Long-term erosion of the Nepal Himalayas by bedrock landsliding: the role of monsoons, earthquakes and giant landslides Earth Surface Dynamics DOI 10.5194/esurf-7-107-2019 25 January 2019 We mapped eight monsoon-related (> 100 m2) and large (> 0.1 km2) landslides in the Nepal Himalayas since 1970. Adding inventories of Holocene landslides, giant landslides (> 1 km3), and landslides from the 2015 Gorkha earthquake, we constrain the size–frequency distribution of monsoon- and earthquake-induced landslides. Both contribute ~50 % to a long-term (> 10 kyr) total erosion of ~2 mm yr-1, matching the long-term exhumation rate. Large landslides rarer than10Be sampling time drive erosion. Read more
Stable carbon and nitrogen isotopic composition of leaves, litter, and soils of various ecosystems along an elevational and land-use gradient at Mount Kilimanjaro, Tanzania Biogeosciences DOI 10.5194/bg-16-409-2019 25 January 2019 Mount Kilimanjaro is an iconic environmental asset under serious threat due to increasing human pressures and climate change constraints. We studied variations in the stable isotopic composition of carbon and nitrogen in plant, litter, and soil material sampled along a strong land-use and altitudinal gradient. Our results show that, besides management, increasing temperatures in a changing climate may promote carbon and nitrogen losses, thus altering the stability of Kilimanjaro ecosystems. Read more
Positive matrix factorization of organic aerosol: insights from a chemical transport model Atmospheric Chemistry and Physics DOI 10.5194/acp-19-973-2019 24 January 2019 The ability of positive matrix factorization (PMF) factor analysis to identify and quantify the organic aerosol (OA) sources accurately is tested in this modeling study. The estimated uncertainty of the contribution of fresh biomass burning is less than 30 % and of the other primary sources is less than 40 %, when these sources contribute more than 20 % to the OA. Τhe first oxygenated OA factor includes mainly highly aged OA, while the second oxygenated OA factor contains fresher secondary OA. Read more
Heinrich events show two-stage climate response in transient glacial simulations Climate of the Past DOI 10.5194/cp-15-153-2019 24 January 2019 Heinrich events are among the dominant modes of glacial climate variability. They are caused by massive ice discharges from the Laurentide Ice Sheet into the North Atlantic. In previous studies, the climate changes were either seen as resulting from freshwater released from the melt of the discharged icebergs or by ice sheet elevation changes. With a coupled ice sheet–climate model, we show that both effects are relevant with the freshwater effects preceding the ice sheet elevation effects. Read more
Quantifying new water fractions and transit time distributions using ensemble hydrograph separation: theory and benchmark tests Hydrology and Earth System Sciences DOI 10.5194/hess-23-303-2019 18 January 2019 How long does it take for raindrops to become streamflow? Here I propose a new approach to this old problem. I show how we can use time series of isotope data to measure the average fraction of same-day rainfall appearing in streamflow, even if this fraction varies greatly from rainstorm to rainstorm. I show that we can quantify how this fraction changes from small rainstorms to big ones, and from high flows to low flows, and how it changes with the lag time between rainfall and streamflow. Read more
Global atmospheric CO2 inverse models converging on neutral tropical land exchange, but disagreeing on fossil fuel and atmospheric growth rate Biogeosciences DOI 10.5194/bg-16-117-2019 16 January 2019 We have compared global carbon budgets calculated from numerical inverse models and CO2 observations, and evaluated how these systems reproduce vertical gradients in atmospheric CO2 from aircraft measurements. We found that available models have converged on near-neutral tropical total fluxes for several decades, implying consistent sinks in intact tropical forests, and that assumed fossil fuel emissions and predicted atmospheric growth rates are now the dominant axes of disagreement. Read more
A multi-technology analysis of the 2017 North Korean nuclear test Solid Earth DOI 10.5194/se-10-59-2019 15 January 2019 On 3 September 2017 official channels of the Democratic People’s Republic of Korea announced the successful test of a nuclear device. This study provides a multi-technology analysis of the 2017 North Korean event and its aftermath using a wide array of geophysical methods (seismology, infrasound, remote sensing, radionuclide monitoring, and atmospheric transport modeling). Our results clearly indicate that the September 2017 North Korean event was in fact a nuclear test. Read more
Demystifying academics to enhance university–business collaborations in environmental science Geoscience Communication DOI 10.5194/gc-2-1-2019 15 January 2019 Worldwide there is intense interest in converting research excellence in universities into commercial success, but there has been scant attention devoted to exactly how individual scientists’ workload and incentive structures may be a key barrier to this. Our work reveals the real challenge posed by a time-constrained university culture, better describes how work with business might fit into an academic job, and gives tips on working together in anuser guidefor scientists and (re)insurers. Read more
Indian winter and summer monsoon strength over the 4.2 ka BP event in foraminifer isotope records from the Indus River delta in the Arabian Sea Climate of the Past DOI 10.5194/cp-15-73-2019 15 January 2019 A foraminifer oxygen isotope record from the northeastern Arabian Sea was used to reconstruct winter and summer monsoon strength from 5.4 to 3.0 ka. We found a 200-year period of strengthened winter monsoon (4.5–4.3 ka) that coincides with the earliest phase of the Mature Harappan period of the Indus Civilization, followed by weakened winter and summer monsoons by 4.1 ka. Aridity spanning both rainfall seasons at 4.1 ka may help to explain some of the observed archaeological shifts. Read more
Volatile organic compounds and ozone in Rocky Mountain National Park during FRAPPÉ Atmospheric Chemistry and Physics DOI 10.5194/acp-19-499-2019 14 January 2019 Rocky Mountain National Park experiences high ozone concentrations that can exceed the National Ambient Air Quality Standard. As part of the FRAPPÉ field campaign, a suite of volatile organic compounds were measured to characterize the sources of ozone precursors that contribute to high ozone in the park. These measurements indicate emissions from the Front Range in Colorado tied to oil and gas operations, urban areas, and the stratosphere contribute to episodes of elevated ozone. Read more