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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.

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