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Intercomparison of vertically resolved merged satellite ozone data sets: interannual variability and long-term trends

Understanding ozone trends in the vertical are vital in terms of assessing the success of the Montreal Protocol. This paper compares and analyses the long-term trends in stratospheric ozone from seven new merged satellite data sets. The data sets largely agree well with each other, particularly for the negative trends seen in the early period 1984-1997. For the 1998-2011 period there is less agreement, but a clear shift from negative to mostly positive trends.

Continuous and discontinuous variation in ecosystem carbon stocks with elevation across a treeline ecotone

Here we investigate how ecosystem carbon stocks vary with elevation shifting from the closed forest to open alpine tundra, in the mountains of southern Norway. Above-ground carbon stocks decreased with elevation, with a clear breakpoint at the forest line, while the organic horizon soil carbon stocks increased linearly with elevation. Overall, ecosystem carbon stocks increased with elevation above the treeline and decreased with elevation below, demonstrating the importance of the treeline.

A novel algorithm for detection of precipitation in tropical regions using PMW radiometers

The CCA algorithm is applicable to any modern passive microwave radiometer on board polar orbiting satellites; it has been developed using a data set of co-located SSMIS and TRMM~~PR measurements and AMSU~~MHS and TRMM-PR measurements. The algorithm shows a small rate of false alarms and superior detection capability and can efficiently detect (POD between 0.55 and 0.71) minimum rain rate varying from 0.14 mm/h (AMSU over ocean) to 0.41 (SSMIS over coast).

The soil N cycle: new insights and key challenges

SOIL
DOI 10.5194/soil-1-235-2015
11 March 2015

Here, we review important insights with respect to the soil N cycle that have been made over the last decade, and present a personal view on the key challenges of future research.

Improved routines to model the ocean carbonate system: mocsy 2.0

We provide improved routines to model the ocean carbonate system, i.e., to compute ocean pH and related variables from dissolved inorganic carbon and total alkalinity. These routines (1) rely on the fastest available algorithm to solve the alkalinity-pH equation, which converges even under extreme conditions; (2) avoid common model approximations that lead to errors of 3% or more in computed variables; and (3) account for large pressure effects on subsurface pCO2, unlike other packages.

Use of Ra isotopes to deduce rapid transfer of sediment-derived inputs off Kerguelen

We investigated the origin and mechanisms of the natural iron fertilization that sustains a phytoplankton bloom downstream of the Kerguelen Islands. We used radium isotopes to trace the fate of shelf waters that may transport iron and other micronutrients towards offshore waters. We show that shelf waters are rapidly transferred offshore and may be transported across the polar front (PF). The PF may thus not be a strong physical barrier for chemical elements released by the shelf sediments.

Using results from the PlioMIP ensemble to investigate the Greenland Ice Sheet during the mid-Pliocene Warm Period

Climate and ice sheet models are often used to predict the nature of ice sheets in Earth history. It is important to understand if such predictions are consistent between different models, especially in warm periods of relevance to the future. We use input from 15 different climate models to run one ice sheet model and compare the predictions over Greenland. We find that there are large differences between the predicted ice sheets for the warm Pliocene (c. 3 million years ago).

Evaluation of coral reef carbonate production models at a global scale

Production of calcium carbonate by coral reefs is important in the global carbon cycle. Using a global framework we evaluate four models of reef calcification against observed values. The temperature-only model showed significant skill in reproducing coral calcification rates. The absence of any predictive power for whole reef systems highlights the importance of coral cover and the need for an ecosystem modelling approach accounting for population dynamics in terms of mortality and recruitment.

Does temperature affect the accuracy of vented pressure transducer in fine-scale water level measurement?

Geoscientific Instrumentation, Methods and Data Systems
DOI 10.5194/gi-4-65-2015
3 March 2015

This paper discussed the effect of temperature on the accuracy of submersible strain gauge pressure transducers. The results show that rapid change of temperature introduces errors in the water level reading while the absolute temperature is also related to the sensor errors. The former is attributed to venting and the latter is attributed to temperature compensation effects in the strain gauges. Performance tests are necessary before field deployment to ensure the data quality.

Persistent after-effects of heavy rain on concentrations of ice nuclei and rainfall suggest a biological cause

We show that atmospheric load of ice nuclei is enhanced for up to 20 days after key rainfall events. The rate of enhancement decreases exponentially with time. Rainfall quantity and frequency are increased for a similar duration and with similar exponential decreases thereby supporting the notion of rainfall feedback. We reveal series of significant feedback in rainfall patterns across Australia over the past century and marked changes in feedback patterns, and we indicate their locations.

Quantitative high-resolution observations of soil water dynamics in a complicated architecture using time-lapse ground-penetrating radar

In this study, we analyze a set of high-resolution, surface-based, 2-D Ground-Penetrating Radar (GPR) observations of artificially induced subsurface water dynamics. In particular, we place close scrutiny on the evolution of the capillary fringe in a highly dynamic regime with surface based time-lapse GPR. We thoroughly explain all observed phenomena based on theoretical soil physical considerations and numerical simulations of both subsurface water flow and the expected GPR response.

Identification and quantification of gaseous organic compounds emitted from biomass burning using two-dimensional gas chromatography–time-of-flight mass spectrometry

This work represents the first application of two-dimensional gas chromatography to broadly characterize the gas-phase emissions of biomass burning, including comparisons among the emissions from burns of selected conifer, grass, crop residue, and peat fuel types. In these smoke samples, over 700 compounds were detected, which are discussed in the context of potential secondary organic aerosol formation.

A 3-D shear velocity model of the southern North American and Caribbean plates from ambient noise and earthquake tomography

Solid Earth
DOI 10.5194/se-6-271-2015
20 February 2015

We compute a velocity model of the crust and uppermost mantle of Southern North America, Mexico and the Caribbean. We use a recent technique based on ‘ambient noise’ – or continuous seismic records – and a traditional one using earthquakes. Both techniques, together with the increased number of seismic stations in the region, allow us to obtain greater resolution than previous works. Some of its applications are to localize regional earthquakes and simulate ground motions.

Drought in forest understory ecosystems – a novel rainfall reduction experiment

Biogeosciences
DOI 10.5194/bg-12-961-2015
17 February 2015

This paper introduces a novel rainfall reduction experiment to investigate drought effects on soil-forest-understory-ecosystems. An annual drought with a return period of 40 years was imposed, while other ecosystem variables (humidity, air & soil temperature) remained unaffected. The first year of drought showed considerable changes in soil moisture dynamics, which affected leaf stomatal conductance of understory species as well as evapotranspiration rates of the forest understory ecosystem.

Ancient pre-glacial erosion surfaces preserved beneath the West Antarctic Ice Sheet

We use ice penetrating radar data to identify a laterally continuous, gently sloping topographic block, comprising two surfaces separated by a distinct break in slope, preserved beneath the Institute and Möller Ice Streams, West Antarctica. We interpret these features as extensive erosion surfaces, showing that ancient (pre-glacial) surfaces can be preserved at low elevations beneath ice sheets. Different erosion regimes (e.g. fluvial and marine) may have formed these surfaces.

Global trends in extreme precipitation: climate models versus observations

We present a systematic comparison of changes in historical extreme precipitation in station observations (HadEX2) and 15 climate models from the CMIP5 (as the largest and most recent sets of available observational and modeled datasets), on global and continental scale for 1901-2010, using both parametric (linear regression) and non-parametric (the Mann-Kendall as well as Sen’s slope estimator) methods, taking care to spatially and temporally sample observations and models in comparable ways.

Simulated anthropogenic CO₂ storage and acidification of the Mediterranean Sea

Biogeosciences
DOI 10.5194/bg-12-781-2015
10 February 2015

Different observational-based estimates of CO₂ uptake and resulting acidification of the Mediterranean Sea vary widely. A new study finds that even the smallest of those is an upper limit because the approach used assumes air-sea CO₂ equilibrium. Then along with a lower limit from new fine-scale numerical model simulations, the authors bracket Mediterranean Sea CO₂ uptake and acidification rates. They conclude that its rate of surface acidifcation is much like that for typical ocean waters.

A high-resolution global-scale groundwater model

In this paper we present a high resolution global-scale groundwater model of an upper aquifer. An equilibrium water table at its natural state is contructed. Aquifer parameterization is based on available global-datasets on lithology and conductivity combined with estimated aquifer thickness. The results showed groundwater levels are well simulated for many regions of the world. Simulated flow paths showed the relevance of including lateral groundwater flows in global scale hydrological models.

Technical Note: Maximising accuracy and minimising cost of a potentiometrically regulated ocean acidification simulation system

This article describes a low-cost, easy set-up, ocean acidification simulation system that reliably mimics the effects of elevated atmospheric carbon dioxide on seawater chemistry. The accessible design of this system, along with our suggestions for the validation of pH control and characterisation of seawater chemistry, will enable researchers on a limited budget to generate high quality, repeatable data documenting the response of marine organisms to ocean acidification.

Simulating the Greenland ice sheet under present-day and palaeo constraints including a new discharge parameterization

Ice discharge into the ocean from outlet glaciers is an important component of mass loss of the Greenland ice sheet. Here, we present a simple parameterization of ice discharge for coarse resolution ice sheet models, suitable for large ensembles or long-term palaeo simulations. This parameterization reproduces in a good approximation the present-day ice discharge compared with estimates, and the simulation of the present-day ice sheet elevation is considerably improved.

Permafrost soils and carbon cycling

SOIL
DOI 10.5194/soil-1-147-2015
5 February 2015

The huge carbon stocks found in soils of the permafrost region are important to the global climate system because of their potential to decompose and release greenhouse gases into the atmosphere upon thawing. This review highlights permafrost characteristics, the influence of cryogenic processes on soil formation, organic carbon accumulation and distribution in permafrost soils, the vulnerability of this carbon upon permafrost thaw, and the role of permafrost soils in a changing climate.

Glacier-surge mechanisms promoted by a hydro-thermodynamic feedback to summer melt

Here we present continuous GPS measurements and satellite synthetic-aperture-radar-based velocity maps from Basin-3, the largest drainage basin of the Austfonna ice cap, Svalbard. Our observations demonstrate strong links between surface-melt and multiannual ice-flow acceleration.

Three-dimensional morphology of equatorial plasma bubbles deduced from measurements onboard CHAMP

Total electron content (TEC) between Low-Earth-Orbit (LEO) satellites and the Global Navigation Satellite System (GNSS) satellites can be used to constrain three-dimensional morphology of equatorial plasma bubbles (EPBs). TEC gradient observed along the LEO track is strongest when the corresponding GNSS satellite is located equatorward and westward of the LEO satellite. This anisotropy supports the idea that EPBs have three-dimensional shell structures.

A reduced-complexity model for river delta formation – Part 1: Modeling deltas with channel dynamics

In this work we present DeltaRCM, a reduced-complexity model for river delta formation. It is a rule-based cellular morphodynamic model, in contrast to reductionist models based on detailed computational fluid dynamics. DeltaRCM is able to resolve channel dynamics, and to produce stratigraphy. We also explain the meaning of complexity reduction, especially what are the essential processes to be included in modeling deltas.

The fate of seeds in the soil: a review of the influence of overland flow on seed removal and its consequences for the vegetation of arid and semiarid patchy ecosystems

SOIL
DOI 10.5194/soil-1-131-2015
26 January 2015

Since seeds are the principle means by which plants move across the landscape, the final fate of seeds plays a fundamental role in the origin, maintenance, functioning and dynamics of plant communities. In arid and semiarid patchy ecosystems, where seeds are scattered into a heterogeneous environment and intense rainfalls occur, the transport of seeds by runoff to new sites represents an opportunity for seeds to reach more favourable sites for seed germination and seedling survival.

ERA-Interim/Land: a global land surface reanalysis data set

ERA-Interim/Land is a global land-surface reanalysis covering the period 1979–2010. It describes the evolution of soil moisture, soil temperature and snowpack. ERA-Interim/Land includes a number of parameterization improvements in the land surface scheme with respect to the original ERA-Interim and a precipitation bias correction based on GPCP. A selection of verification results show the added value in representing the terrestrial water cycle and its main land surface storages and fluxes.

The interdisciplinary nature of SOIL

SOIL
DOI 10.5194/soil-1-117-2015
16 January 2015

This paper provides a brief accounting of some of the many ways that the study of soils can be interdisciplinary, therefore giving examples of the types of papers we hope to see submitted to SOIL.

Experimental test of the ρ(1-α) evolution for rotational discontinuities: cluster magnetopause observations

Rotational discontinuities (RDs) in plasma allow a magnetic connection between different plasma regimes. One of their defining relations describes a balance between changes in plasma mass density and pressure anisotropy. The paper uses the high time resolution data from the Cluster satellites to directly test that relation at the terrestrial magnetopause, when standard analysis predicts that this boundary behaves like an RD. The experimental evidence shows that the said relation is not fulfilled.

Development of a large-sample watershed-scale hydrometeorological data set for the contiguous USA: data set characteristics and assessment of regional variability in hydrologic model performance

The focus of this paper is to (1) present a community dataset of daily forcing and hydrologic response data for 671 unimpaired basins across the contiguous United States that spans a very wide range of hydroclimatic conditions; and (2) provide a calibrated model performance benchmark using a common conceptual snow and hydrologic modeling system. This benchmark provides a reference level of model performance across a very large basin sample and highlights regional variations in performance.

Seasonal in situ observations of glyoxal and methylglyoxal over the temperate oceans of the Southern Hemisphere

Glyoxal and methylglyoxal are short-lived organic trace gases and important precursors of secondary organic aerosol. Measurements over oceans are sparse. We present the first in situ glyoxal and methylglyoxal observations over remote temperate oceans, alongside observations of precursor gases. Precursor gases cannot explain observed mixing ratios, highlighting an unknown source. We show a large discrepancy between calculated vertical column densities of glyoxal and those retrieved by satellite.

Internally and externally induced deformations of the magnetospheric equatorial current as inferred from spacecraft data

A new quantitative model of the global shape of the neutral sheet in the Earth’s magnetosphere is developed, parameterized by the dipole tilt, solar wind pressure, and IMF By and Bz. The model is based on data from the Polar, Cluster, Geotail, and Themis satellites taken in 1995-2013. The paper quantifies and further explains our earlier finding of the bowl-shaped deformation of the neutral sheet due to the Earth’s dipole tilt (Tsyganenko and Andreeva, GRL, v.41(4), 2014).

Soil properties and pre-Columbian settlement patterns in the Monumental Mounds Region of the Llanos de Moxos, Bolivian Amazon

SOIL
DOI 10.5194/soil-1-65-2015
6 January 2015

In the present paper we explore to what degree soil properties might have influenced pre-Columbian settlement patterns in the Monumental Mounds Region (MMR) of the Llanos de Moxos (LM), Bolivian Amazon. This study provides new data on the soil properties of the south-eastern Bolivian Amazon and reinforces the hypothesis that environmental constraints and opportunities exerted an important role on pre-Columbian occupation patterns and the population density reached in the Bolivian Amazon.

What causes cooling water temperature gradients in a forested stream reach?

This study demonstrates the processes by which instantaneous longitudinal water temperature gradients may be generated in a stream reach that transitions from moorland to semi-natural forest in the absence of substantial groundwater inflows. Water did not cool as it flowed downstream. Instead, temperature gradients were generated by a combination of reduced rates of heating in the forested reach and advection of cooler (overnight and early morning) water from the upstream moorland catchment.

Processes determining the marine alkalinity and calcium carbonate saturation state distributions

We examine and discuss the portion of ocean alkalinity that varies in response to carbonate cycling and riverine alkalinity inputs using a new tracer, Alk*. We use this tracer to quantify the controls on marine carbonate saturation: At depth, we find carbonate cycling to be a minor control relative to organic matter cycling and pressure changes. In well-equilibrated surface water, we find carbonate cycling to be less important than temperature changes and freshwater cycling.

Dams on Mekong tributaries as significant contributors of hydrological alterations to the Tonle Sap Floodplain in Cambodia

Hydrological modeling and assessment tools were used to provide evidence of the expected hydrological alterations that hydropower development in the lower Mekong tributaries could bring to the Tonle Sap. The most significant alterations are in terms of water levels during the dry season and rates of water level rise/drop which are crucial for tree seed germination and fish migrations, and therefore major ecological disruptions are likely to follow.

Estimating the volume of glaciers in the Himalayan–Karakoram region using different methods

The Cryosphere
DOI 10.5194/tc-8-2313-2014
12 December 2014

Existing methods (area-volume relations, a slope-dependent volume estimation method, and two ice-thickness distribution models) are used to estimate the ice reserves stored in Himalayan-Karakoram glaciers. Resulting volumes range from 2955–4737 km³. Results from the ice-thickness distribution models agree well with local measurements; volume estimates from area-related relations exceed the estimates from the other approaches. Evidence on the effect of the selected method on results is provided.

A virtual water network of the Roman world

Our virtual water network of the Roman World shows that virtual water trade and irrigation provided the Romans with resilience to interannual climate variability. Virtual water trade enabled the Romans to meet food demands from regions with a surplus. Irrigation provided stable water supplies for agriculture, particularly in large river catchments. However, virtual water trade also stimulated urbanization and population growth, which eroded Roman resilience to climate variability over time.

Solar irradiances measured using SPN1 radiometers: uncertainties and clues for development

This work presents a comprehensive study of SPN1 radiometers accuracy and sources of uncertainty, drawing on laboratory experiments, numerical modelling and comparison studies between measurements from this sensor and state-of-the art instruments for six diverse sites. Several clues are provided for improving the SPN1 accuracy and agreement with state-of-the art measurements.

A possible influence of the Great White Spot on Saturn kilometric radiation periodicity

In this paper we show that the large thunderstorm called Great White Spot, which raged for about 9 months in Saturn’s troposphere in 2010/2011, was accompanied by changes in the periodicity and phasing of auroral radio emissions. We suggest that the thunderstorm was a source of intense gravity waves causing a global change in Saturn’s ionospheric winds via energy and momentum deposition. This supports the theory that Saturn’s magnetospheric periodicities are driven by the upper atmosphere.

Estimating degree-day factors from MODIS for snowmelt runoff modeling

In this paper, we propose a new method for estimating the snowmelt degree-day factor (DDFS) directly from MODIS snow covered area and ground-based snow depth data without calibration. Snow density is estimated as the ratio between observed precipitation and changes in the snow volume for days with snow accumulation. DDFS values are estimated as the ratio between changes in the snow water equivalent and difference between the daily temperature and a threshold value for days with snowmelt.

Potential climate forcing of land use and land cover change

While climate change mitigation policy often focuses on the energy sector, we find that 40% of the historical human-caused change in the Earth’s radiative balance can be attributed to land use activities, such as deforestation and agriculture. Since pressure on land resources is expected to increase, we compute a theoretical upper bound on the radiative balance impacts from future land use which suggests that not only energy policy but land policy is necessary to minimize future climate change.

Estimated stocks of circumpolar permafrost carbon with quantified uncertainty ranges and identified data gaps

This study provides an updated estimate of organic carbon stored in the northern permafrost region. The study includes estimates for carbon in soils (0 to 3 m depth) and deeper sediments in river deltas and the Yedoma region. We find that field-data is still scarce from many regions. Total estimated carbon storage is ~1300 Pg with an uncertainty range of between 1100 to 1500 Pg. Around 800 Pg carbon is perennially frozen, equivalent to all carbon dioxide currently in the Earths atmosphere.

A comparison between VEGA 1, 2 and Giotto flybys of comet 1P/Halley: implications for Rosetta

We discuss three flybys (within a time span of 8 days) of comet 1P/Halley by VEGA 1, 2 and Giotto. Looking at two different plasma phenomena: mirror mode waves and field line draping; we study the differences in SW-comet interaction between these three flybys. We find that on this time scale (comparable to Rosetta’s orbits) there is a significant difference, both caused by changing outgassing rate of the comet and changes in the solar wind. We discuss implications for Rosetta RPC observations.

Correlations between climate network and relief data

In the past few years, complex networks have been extensively applied to climate sciences, yielding the new field of climate networks. Here, we generalize climate network analysis by investigating the influence of altitudes in network topology. More precisely, we verified that nodes group into different communities corresponding to geographical areas with similar relief properties. This new approach may contribute to obtaining more complete climate network models.

Path independence of climate and carbon cycle response over a broad range of cumulative carbon emissions

Recent studies have identified an approximately proportional relationship between global warming and cumulative carbon emissions. This relationship – referred to as the transient climate response to cumulative carbon emissions (TCRE) – is useful for climate policy applications. We show that the TCRE is constant for cumulative emissions lower than ~1500 GtC, but declines for higher cumulative emissions. We also find the TCRE to decrease with increasing emission rate.

Long-term trends at the Boknis Eck time series station (Baltic Sea), 1957–2013: does climate change counteract the decline in eutrophication?

A time series of 9 oceanic parameters from the coastal time series station Boknis Eck (BE, South Western Baltic Sea) in the period of 1957-2013 is analysed with respect to seasonal cycles and longterm trends. Most striking was a paradoxical decreasing trend in oxygen with a simultaneous decline in eutrophication. Possible reasons for this paradox, e.g. processes related to warming temperatures such as increased decomposition of organic matter or altered ventilation, are discussed.

Detailed ice loss pattern in the northern Antarctic Peninsula: widespread decline driven by ice front retreats

The Cryosphere
DOI 10.5194/tc-8-2135-2014
24 November 2014

This study of one of the most rapidly changing glacier regions on Earth – the Antarctic Peninsula – uses two types of satellite data to measure the rates of ice loss in detail for the individual glaciers. The satellite data is laser altimetry from ICESat and stereo image DEM differences. The results show that 24..9 ± 7.8 billion tons of ice are lost from the region north of 66°S on the Peninsula each year. The majority of the data cover 2003-2008.

The global monsoon across timescales: coherent variability of regional monsoons

It remains a debated issue as to what extent and at which timescales the global monsoon can be viewed as a major mode of climate variability. For this purpose, a PAGES (Past Global Changes) working group (WG) was set up to investigate the concept of the global monsoon and its future research directions. The WG’s synthesis is presented here.

Complex networks for streamflow dynamics

This study introduces the theory of networks, and in particular complex networks, to examine connections in streamflow dynamics. Monthly streamflow data from a network of 639 stations in the United States are studied. The connections are examined primarily using the concept of clustering coefficient, which quantifies the network’s tendency to cluster. The clustering coefficient analysis is performed with several different threshold levels based on correlations in streamflow between the stations.

Missing SO₂ oxidant in the coastal atmosphere? – observations from high-resolution measurements of OH and atmospheric sulfur compounds

Sulfuric acid plays a major role in the formation of aerosol particles and clouds. Measurements at the west coast of Ireland reveal that oxidation of SO₂ by OH explains only 20%, on average, of H₂SO₄ formation in coastal marine air. Additional sources may be oxidation by Criegee intermediates produced photolytically and/or formation from SO₃ instead of SO₂ in the oxidation of dimethyl sulfide suggesting an important role of marine emissions in the self-cleaning power of the atmosphere.