. At the current rate of ice loss, these glaciers will likely disappear within the next decade. To further understand the mechanisms driving the observed retreat of these glaciers, 2 ∼32-m-long ice cores to bedrock recovered in mid-2010 are used to reconstruct the tropical Pacific climate variability over approximately the past half-century on a quasi-interannual timescale. The ice core oxygen isotopic ratios show a significant positive linear trend since 1964 CE (0.018 ± 0.008‰ per year; P < 0.03) and also suggest that the glaciers' retreat is augmented by El Niño-Southern Oscillation processes, such as convection and warming of the atmosphere and sea surface. These Papua glaciers provide the only tropical records of ice core-derived climate variability for the WPWP.

Kilimanjaro ice core records: evidence of holocene climate change in tropical Africa.

Six ice cores from Kilimanjaro provide an approximately 11.7-thousand-year record of Holocene climate and environmental variability for eastern equatorial Africa, including three periods of abrupt climate change: approximately 8.3, approximately 5.2, and approximately 4 thousand years ago (ka). The latter is coincident with the "First Dark Age," the period of the greatest historically recorded drought in tropical Africa. Variable deposition of F- and Na+ during the African Humid Period suggests rapidly fluctuating lake levels between approximately 11.7 and 4 ka. Over the 20th century, the areal extent of Kilimanjaro's ice fields has decreased approximately 80%, and if current climatological conditions persist, the remaining ice fields are likely to disappear between 2015 and 2020.