ESD Ideas: Why are glaciations slower than deglaciations? Earth System Dynamics DOI 10.5194/esd-11-13-2020 23 January 2020 Here we explore ancient climate transitions from warm periods to ice ages and from ice ages to warm periods of the last 400 000 years. The changeovers from warm to ice age conditions are slower than those from ice age to warm conditions. We propose the presence of strong negative sea–ice feedbacks may be responsible for slowing the transition from warm to full ice age conditions. By improving understanding of past abrupt changes, we may have improved knowledge of future system behavior. Read more
First data set of H2O/HDO columns from the Tropospheric Monitoring Instrument (TROPOMI) Atmospheric Measurement Techniques DOI 10.5194/amt-13-85-2020 23 January 2020 This paper presents a new H 2 O/HDO data set from TROPOMI short-wave infrared measurements. It is validated against recent ground-based FTIR measurements from the TCCON network. A bias in TCCON HDO (which is not verified) is corrected by fitting a correction factor for the HDO column to match MUSICA δD for common observations. The use of the new TROPOMI data set is demonstrated using a case study of a blocking anticyclone over Europe in July 2018. Read more
Can subduction initiation at a transform fault be spontaneous? Solid Earth DOI 10.5194/se-11-37-2020 17 January 2020 We propose a new exploration of the concept of “spontaneous” lithospheric collapse at a transform fault (TF) by performing a large study of conditions allowing instability of the thicker plate using 2-D thermomechanical simulations. Spontaneous subduction is modelled only if extreme mechanical conditions are assumed. We conclude that spontaneous collapse of the thick older plate at a TF evolving into mature subduction is an unlikely process of subduction initiation at modern Earth conditions. Read more
Terrestrial ion escape and relevant circulation in space Annales Geophysicae DOI 10.5194/angeo-37-1197-2019 17 January 2020 Terrestrial ion transport and total escape are synthesized, with stress on the high-latitude polar region and the inner magnetosphere where Custer significantly improved knowledge. After estimating the outflow flux and destinations, complicated ion dynamics in the inner magnetosphere was classified and summarized, through which more than half the O+ is finally lost to space. Together with direct escapes, total O+ escape is high enough to influence the evolution of the biosphere. Read more
Seasonal partitioning of precipitation between streamflow and evapotranspiration, inferred from end-member splitting analysis Hydrology and Earth System Sciences DOI 10.5194/hess-24-17-2020 17 January 2020 Perhaps the oldest question in hydrology is “Where does water go when it rains?”. Here we present a new way to measure how the terrestrial water cycle partitions precipitation into its two ultimate fates: “green water” that is evaporated or transpired back to the atmosphere and “blue water” that is discharged to stream channels. Our analysis may help in gauging the vulnerability of both water resources and terrestrial ecosystems to changes in rainfall patterns. Read more
Two types of North American droughts related to different atmospheric circulation patterns Climate of the Past DOI 10.5194/cp-15-2053-2019 17 January 2020 The western USA is frequently affected by multiannual summer droughts. They can be separated into two groups with distinct spatial patterns. This study analyzes the atmospheric circulation during multiannual droughts in a new 3-D climate reconstruction. We confirm two distinct drought types differing with respect to atmospheric circulation as well as sea surface temperatures. Our results suggest that both the Pacific and the extratropical North Atlantic region affect North American droughts. Read more
Effectiveness of landscape decontamination following the Fukushima nuclear accident: a review SOIL DOI 10.5194/soil-5-333-2019 30 December 2019 The Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident in March 2011 resulted in the contamination of Japanese landscapes with radioactive fallout. The objective of this review is to provide an overview of the decontamination strategies and their potential effectiveness in Japan. Overall, we believe it is important to synthesise the remediation lessons learnt following the FDNPP nuclear accident, which could be fundamental if radioactive fallout occurred somewhere on Earth in the future. Read more
Generation of Rossby waves off the Cape Verde Peninsula: the role of the coastline Ocean Science DOI 10.5194/os-15-1667-2019 30 December 2019 In December 2002 and January 2003 satellite observations of chlorophyll showed a wavelike pattern with a wavelength of about 750 km south-west of the Cape Verde Peninsula. Such a pattern suggests the existence of a locally generated Rossby wave which slowly propagated westward. To verify this hypothesis a numerical study based on a simple model has been conducted. The numerical results are completed by an analytical study which evaluates the potential impact of the coastline shape. Read more
Ice-nucleating particle versus ice crystal number concentrationin altocumulus and cirrus layers embedded in Saharan dust:a closure study Atmospheric Chemistry and Physics DOI 10.5194/acp-19-15087-2019 30 December 2019 For the first time, a closure study of the relationship between the ice-nucleating particle concentration (INPC) and ice crystal number concentration (ICNC) in altocumulus and cirrus layers, solely based on ground-based active remote sensing, is presented. The closure studies were conducted in Cyprus. A focus was on altocumulus and cirrus layers which developed in pronounced Saharan dust layers. The closure studies show that heterogeneous ice nucleation can play a dominant role in ice formation. Read more
Understanding snow bedform formation by adding sintering to a cellular automata model The Cryosphere DOI 10.5194/tc-13-3239-2019 17 December 2019 Snow surfaces, under the action of wind, form beautiful shapes such as waves and dunes. This study is the first ever study to simulate these shapes using a state-of-the-art numerical modelling tool. While these beautiful and ephemeral shapes on snow surfaces are fascinating from a purely aesthetic point of view, they are also critical in regulating the transfer of heat and mass between the atmosphere and snowpacks, thus being of huge importance to the Earth system. Read more
A comparative assessment of the uncertainties of global surface ocean CO2 estimates using a machine-learning ensemble (CSIR-ML6 version 2019a) – have we hit the wall? Geoscientific Model Development DOI 10.5194/gmd-12-5113-2019 17 December 2019 The ocean plays a vital role in mitigating climate change by taking up atmospheric carbon dioxide (CO2). Historically sparse ship-based measurements of surface ocean CO2make direct estimates of CO2exchange changes unreliable. We introduce a machine-learning ensemble approach to fill these observational gaps. Our method performs incrementally better relative to past methods, leading to our hypothesis that we are perhaps reaching the limitation of machine-learning algorithms’ capability. Read more
On the seasonal variation in observed size distributions in northern Europe and their changes with decreasing anthropogenic emissions in Europe: climatology and trend analysis based on 17 years of data from Aspvreten, Sweden Atmospheric Chemistry and Physics DOI 10.5194/acp-19-14849-2019 17 December 2019 In this study we explore 17 years of aerosol number size distribution data (10–390 nm) observed at Aspvreten (58.8° N, 17.4° E, 25 m a.s.l.). The station, located in northern Europe, is representative of rural background conditions. The study focused on identifying trends in aerosol number size distribution properties. The study shows that total number has decreased by 30 % and aerosol submicron mass by 50 % on average. Observed trends vary strongly with both season and particle size. Read more
Stepwise chemical abrasion–isotope dilution–thermal ionization mass spectrometry with trace element analysis of microfractured Hadean zircon Geochronology DOI 10.5194/gchron-1-85-2019 17 December 2019 The oldest known minerals on Earth are Hadean (> 4.0 Ga) zircons from the Jack Hills, Australia. We present the first application to such Hadean zircons of stepwise chemical abrasion–isotope dilution–thermal ionization mass spectrometry with trace element analysis (stepwise CA-ID-TIMS-TEA). We examine the evolution in the U–Pb age and trace element chemistry of zircon domains accessed by successive chemical abrasion steps in the context of the geologic history of the Jack Hills zircons. Read more
Societal breakdown as an emergent property of large-scale behavioural models of land use change Earth System Dynamics DOI 10.5194/esd-10-809-2019 10 December 2019 Concerns are growing that human activity will lead to social and environmental breakdown, but it is hard to anticipate when and where such breakdowns might occur. We developed a new model of land management decisions in Europe to explore possible future changes and found that decision-making that takes into account social and environmental conditions can produce unexpected outcomes that include societal breakdown in challenging conditions. Read more
First reported case of thunderstorm asthma in Israel Natural Hazards and Earth System Sciences DOI 10.5194/nhess-19-2715-2019 10 December 2019 During severe thunderstorms, cold outflows can eject pollen and dust particles from the surface, releasing allergens and causingthunderstorm asthmaepidemics in sensitive populations. We report the first case in Israel that occurred on 25 October 2015. The emergency room presentation records from three hospitals in central Israel showed a clear increase in patients with respiratory complaints immediately after the passage of a massive super-cell thunderstorm in the area. Read more
The diurnal cycle of the smoky marine boundary layer observed during August in the remote southeast Atlantic Atmospheric Chemistry and Physics DOI 10.5194/acp-19-14493-2019 10 December 2019 Boundary layer (BL) semi-direct effects in the remote SE Atlantic are investigated using LASIC field measurements and satellite retrievals. Low-cloud cover and cloud liquid water path decrease with increasing smoke loadings in the BL. Daily-mean surface-based mixed layer is warmer by 0.5 K, moisture accumulates near the surface throughout the night, and the BL deepens by 200 m, with LWPs and cloud top heights increasing, in the sunlit morning hours, as part of the smoke-altered BL diurnal cycle. Read more
Can we use sea surface temperature and productivity proxy records to reconstruct Ekman upwelling? Climate of the Past DOI 10.5194/cp-15-1985-2019 10 December 2019 We test two assumptions that are often made in paleoclimate studies by using observations and ask whether temperature and productivity proxy records in the Southern California Current can be used to reconstruct Ekman upwelling. By examining the covariation between alongshore wind stress, temperature, and productivity, we found that the dominant covarying pattern does not reflect Ekman upwelling. Other upwelling patterns found are timescale dependent. Multiple proxies can improve reconstruction. Read more
Large-scale particulate air pollution and chemical fingerprint of volcanic sulfate aerosols from the 2014–2015 Holuhraun flood lava eruption of Bárðarbunga volcano (Iceland) Atmospheric Chemistry and Physics DOI 10.5194/acp-19-14253-2019 3 December 2019 This study, benefiting especially from recently developed mass spectrometry observations of aerosols, highlights unknown properties of volcanic sulfates in the troposphere. It shows their specific chemical fingerprint, distinct from those of freshly emitted industrial sulfates and background aerosols. We also demonstrate the large-scale persistence of the volcanic sulfate pollution over weeks. Hence, these results cast light on the impact of tropospheric eruptions on air quality and climate. Read more
Low-temperature triple-capillary cryostat for ice crystal growth studies Atmospheric Measurement Techniques DOI 10.5194/amt-12-6143-2019 3 December 2019 We have built a triple-capillary cryostat designed to reduce potential instrumental effects that may have influenced earlier measurements and to improve our understanding of the processes responsible for ice crystal shapes and sizes. In this cryostat, a crystal forms on one of three well-separated and ultrafine capillaries. In this paper we describe the new instrument and present several observations made using the instrument to illustrate the instrument’s advantages. Read more
Compacting the description of a time-dependent multivariable system and its multivariable driver by reducing the state vectors to aggregate scalars: the Earth’s solar-wind-driven magnetosphere Nonlinear Processes in Geophysics DOI 10.5194/npg-26-429-2019 3 December 2019 A methodology is developed to simplify the mathematical description of activity in a time-dependent driven system. The method describes the response in the system that is most-closely related to the driver. This reduced description has advantages: low noise, high prediction efficiency, linearity in the described system response to the driver, and compactness. The analysis of the Earth’s magnetospheric system is demonstrated. Read more