Monitoring the flow of Atlantic water through the Faroe-Shetland Channel

This report presents results from an experiment, carried out in 2011-2012 within the EU-THOR project to investigate whether future monitoring of the Atlantic water transport through the Faroe-Shetland Channel might be more efficiently achieved on another section than the traditional Munken-Fair Isle section. The new section is less affected by meso-scale activity and narrower, allowing better horizontal resolution of the mooring array, but the experiment revealed that moving to the new section involved other drawbacks. The experiment also confirmed an earlier conjecture that data from satellite altimetry might provide better estimates of transport variations than estimates based on in situ measurements, solely. Previous efforts to determine the average volume transport of Atlantic water through the channel and its variations have been hampered by lack of information on the thickness variations of the Atlantic layer. Re-evaluating the historical data set, we find that the transport estimates are not significantly affected by assuming that the lower boundary of the Atlantic layer is fixed, equal to the average 5°C-isotherm. Based on the conclusions of this report, we recommend that future in situ monitoring in the channel is re-focused

The distribution of blue whiting west of the British Isles and Ireland

Northern blue whiting is a small abundant pelagic gadoid that is widely distributed in the northeast Atlantic and one of the most commercially valuable species west of the British Isles and Ireland. Over the last two decades the northeast Atlantic stock has undergone dramatic changes in abundance. The stock size decreased dramatically from 2007 to 2011, but has since shown signs of recovery. Changes in recruitment levels have occurred almost simultaneously with unusual changes in the north Atlantic ecosystem and oceanography. These links may suggest a causal linkage and the possibility of improving our understanding of the recruitment and spawning stock distribution. Here we use a set of geostatistical indices to describe the temporal and spatial patterns of the northeast Atlantic blue whiting stock in spring of 2006-2014. Geostatistical indices were computed to investigate changes in the spatial distribution, dynamics and variability of the stock in terms of density and location. Indices revealed 3 different distribution patterns over the time series. Main concentrations were either found around Rockall (first years), west of the Hebrides (2008-2013) or in the southern survey area (2014). The distribution was found to be age structured, with young blue whiting mainly concentrated in shallower areas (1000 m). A general additive mixed model (GAMM) was used to model the distribution of blue whiting according to environmental conditions and location.</p