Improved Simulation of the Polar Atmospheric Boundary Layer by Accounting for Aerodynamic Roughness in the Parameterization of Surface Scalar Exchange Over Sea Ice

A new, simple parameterization scheme for scalar (heat and moisture) exchange over sea ice and the marginal ice zone is tested in a numerical weather and climate prediction model. This new “Blended A87” scheme accounts for the influence of aerodynamic roughness on the relationship between momentum and scalar exchange over consolidated sea ice, in line with long-standing theory and recent field observations, and in contrast to the crude schemes currently operational in most models. Using aircraft observations and Met Office Unified Model simulations of cold-air outbreak (CAO) conditions over aerodynamically rough sea ice, we demonstrate striking improvements in model performance when the Blended A87 scheme replaces the model's operational treatment for surface scalar exchange, provided that the aerodynamic roughness over consolidated ice is appropriately prescribed. The mean biases in surface sensible heat flux, surface latent heat flux, near-surface air temperature, and surface temperature reduce from 25 to 11 W m⁻², 22 to 12 W m⁻², 0.8 to 0.0 K, and 1.4 to 0.8 K, respectively. We demonstrate that such impacts on surface exchange over sea ice can have a marked impact on the evolution of the atmospheric boundary layer across hundreds of kilometres downwind of the sea ice during CAO conditions in the model. Our results highlight the importance of spatiotemporal variability in the topography of consolidated sea ice for both momentum and scalar exchange over sea ice; accounting for which remains a key challenge for modeling polar weather and climate

Surface Heat and Moisture Exchange in the Marginal Ice Zone: Observations and a New Parameterization Scheme for Weather and Climate Models

Aircraft observations from two Arctic field campaigns are used to characterize and model surface heat and moisture exchange over the marginal ice zone (MIZ). We show that the surface roughness lengths for heat and moisture over uninterrupted sea ice vary with roughness Reynolds number (R; itself a function of the roughness length for momentum, 0z, and surface wind stress), with a peak at the transition between aerodynamically smooth (R2.5) regimes. A pre-existing theoretical model based on surface-renewal theory accurately reproduces this peak, in contrast to the simple parameterizations currently employed in two state-of-the-art numerical weather prediction models, which are insensitive to R. We propose a new, simple parameterization for surface exchange over the MIZ that blends this theoretical model for sea ice with surface exchange over water as a function of sea ice concentration. In offline tests, this new scheme performs much better than the existing schemes for the rough conditions observed during the ‘Iceland Greenland Seas Project’ field campaign. The bias in total turbulent heat flux across the MIZ is reduced to only 13W m2 for the new scheme, from 48 and 80W m2 for the Met Office Unified Model and ECMWF Integrated Forecast System schemes, respectively. It also performs marginally better for the comparatively smooth conditions observed during the ‘Aerosol-Cloud Coupling and Climate Interactions in the Arctic’ field campaign. The new surface exchange scheme has the benefit of being physically-motivated, comparatively accurate and straightforward to implement, although to reap the full benefits an improvement to the representation of sea ice topography via 0zis require

Does coastal light pollution alter the nocturnal behavior and blood physiology of juvenile bonefsh (Albula vulpes)?

Light pollution is a prevalent, but often overlooked, ecological concern in a variety of ecosystems. Marine environments are subjected to artifcial lighting from coastal development, in addition to ofshore sources, such as fshing vessels, oil platforms and cruise ships. Fish species that rely on nearshore habitats are most signifcantly impacted by coastal light pollution, as they are often limited to nearshore habitats due to predation risk in deeper ofshore waters, particularly as juveniles. Juvenile bonefsh [Albula vulpes (Linnaeus, 1758)] inhabit the nearshore environment, and are therefore exposed to coastal lighting and other watershed development impacts. Here, we assessed juvenile bonefsh behavior and physiology in the presence of two common light sources: constant street lighting (high pressure sodium) and intermittent car headlights (H4 halogen). Te behavioral responses were compared with a night and day control, whereas physiology was compared only with a night control. Each behavioral trial had two time periods: light and recovery (2 hrs each). Physiology (blood glucose and whole body cortisol) was assessed after an overnight 8-hr exposure. Te results suggest that there is no effect of light pollution on the swimming behavior or whole body cortisol of juvenile bonefsh, but that both forms of light pollution resulted in elevated blood glucose concentrations (a simple stress indicator) relative to controls, with constant light glucose levels being signifcantly higher. Further research is needed to understand the ecological consequences of light pollution on bonefsh and other coastal marine fsh using additional endpoints, assessing fsh over longer time periods, and ideally combining data from the laboratory and the feld