Nonlinear Shallow Water Theories for Coastal Waves

Ocean waves entering the near-shore zone undergo nonlinear and dispersive processes. This paper reviews nonlinear models, focusing on the so-called Serre equations. Techniques to overcome their limitations with respect to the phase speed are presented. Nonlinear behaviours are compared with theoretical results concerning the properties of Stokes waves. In addition, the models are tested against experiments concerning periodic wave transformation over a bar topography and of the shoaling of solitary waves on a beach.     

Growing season evapotranspiration in boreal fens in the Athabasca Oil Sands Region: Variability and environmental controls

Current efforts to assess changes to the wetland hydrology caused by growing anthropogenic pressures in the Athabasca Oil Sands Region (AOSR) require well-founded spatial and temporal estimates of actual evapotranspiration (ET), which is the dominant component of the water budget in this region. This study assessed growing season (May–September) and peak growing season (July) ET variability at a treed moderate-rich fen and treed poor fen (in 2013–2018), open poor fen (in 2011–2014), and saline fen (in 2015–2018) using eddy covariance technique and a set of complementary environmental data. Seasonal fluctuations in ET were positively related to net radiation, air temperature and vapour pressure deficit and followed trends typical for the Boreal Plains (BP) and AOSR with highest rates in June–July. However, no strong effect of water table position on ET was found. Strong surface control on ET is evident from lower ET values than potential evapotranspiration (PET); the lowest ET/PET was observed at saline fen, followed by open fen, moderately treed fen, and heavily treed fen, suggesting a strong influence of vegetation on water loss. In most years PET exceeded precipitation (P), and positive relations between P/PET and ET were observed with the highest July ET rates occurring under P/PET ~1. However, during months with P/PET > 1, increased P/PET was associated with decreased July ET. With respect to 30-year mean values of air temperature and P in the area, both dry and wet, cool and warm growing seasons (GS) were observed. No clear trends between ET values and GS wetness/coldness were found, but all wet GS were characterized by peak growing seasons with high daily ET variability.     

Evaluating vegetative transplant success in Posidonia australis: a field trial with habitat enhancement

Seagrasses in Western Australia grow on open coastlines that are wave and surge exposed, which are known to reduce transplant success. This study investigated the use of habitat enhancement procedures to improve the survival and expansion of Posidonia australis transplants. Limited success transplanting P. australis vegetative propagules (plugs) was achieved after habitat enhancement was implemented, using artificial seagrass (ASG) mats to emulate a "surrogate" seagrass meadow. The ASG mats enhanced one aspect of the habitat (stabilised sediment grain size) but did not suitably stabilise erosion and accretion. Transplant survival was significantly increased (up to 50% survival) in 60% of the sites where ASG mats were present. However, only 8% of the total transplant population exhibited rhizome extension (3.2+/-0.11 mmd(-1)).     

Scientific challenges and instrumentation for the International Meridian Circle Program

Earth's ecosystems and human activities are threatened by a broad spectrum of hazards of major importance for the safety of ground infrastructures,space systems...     

Quick matching technique to study the relationship between solar radius and luminosity variations

A simple matching technique is developed which allows us to compute the response of the solar envelope to perturbations which occur within the solar convective region, and in timescales of importance to climate. This technique is applied to perturbation of the convective efficiency (-mechanism), and of the non-gas component of the pressure in different regions of the convection zone (-mechanism). The results indicate that while either perturbation affects the solar luminosity, the -mechanism has almost no effect on the solar outer radius, regardless of the affected region, whereas the -mechanism produces radius changes which may be large if the location of perturbation is deep enough.