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 Hydrology and Earth System Sciences DOI 10.5194/hess-19-209-2015 14 January 2015 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. Read more
Seasonal in situ observations of glyoxal and methylglyoxal over the temperate oceans of the Southern Hemisphere Atmospheric Chemistry and Physics DOI 10.5194/acp-15-223-2015 12 January 2015 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. Read more
Internally and externally induced deformations of the magnetospheric equatorial current as inferred from spacecraft data Annales Geophysicae DOI 10.5194/angeo-33-1-2015 6 January 2015 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). Read more
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. Read more
What causes cooling water temperature gradients in a forested stream reach? Hydrology and Earth System Sciences DOI 10.5194/hess-18-5361-2014 20 December 2014 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. Read more
Processes determining the marine alkalinity and calcium carbonate saturation state distributions Biogeosciences DOI 10.5194/bg-11-7349-2014 19 December 2014 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. Read more
Dams on Mekong tributaries as significant contributors of hydrological alterations to the Tonle Sap Floodplain in Cambodia Hydrology and Earth System Sciences DOI 10.5194/hess-18-5303-2014 18 December 2014 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. Read more
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. Read more
A virtual water network of the Roman world Hydrology and Earth System Sciences DOI 10.5194/hess-18-5025-2014 11 December 2014 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. Read more
Solar irradiances measured using SPN1 radiometers: uncertainties and clues for development Atmospheric Measurement Techniques DOI 10.5194/amt-7-4267-2014 8 December 2014 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. Read more
A possible influence of the Great White Spot on Saturn kilometric radiation periodicity Annales Geophysicae DOI 10.5194/angeo-32-1463-2014 4 December 2014 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. Read more
Estimating degree-day factors from MODIS for snowmelt runoff modeling Hydrology and Earth System Sciences DOI 10.5194/hess-18-4773-2014 3 December 2014 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. Read more
Potential climate forcing of land use and land cover change Atmospheric Chemistry and Physics DOI 10.5194/acp-14-12701-2014 3 December 2014 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. Read more
Estimated stocks of circumpolar permafrost carbon with quantified uncertainty ranges and identified data gaps Biogeosciences DOI 10.5194/bg-11-6573-2014 1 December 2014 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. Read more
A comparison between VEGA 1, 2 and Giotto flybys of comet 1P/Halley: implications for Rosetta Annales Geophysicae DOI 10.5194/angeo-32-1441-2014 28 November 2014 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. Read more
Correlations between climate network and relief data Nonlinear Processes in Geophysics DOI 10.5194/npg-21-1127-2014 27 November 2014 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. Read more
Path independence of climate and carbon cycle response over a broad range of cumulative carbon emissions Earth System Dynamics DOI 10.5194/esd-5-409-2014 24 November 2014 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. Read more
Long-term trends at the Boknis Eck time series station (Baltic Sea), 1957–2013: does climate change counteract the decline in eutrophication? Biogeosciences DOI 10.5194/bg-11-6323-2014 24 November 2014 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. Read more
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. Read more
The global monsoon across timescales: coherent variability of regional monsoons Climate of the Past DOI 10.5194/cp-10-2007-2014 21 November 2014 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. Read more