Seasonal and inter-annual variability in nutrient supply in relation to mixing in the Bay of Biscay

Post-print

Overview of Bering/Chukchi Sea Wave States for Selected Severe Storms

Strong storms are regular features over the ocean west of Alaska. These systems often loiter, generating moderate to severe marine states which can exhibit persistence, maximizing damage and hazard potential. This analysis presents the wave states associated with selected storms over the Bering and Chukchi Seas. These include the damaging events of October 2004, September 2005, and November 2009, along with a strong event from September 2011 that exhibited north winds. For each event a brief synoptic overview is presented followed by consideration of the resultant wave state, including parameters such as wave steepness. Wave data come from NOAA’s WAVEWATCH III operational global ocean wave model, implemented locally on the Arctic Region Supercomputing Center at University of Alaska Fairbanks. Comparison with observational data gathered by a wave buoy, funded by the US Environmental Protection Agency/NOAA and deployed in 2011, is also undertaken.NOAA Grant NA08OAR4600856, “Social Vulnerability to Climate Change in the Alaskan Coastal Zone

Observations of vertical mixing in autumn and its effect on the autumn phytoplankton bloom

This work examines the seasonal cycle of density structure and its influence on primary production in a temperate shelf sea, with a particular focus on the breakdown of stratification in autumn. We do this by combining new, high resolution observations of water column structure, meteorological forcing, nitrate and chlorophyll fluorescence collected between March 2014 and July 2015 on the North West European Shelf. Our results challenge the generally accepted assumption that convection dominates over wind driven mixing resulting in seasonal breakdown of stratification. Furthermore we found, that vertical mixing in autumn not only transformed the vertical density structure but also the vertical structure of chlorophyll biomass and surface nutrients. The subsurface chlorophyll maximum was eroded and a vertically homogeneous profile of chlorophyll biomass established itself above the pycnocline. This increased mixing also led to replenishment of surface nitrate concentrations, which supported an autumn phytoplankton bloom. While the significance of phytoplankton blooms in autumn has previously not been well quantified, we argue that these can act as a significant contributor to the seasonal drawdown of carbon

Predicting the exposure of diving grey seals to shipping noise.

There is high spatial overlap between grey seals and shipping traffic, and the functional hearing range of grey seals indicates sensitivity to underwater noise emitted by ships. However, there is still very little data regarding the exposure of grey seals to shipping noise, constraining effective policy decisions. Particularly, there are few predictions that consider the at-sea movement of seals. Consequently, this study aimed to predict the exposure of adult grey seals and pups to shipping noise along a three-dimensional movement track, and assess the influence of shipping characteristics on sound exposure levels. Using ship location data, a ship source model, and the acoustic propagation model, RAMSurf, this study estimated weighted 24-h sound exposure levels (10-1000 Hz) (SELw). Median predicted 24-h SELw was 128 and 142 dB re 1 μPa2s for the pups and adults, respectively. The predicted exposure of seals to shipping noise did not exceed best evidence thresholds for temporary threshold shift. Exposure was mediated by the number of ships, ship source level, the distance between seals and ships, and the at-sea behaviour of the seals. The results can inform regulatory planning related to anthropogenic pressures on seal populations