Climate variability and physical forcing of the food webs and the carbon budget on panarctic shelves

Brief overviews of the Arctic’s atmosphere, ice cover, circulation, primary production and sediment regime are given to provide a conceptual framework for considering panarctic shelves under scenarios of climate variability. We draw on past ‘regional’ studies to scale-up to the panarctic perspective. Within each discipline a synthesis of salient distributions and processes is given, and then functions are noted that are critically poised and/or near transition and thereby sensitive to climate variability and change. The various shelf regions are described and distinguished among three types: inflow shelves, interior shelves and outflow shelves. Emphasis is on projected climate changes that will likely have the greatest impact on shelf-basin exchange, productivity and sediment processes including (a) changes in wind fields (e.g. currents, ice drift, upwelling and downwelling); (b) changes in sea ice distribution (e.g. radiation and wind regimes, enhanced upwelling and mixing, ice transport and scour resuspension, primary production); and (c) changes in hydrology (e.g. sediment and organic carbon delivery, nutrient supplies). A discussion is given of the key rate-controlling processes, which differ for different properties and shelf types, as do the likely responses; that is, the distributions of nutrients, organic carbon, freshwater, sediments, and trace minerals will all respond differently to climate forcing.A fundamental conclusion is that the changes associated with light, nutrients, productivity and ice cover likely will be greatest at the shelf-break and margins, and that this forms a natural focus for a coordinated international effort. Recognizing that the real value of climate research is to prepare society for possible futures, and that such research must be based both on an understanding of the past (e.g. the palaeo-record) as well as an ability to reliably predict future scenarios (e.g. validated models), two recommendations emerge: firstly, a comprehensive survey of circumpolar shelf-break and slope sediments would provide long-term synchronous records of shelf-interior ocean exchange and primary production at the shelf edge; secondly, a synoptic panarctic ice and ocean survey using heavy icebreakers, aircraft, moorings and satellites would provide the validation data and knowledge required to properly model key forcing processes at the margins.     

Postglacial relative sea‐level rise in the Limfjord region,northern Jutland,Denmark

A new core drilled at Nørrekær Enge, Løgstør, Denmark, shows terrestrial lake and bog sediments lying beneath 10 m of marine sediments. Pollen analysis, ¹⁴C dating and sedimentary observations show that these sediments relate to an ancient lake basin that was flooded when the rising sea levels reached 8.0 m b.s.l. This new study has allowed a review of previous data relating to shoreline displacement from the Limfjord region of northern Jutland, Denmark. Here we present a new shoreline displacement curve spanning the period between c. 11 700 and 7700 cal. a BP and built upon the Nørrekær Enge data and data from seven other boreholes and excavations from the Limfjord region. A previous shoreline displacement curve for this region suggested a very rapid relative sea‐level rise of 3 to 5 m 100 a^?1 whereas this new curve suggests a much slower rise of around 1 m 100 a^?1, similar to global rates.     

Magnetic and viscous coupling at the core–mantle boundary: inferences from observations of the Earth's nutations

Dissipative core–mantle coupling is evident in observations of the Earth's nutations, although the source of this coupling is uncertain. Magnetic coupling occurs when conducting materials on either side of the boundary move through a magnetic field. In order to explain the nutation observations with magnetic coupling, we must assume a high (metallic) conductivity on the mantle side of the boundary and a rms radial field of 0.69 mT. Much of this field occurs at short wavelengths, which cannot be observed directly at the surface. High levels of short-wavelength field impose demands on the power needed to regenerate the field through dynamo action in the core. We use a numerical dynamo model from the study of Christensen & Aubert (2006) to assess whether the required short-wavelength field is physically plausible. By scaling the numerical solution to a model with sufficient short-wavelength field, we obtain a total ohmic dissipation of 0.7–1 TW, which is within current uncertainties. Viscous coupling is another possible explanation for the nutation observations, although the effective viscosity required for this is 0.03 m² s⁻¹ or higher. Such high viscosities are commonly interpreted as an eddy viscosity. However, physical considerations and laboratory experiments limit the eddy viscosity to 10⁻⁴ m² s⁻¹, which suggests that viscous coupling can only explain a few percent of the dissipative torque between the core and the mantle.     

Importance of Air-Sea Coupling in Simulating Tropical Cyclone Intensity at Landfall

An atmosphere-only model system for making seasonal prediction and projecting future intensities of landfalling tropical cyclones (TCs) along the South China coast is upgraded by including ocean and wave models. A total of 642 TCs have been re-simulated using the new system to produce a climatology of TC intensity in the South China Sea. Detailed comparisons of the simulations from the atmosphere-only and the fully coupled systems reveal that the inclusion of the additional ocean and wave models enable differential sea surface temperature responses to various TC characteristics such as translational speed and size. In particular, interaction with the ocean does not necessarily imply a weakening of the TC, with the coastal bathymetry possibly playing a role in causing a near-shore intensification of the TC. These results suggest that to simulate the evolution of TC structure more accurately, it is essential to use an air-sea coupled model instead of an atmosphere-only model.     

Quadratic covariance estimation and equivalence of predictions

This article illustrates the use of linear and nonlinear regression models to obtain quadratic estimates of covariance parameters. These models lead to new insights into the motivation behind estimation methods, the relationships between different methods, and the relationship of covariance estimation to prediction. In particular, we derive the standard estimating equations for minimum norm quadratic unbiased translation invariant estimates (MINQUEs) from an appropriate linear model. Connections between the linear model, minimum variance quadratic unbiased translation invariant estimates (MIVQUEs), and MINQUEs are examined and we provide a minimum norm justification for the use of one-step normal theory maximum likelihood estimates. A nonlinear regression model is used to define MINQUEs for nonlinear covariance structures and obtain REML estimates. Finally, the equivalence of predictions under various models is examined when covariance parameters are estimated. In particular, we establish that when using MINQUE, iterative MINQUE, or restricted maximum likelihood (REML) estimates, the choice between a stationary covariance function and an intrinsically stationary semivariogram is irrelevant to predictions and estimated prediction variances.     

New multifunctional hunting landscapes in Denmark

Between 1992 and 2008 subsidization of mandatory set aside land under the EU Common Agricultural Policy (CAP) gave rise to the establishment of a characteristic type of multifunctional hunting landscapes in Denmark, primarily located on fallow land in tilled valley bottoms. A national survey of these landscapes in 2006 has been carried out and 1061 hunting areas have been identified nationwide. Subsidies relating to set aside land acted as a supplementary type of income, which supported the development of multifunctional land use on marginal soils where the income from hunting and subsidies in combination was a viable alternative to monofunctional rotational agriculture. Hunting landscapes developed as the consequence of landscape management strategies designed to comply with the requirements of the CAP while improving habitat conditions for wildlife and increasing income from hunting rental activities. Forty-seven percent of the hunting landscapes in 2006 were in rotational production in 2010 while 19% were used for other agricultural purposes and 34% were taken out of the subsidy regime and removed from the general agricultural register. In 2012, a total of 431 such areas ? 41% of the areas identified in 2006 ? were still used for hunting. The number and geographical distribution of the hunting landscapes seems closely related to the potential average hunting rent, the level of urbanisation and the occurrence of manorial estates with traditions for multifunctional land use as part of their economic strategy. Implications for the ongoing discussion on land use policy concerning land sharing vs. land sparing is discussed.