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Abstract: When planning the acquisition of new palaeo proxy data for reconstructing past climates, many factors influence the decision of where the proxies are to be collected. One such influence is the likelihood of recording a significant climate change relative to the modern. Another consideration, which is less often considered, is the desire to target regions in which there is significant uncertainty in numerical model predictions of past climate change. New proxy data in these regions enables a more rigorous test of model simulations, and results in better constraints on the various boundary conditions used to force the models. In this paper we present a methodology for targeting new palaeo proxy data, based on model simulations. We use the terrestrial late Miocene (11.6 to 5.3 Ma) as a case study. The late Miocene climate provides insights into future climate behavior, as it is believed to have been considerably warmer than the modern. We carry out a suite of late Miocene atmosphere-only General Circulation Model simulations, which we initially evaluate relative to an example dataset of terrestrial temperature and precipitation. In terms of targeting future data acquisition, we locate those regions in the model which exhibit the largest change in temperature and/or precipitation relative to the pre-industrial. We also locate those regions which display the largest variability between the model simulations, because new data in these regions are most likely to provide a strict test of the reliability of the model results. Among other regions, the Amazon basin, the Chad basin, central Canada, and northern India are identified as potentially useful areas to collect data. [Copyright &y& Elsevier]

Abstract: This paper offers an alternative to the use of geomorphological and sedimentological evidence for the reconstruction of flood and low flow frequencies. It is based on a technique developed to estimate the hydrological impact of future climate change and it uses either observed or calculated meteorological parameters. It is possible to use this method directly without modification to ‘hindcast’ events within the period of regional meteorological records, which in areas like the UK extend back over the last 150 years. It should also be possible to extend the approach to earlier periods using reconstructed meteorological parameters based on surrogate data, such as ships'' logs. The resulting extreme flow sequences may be used to study past hydrological regimes or to improve estimates of present-day risks by extending the flow records. The technique uses an airflow index-based stochastic weather generator to create hydrometeorological parameters to input into a physically based hydrological simulation model. The method is illustrated here in a reconstruction of daily flow series for the River Wye catchment above Rhayader, mid-Wales, for the period 1889–1998. The method makes use of observed climatic variables for the entire period, with the aim of capturing actual climate variability occurring over the 110-year period. Changes in high flow characteristics are assessed using the mean annual flood (MAF), Q 5 flow and peaks-over-threshold (POT) calculated from the 110-year simulated daily flow series. This particular application shows evidence of a possible trend towards increasing magnitude and frequency of high flow events, which, if continued, would have implications for flood and water resource management. Looking at evidence from the last 110 years helps to place possible future trends within the context of past variations in high flow extremes due to both natural and anthropogenically influenced fluctuations in climate. [Copyright &y& Elsevier]

Abstract: Conceptual models linking climate change with fluctuations in fish population abundances are based on how cyclic patterns in air–sea interactions influence pelagic food web dynamics. The effect of changing mixed layer dynamics on phytoplankton light and nutrient exposure is a prominent focal point in the overall mechanism. The Extended Reconstruction (ER) of Sea Surface Temperature (SST) version one (ERSSTv1) and version two (ERSSTv2) monthly time series from 1854 to 2003, interpreted with the aid of a historically based global Nitrate Depletion Temperature (NDT) climatology, provide a qualitative tool for examining relative temporal and spatial patterns in nitrate availability in normal salinity areas of the world ocean. After an analysis of local NDT variability at four time series stations demonstrated temporal stability compared to SST, [SST–NDT] as a Nitrate Availability Index (NAI) was calculated for April (boreal spring or austral fall) and October (boreal fall and austral spring) for the whole ERSSTv1 data set and for selected years of the ERSSTv2 data set using the global NDT climatology. The more negative the NAI difference, the greater the expected surface nitrate. The more positive the NAI difference, the greater the intensity of temperature stratification between the surface and the nitracline and thus the less likely that nitrate mixed to the surface. The records from April and October both showed that decreased nitrate availability, defined by both smaller negative NAI differences and larger positive NAI differences, generally though not universally occurred throughout the 20th century in association with global warming. The greatest decreases in nitrate availability occurred in two warming events in the time periods 1909–1937 and 1977–present in the Northern Hemisphere and 1926–1937 and 1950–1990 in the Southern Hemisphere. Different areas of the world ocean were affected in each warming event. Prominent exceptions in the ERSSTv1 analysis where 20th century nitrate availability actually increased in at least one season were in western parts of the South Indian, the North Pacific, the equatorial Pacific, the South Pacific, the North Atlantic, and the South Atlantic and in eastern parts of the South Pacific and South Atlantic. The ERSSTv2 analysis also showed increased 20th century nitrate availability in the eastern subarctic Pacific. The nitrate availability trends resulting from the present analysis agree with various literature reports on regional changes in plant nutrient availability, on increased occurrences of harmful algal blooms often associated with dinoflagellates that are better able to access subsurface nitrate pools, and on decadal changes in marine fisheries. They also raise concerns about the resilience of historical patterns of pelagic community structure and function in response to a warming trend continuing into the 21st century. [Copyright &y& Elsevier]