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Liverpool, United Kingdom

Marsh R.,UK National Oceanography Center | Hickman A.E.,UK National Oceanography Center | Sharples J.,University of Liverpool | Sharples J.,National Oceanography Center Liverpool
Geoscientific Model Development | Year: 2015

An established one-dimensional (1-D) model of Shelf Sea Physics and Primary Production (S2P3) is adapted for flexible use in selected regional settings over selected periods of time. This Regional adaptation of S2P3, the S2P3-R framework (v1.0), can be efficiently used to investigate physical and biological phenomena in shelf seas that are strongly controlled by vertical processes. These include spring blooms that follow the onset of stratification, tidal mixing fronts that seasonally develop at boundaries between mixed and stratified water, and sub-surface chlorophyll maxima that persist throughout summer. While not representing 3-D processes, S2P3-R reveals the horizontal variation of the key 1-D (vertical) processes. S2P3-R should therefore only be used in regions where horizontal processes-including mean flows, eddy fluxes and internal tides-are known to exert a weak influence in comparison with vertical processes. In such cases, S2P3-R may be used as a highly versatile research tool, alongside more complex and computationally expensive models. In undergraduate oceanography modules and research projects, the model serves as an effective practical tool for linking theory and field observations. Three different regional configurations of S2P3-R are described, illustrating a range of diagnostics, evaluated where practical with observations. The model can be forced with daily meteorological variables for any selected year in the reanalysis era (1948 onwards). Example simulations illustrate the considerable extent of synoptic-to-interannual variability in the physics and biology of shelf seas. In discussion, the present limitations of S2P3-R are emphasised, and future developments are outlined. © 2015 Author(s).

Williams S.D.P.,National Oceanography Center Liverpool | Moore P.,Northumbria University | King M.A.,Northumbria University | King M.A.,University of Tasmania | Whitehouse P.L.,Durham University
Earth and Planetary Science Letters | Year: 2014

Previous GRACE-derived ice mass trends and accelerations have almost entirely been based on an assumption that the residuals to a regression model (including also semi-annual, annual and tidal aliasing terms) are not serially correlated. We consider ice mass change time series for Antarctica and show that significant autocorrelation is, in fact, present. We examine power-law and autoregressive models and compare them to those that assume white (uncorrelated) noise. The data do not let us separate autoregressive and power-law models but both indicate that white noise uncertainties need to be scaled up by a factor of up to 4 for accelerations and 6 for linear rates, depending on length of observations and location. For the whole of Antarctica, East Antarctica and West Antarctica the scale factors are 1.5, 1.5 and 2.2 respectively for the trends and, for the accelerations, 1.5, 1.5 and 2.1. Substantially lower scale-factors are required for offshore time series, suggesting much of the time-correlation is related to continental mass changes. Despite the higher uncertainties, we find significant (2-sigma) accelerations over much of West Antarctica (overall increasing mass loss) and Dronning Maud Land (increasing mass gain) as well as a marginally significant acceleration for the ice sheet as a whole (increasing mass loss). © 2013 The Authors.

Shapiro G.,University of Plymouth | Luneva M.,National Oceanography Center Liverpool | Pickering J.,University of Plymouth | Storkey D.,UK Met Office
Ocean Science | Year: 2013

Results of a sensitivity study are presented from various configurations of the NEMO ocean model in the Black Sea. The standard choices of vertical discretization, viz. iz/i levels, is/i coordinates and enveloped is/i coordinates, all show their limitations in the areas of complex topography. Two new hybrid vertical coordinate schemes are presented: the "s-on-top-of- z" and its enveloped version. The hybrid grids use is/i coordinates or enveloped is/i coordinates in the upper layer, from the sea surface to the depth of the shelf break, and z-coordinates are set below this level. The study is carried out for a number of idealised and real world settings. The hybrid schemes help reduce errors generated by the standard schemes in the areas of steep topography. Results of sensitivity tests with various horizontal diffusion formulations are used to identify the optimum value of Smagorinsky diffusivity coefficient to best represent the mesoscale activity. © Author(s) 2013.

Panton A.,University of Liverpool | Mahaffey C.,University of Liverpool | Greenwood N.,CEFAS - Center for Environment, Fisheries and Aquaculture Science | Hopkins J.,National Oceanography Center Liverpool | And 2 more authors.
Ocean Dynamics | Year: 2012

Regions of freshwater influence (ROFIs) are dynamic areas within the coastal seas that experience cycles of stability driven by density gradients and the spring-neap tidal cycle. As a result, pulses of biological production may occur on a more frequent timescale than the classic seasonal cycle. Net community production (NCP) rates and chlorophyll a concentration are presented from a site within the ROFI of Liverpool Bay and compared to similar measurements made at a site outside the ROFI during 2009. The influence of water column stability on biological production in the ROFI was also investigated using high-frequency observations from a Cefas Smartbuoy. Both sites were autotrophic from spring to autumn before becoming heterotrophic over winter. NCP at the inshore site was estimated to range from 30.8 to 50.4 gC m -2 year -1. A linear relationship detected between chlorophyll a and NCP from both sites was used to estimate metabolic balance over 1 year at the ROFI site using high-resolution chlorophyll a concentrations from the Smartbuoy but was found to poorly replicate NCP rates compared to those derived from dissolved oxygen fluxes. There was no clear biological response to periods of stratification within the ROFI, and it is proposed that changes in light attenuation in the Liverpool Bay ROFI, driven not only by stratification but also by fluctuations in riverine sediment load, most likely play an important role in controlling phytoplankton growth in this region. © 2011 Springer Science+Business Media, LLC.

Rickards L.,British Oceanographic Data Center | Brown J.,British Oceanographic Data Center | Hibbert A.,National Oceanography Center Liverpool | Woodworth P.,Permanent Service for Mean Sea Level | And 2 more authors.
Journal of Coastal Conservation | Year: 2013

In this Comment we refer to our strong reservations concerning the paper by Powell et al. J Coast Conserv, (2012) recently published on the Online First web site of the Journal of Coastal Conservation. The paper makes a number of comments on data obtained from the Permanent Service for Mean Sea Level (PSMSL) and British Oceanographic Data Centre (BODC) which are incorrect or misleading. In addition, some of their comments on sea-level science in general need to be challenged and corrected. © 2013 Springer Science+Business Media Dordrecht.

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