The Differential Warming Response of Britain's Rivers (1982-2011)

River water temperature is a hydrological feature primarily controlled by topographical, meteorological, climatological, and anthropogenic factors. For Britain, the study of freshwater temperatures has focussed mainly on observations made in England and Wales; similar comprehensive data sets for Scotland are currently unavailable. Here we present a model for the whole of mainland Britain over three recent decades (1982-2011) that incorporates geographical extrapolation to Scotland. The model estimates daily mean freshwater temperature for every river segment and for any day in the studied period, based upon physico-geographical features, daily mean air and sea temperatures, and available freshwater temperature measurements. We also extrapolate the model temporally to predict future warming of Britain's rivers given current observed trends. Our results highlight the spatial and temporal diversity of British freshwater temperatures and warming rates. Over the studied period, Britain's rivers had a mean temperature of 9.84°C and experienced a mean warming of +0.22°C per decade, with lower rates for segments near lakes and in coastal regions. Model results indicate April as the fastest-warming month (+0.63°C per decade on average), and show that most rivers spend on average ever more days of the year at temperatures exceeding 10°C, a critical threshold for several fish pathogens. Our results also identify exceptional warming in parts of the Scottish Highlands (in April and September) and pervasive cooling episodes, in December throughout Britain and in July in the southwest of England (in Wales, Cornwall, Devon, and Dorset). This regional heterogeneity in rates of change has ramifications for current and future water quality, aquatic ecosystems, as well as for the spread of waterborne diseases

Earth's magnetic field in the early 19th century from French sources

International audienceWe present both a description of a new magnetic data set covering predominantly the 18th and 19th centuries and the results derived from it for the small window 1820-1850, from which the bulk of the data originate. The data set comprises measurements of declination taken overwhelmingly on French naval and hydrographic vessels. A list of the vessels is given for one of the data sets. When augmented by extant inclination measurements, the data are capable of resolving the magnetic field at the core-mantle boundary to a high degree of fidelity and thus are a valuable addition to the data set of historical geomagnetic measurements

Modelled British river water temperatures (1982-2011)

River water temperature model ctrBR8211a for the whole of mainland Britain over three decades (1982-2011) estimates daily mean freshwater temperatures for 20,578 coastal, lacustrine, and riverine segments, defined in the EEA's ECRINS dataset. Its construction incorporates geographical features, daily mean air and sea temperatures, and freshwater temperature measurements. Its timespan captures general warming trends (+0.22 ⁰C/decade, lower for lakes and coasts), identifies April as the fastest-warming month (+0.63 ⁰C/decade), and shows that most rivers spend on average ever longer at temperatures exceeding 10 ⁰C. Plotted geographically, local warming rates delineate seasonally- and monthly-varying regions with distinct thermal properties, including exceptional warming in the Scottish Highlands (in April and September) and pervasive cooling episodes in December throughout Britain and in July in the southwest (in Wales, Cornwall, Devon, and Dorset). This dataset provides a river segments database, time series per segment, two data visualisation utilities, and auxiliary files

Modelled rates of change in annual mean water temperature for Britain’s rivers in 1982–2011.

<p>The 20,578 British river segments show large geographical differences in warming response. Central England, the east coast and Yorkshire regions experienced the highest rates, whereas Cumbria and parts of Wales have the lowest. The Scottish Highlands show lowest annual warming response overall, but with notable exceptions (lochs Cluanie, Rannoch, and Katrine) that reflect local anomalies in air temperature there. Cylindrical equal-area projection. Scottish model results extrapolate English and Welsh data.</p

Modelled rates of change in seasonal mean water temperature for Britain’s rivers in 1982–2011.

<p>(A) the meteorological spring displays the highest mean warming rate (mean: +0.041°C/yr) in rivers throughout Britain; (B) Summer (mean: +0.013°C/yr) has the broadest range of rates, from -0.048 to +0.050°C/yr; (C) Autumn’s warming rates (mean: +0.031°C/yr) are lower than Spring’s, but higher than in Summer; (D) Winter is anomalous, with large parts of Britain exhibiting freshwater cooling, and a mean warming rate only marginally above zero. Cylindrical equal-area projection. Scottish model results extrapolate English and Welsh data.</p

The four publicly available data sets used in this study.

<p>The four publicly available data sets used in this study.</p