Boundary layer models for calving marine outlet glaciers The Cryosphere DOI 10.5194/tc-11-2283-2017 5 October 2017 We show mathematically and computationally how discharge of ice from ocean-terminating glaciers is controlled by a combination of different forces acting on ice near the grounding line of a glacier and how that combination of forces is affected by the process of iceberg formation, which limits the length of floating ice tongues extending in front of the glacier. We show that a deeper fjord may lead to a longer ice tongue providing greater drag on the glacier, slowing the rate of ice discharge. Read more
Complex relationship between seasonal streamflow forecast skill and value in reservoir operations Hydrology and Earth System Sciences DOI 10.5194/hess-21-4841-2017 28 September 2017 This study investigates the relationship between skill and value of ensemble seasonal streamflow forecasts. Using data from a modern forecasting system, we show that skilled forecasts are more likely to provide benefits for reservoirs operated to maintain a target water level rather than reservoirs operated to satisfy a target demand. We identify the primary causes for this behaviour and provide specific recommendations for assessing the value of forecasts for reservoirs with supply objectives. Read more
The Plio-Pleistocene climatic evolution as a consequence of orbital forcing on the carbon cycle Climate of the Past DOI 10.5194/cp-13-1259-2017 25 September 2017 Ice ages are paced by astronomical parameters. On longer timescales, the astronomy also acts on climate, as evidenced by the 400 kyr signature observed in carbon isotopic records. In this paper, I present a conceptual model that links the astronomy to the dynamics of organic carbon in coastal areas. The model reproduces the carbon isotopic records and a two-step decrease in atmospheric CO2that would explain the Pleistocene (~ 2.8 Myr BP) and mid-Pleistocene (~ 0.8 Myr BP) transition. Read more
An explanation for the different climate sensitivities of land and ocean surfaces based on the diurnal cycle Earth System Dynamics DOI 10.5194/esd-8-849-2017 25 September 2017 We provide an explanation why land temperatures respond more strongly to global warming than ocean temperatures, a robust finding in observations and models that has so far not been understood well. We explain it by the different ways by which ocean and land surfaces buffer the strong variation in solar radiation and demonstrate this with a simple, physically based model. Our explanation also illustrates why nighttime temperatures warm more strongly, another robust finding of global warming. Read more
Response to Filchner–Ronne Ice Shelf cavity warming in a coupled ocean–ice sheet model – Part 1: The ocean perspective Ocean Science DOI 10.5194/os-13-765-2017 21 September 2017 A coupled model has been developed to study the interaction between the ocean and the Antarctic ice sheet. Simulations for present-day climate yield realistic ice-shelf melt rates and a grounding line position close to the observed state. In a warm-water-inflow scenario, the model suggests a substantial thinning of the ice shelf and a local retreat of the grounding line. The coupled model yields a stronger increase in ice-shelf basal melt rates than a fixed-geometry control experiment. Read more
Community climate simulations to assess avoided impacts in 1.5 and 2 ∘C futures Earth System Dynamics DOI 10.5194/esd-8-827-2017 19 September 2017 We present the results of a set of climate simulations designed to simulate futures in which the Earth’s temperature is stabilized at the levels referred to in the 2015 Paris Agreement. We consider the necessary future emissions reductions and the aspects of extreme weather which differ significantly between the 2 and 1.5 °C climate in the simulations. Read more
Combining ground-based microwave radiometer and the AROME convective scale model through 1DVAR retrievals in complex terrain: an Alpine valley case study Atmospheric Measurement Techniques DOI 10.5194/amt-10-3385-2017 18 September 2017 Microwave radiometers have the capability of observing temperature and humidity profiles with a few minute time resolution. This study investigates the potential benefit of this instrument to improve weather forecasts thanks to a better initialization of the model. Our results show that a significant improvement can be expected in the model initialization in the first 3 km with potential impacts on weather forecasts. Read more
A national-scale seasonal hydrological forecast system: development and evaluation over Britain Hydrology and Earth System Sciences DOI 10.5194/hess-21-4681-2017 15 September 2017 The research presented here provides the first evaluation of the skill of a seasonal hydrological forecast for the UK. The forecast scheme combines rainfall forecasts from the Met Office GloSea5 forecast system with a national-scale hydrological model to provide estimates of river flows 1 to 3 months ahead. The skill in the combined model is assessed for different seasons and regions of Britain, and the analysis indicates that Autumn/Winter flows can be forecast with reasonable confidence. Read more
Astronomical calibration of the Ypresian timescale: implications for seafloor spreading rates and the chaotic behavior of the solar system? Climate of the Past DOI 10.5194/cp-13-1129-2017 11 September 2017 We assembled a very accurate geological timescale from the interval 47.8 to 56.0 million years ago, also known as the Ypresian stage. We used cyclic variations in the data caused by periodic changes in Earthäs orbit around the sun as a metronome for timescale construction. Our new data compilation provides the first geological evidence for chaos in the long-term behavior of planetary orbits in the solar system, as postulated almost 30 years ago, and a possible link to plate tectonics events. Read more
An update on ozone profile trends for the period 2000 to 2016 Atmospheric Chemistry and Physics DOI 10.5194/acp-17-10675-2017 11 September 2017 Thanks to the 1987 Montreal Protocol and its amendments, ozone-depleting chlorine (and bromine) in the stratosphere has declined slowly since the late 1990s. Improved and extended long-term ozone profile observations from satellites and ground-based stations confirm that ozone is responding as expected and has increased by about 2 % per decade since 2000 in the upper stratosphere, around 40 km altitude. At lower altitudes, however, ozone has not changed significantly since 2000. Read more
Extracting real-crack properties from non-linear elastic behaviour of rocks: abundance of cracks with dominating normal compliance and rocks with negative Poisson ratios Nonlinear Processes in Geophysics DOI 10.5194/npg-24-543-2017 5 September 2017 A new method of analysing pressure wave dependences is presented and tested against the published experimental data. Upon the results of examination of more than 90 rock samples, it was found that a significant portion of rocks (~ 45 %) exhibit negative Poisson ratios at lower pressures. Such a significant number of naturally auxetic rocks suggests that the occurrence of negative Poisson ratios is not as exotic as assumed previously. Read more
JRAero: the Japanese Reanalysis for Aerosol v1.0 Geoscientific Model Development DOI 10.5194/gmd-10-3225-2017 4 September 2017 A global aerosol reanalysis product named the Japanese Reanalysis for Aerosol (JRAero) was constructed by the Meteorological Research Institute (MRI) of the Japan Meteorological Agency. The reanalysis employs a global aerosol transport model developed by MRI and a two-dimensional variational data assimilation method. It assimilates maps of aerosol optical depth (AOD) from MODIS onboard the Terra and Aqua satellites every 6 h and has a TL159 horizontal resolution (approximately 1.1° × 1.1°). Read more
The electric current approach in the solar–terrestrial relationship Annales Geophysicae DOI 10.5194/angeo-35-965-2017 21 August 2017 The sequence of phenomena consisting of solar flares, coronal mass ejections (CMEs), auroral substorm, and geomagnetic storms is mostly a manifestation of electromagnetic energy dissipation. Thus, first of all, it is natural to consider each of them in terms of a sequence of power supply (dynamo), power transmission (electric currents/circuits), and dissipation (mostly observed phenomena), i.e., as an input–output process and the electric current line approach. Read more
Simultaneous measurements of new particle formation at 1 s time resolution at a street site and a rooftop site Atmospheric Chemistry and Physics DOI 10.5194/acp-17-9469-2017 8 August 2017 This study reports the distinct effects of street canyons on new particle formation (NPF) under warm or cold ambient temperature conditions because of on-road vehicle emissions; i.e., stronger condensation sinks are responsible for the reduced NPF in the springtime, but efficient nucleation and partitioning of gaseous species contribute to the enhanced NPF in the wintertime. The oxidization of biogenic organics is suggested to play an important role in growing new particles. Read more
Has dyke development in the Vietnamese Mekong Delta shifted flood hazard downstream? Hydrology and Earth System Sciences DOI 10.5194/hess-21-3991-2017 7 August 2017 In this study we provide a numerical quantification of changes in flood hazard in the Vietnamese Mekong Delta as a result of dyke development. Other important drivers to the alteration of delta flood hazard are also investigated, e.g. tidal level. The findings of our study are substantial valuable for the decision makers in Vietnam to develop holistic and harmonized floods and flood-related issues management plan for the whole delta. Read more
NOx emission trends over Chinese cities estimated from OMI observations during 2005 to 2015 Atmospheric Chemistry and Physics DOI 10.5194/acp-17-9261-2017 1 August 2017 We assess NOx emission trends over Chinese cities based on satellite NO2 observations using a method independent of chemical transport models. NOx emissions over 48 Chinese cities have decreased significantly since 2011. Cities with different dominant emission sources (i.e. power, industrial, and transportation sectors) showed variable emission decline timelines that corresponded to the schedules for emission control in different sectors. Read more
An intercomparison of approaches for improving operational seasonal streamflow forecasts Hydrology and Earth System Sciences DOI 10.5194/hess-21-3915-2017 31 July 2017 Water supply forecasts are critical to support water resources operations and planning. The skill of such forecasts depends on our knowledge of (i) future meteorological conditions and (ii) the amount of water stored in a basin. We address this problem by testing several approaches that make use of these sources of predictability, either separately or in a combined fashion. The main goal is to understand the marginal benefits of both information and methodological complexity in forecast skill. Read more
Every apple has a voice: using stable isotopes to teach about food sourcing and the water cycle Hydrology and Earth System Sciences DOI 10.5194/hess-21-3799-2017 25 July 2017 Fruits take up soil water as they grow, and thus the fruit water is related to the rain or irrigation the crop receives. We used a novel sampling system to measure the stable isotopes of H and O in the fruit water to determine its geographic origin by comparing it to maps of isotopes in rain. We used this approach to teach an audience of science students and teachers about water cycle concepts and how humans may modify the water cycle through agriculture and irrigation water diversions. Read more
The double high tide at Port Ellen: Doodson’s criterion revisited Ocean Science DOI 10.5194/os-13-599-2017 20 July 2017 Some places experience double high tides, where the tide starts to ebb for a short while, only to briefly flood again before finally receding. The result is a very long high tide with weak currents, and is important for navigational purposes. The existing theory for when and where double high tides occur does not always capture them, and it can only be applied to double highs occurring on a twice-daily tide. Here, the criterion has been generalized to capture all double high or low tides. Read more
Reviews and syntheses: Systematic Earth observations for use in terrestrial carbon cycle data assimilation systems Biogeosciences DOI 10.5194/bg-14-3401-2017 19 July 2017 This paper briefly reviews data assimilation techniques in carbon cycle data assimilation and the requirements of data assimilation systems on observations. We provide a non-exhaustive overview of current observations and their uncertainties for use in terrestrial carbon cycle data assimilation, focussing on relevant space-based observations. Read more