The Fate of Greenland— Lessons from Abrupt Climate Change

In times of chronic lack of resources for academic research and ever increasing competition for grants it was every scientists dream coming true: a billionaire patron comes along and hands you unlimited resources to pursue the research that lies closest to your heart. In this case, the late Gary Comer (1927–2006), who had in 2001 taken his yacht through the notorious Northwest Passage then free of sea ice, engaged a team of outstanding climate scientists to lead a search for causal links controlling abrupt global climate change: Wallace (Wally) S. Broecker of Columbia University, George H. Denton of the University of Maine, and Richard B. Allen of Pennsylvania State University. Broecker is an oceanographer/geochemist, who is probably best known for developing the idea of a global “conveyor belt” linking the circulation of the global oceans and controlling large scale climate oscillations in the past; Denton is a geologist, long concerned with the (bi-polar) geological history of the large Quaternary ice sheets; and Alley is a glaciologist who is perhaps best known for his contributions on the relationships between Earth\u27s cryosphere and global climate change. All three have developed ideas and concepts on rapid ocean-atmosphere-cryosphere reorganizations over past glacial cycles. Philip Conkling, a prominent Maine naturalist who participated in many of Comer’s expeditions, played a vital role in putting the team together

Late Weichselian Glacial Geology of the Lower Borgarfjördur Region, Western Iceland: a Preliminary Report

Morphological and lithostratigraphical investigations have revealed two successive glacial advances of Late Weichselian age in the lower Borgarfjördur region, Western Iceland. Studies of the Melabakkar-Ásbakkar coastal cliffs have disclosed a complex of glaciomarine sediments and tills, accompanied by glaciofluvial deposits from ice marginal sources. A brief description is given for each of the major lithostratigraphical units, and a depositional model for the sequence is outlined. The first glacial advance occurred some time shortly after 12 000 radiocarbon years before present (BP), and the second one around 11 000 BP. By 10 000 BP the glaciers had retreated from the lowlands and the sea transgressed to 60 m above present sea level, where extensive marine terraces were formed.Key words: Borgarfjördur, western Iceland, Melabakkar-ásbakkar, glacial geology, glacia chronology, Late WeichselianMots clés: Borgarfjördur, ouest de l'Icelande, Melabakkar-ásbakkar, géologie glaciale, chronologie glaciaire, Weichsel supérieu

Shorter trawls improve size selection of northern shrimp

Discards of small northern shrimp (Pandalus borealis) are a problem in the Skagerrak northern shrimp trawl fishery. To reduce catches of small shrimp, we studied the effect of trawl belly length on size selectivity in November 2017 and June 2018 onboard 15 and 27 m double-rigged shrimp trawlers. The selectivity of the vessels’ standard trawl was compared with a trawl differing only in the belly length, being 37% shorter. The trawls had 40 mm bottom panels and cod ends of 35 mm mesh sizes. Eleven and 14 hauls were made, respectively, in 2017 aboard the 15 m vessel and in 2018 aboard the 27 m vessel. The trawls fished shrimp above 19 mm carapace length equally, while catch rates of shrimp below 15.5–16 mm carapace length in the shorter trawl were more than halved. The results were consistent between the two vessels. In short, modifying trawl length is a simple design modification that can reduce catches of small shrimp. Bycatch of Norway pout (Trisopterus esmarkii) was slightly reduced in the shorter trawl, unrelated to fish length.acceptedVersio

Selective flatfish seine: A knee-high demersal seine barely catches cod

Norwegian coastal cod (Gadus morhua) protection restricts the use of active fishing gears. Demersal seines, acknowledged as being efficient for targeting flatfish, are therefore largely excluded from the fjords. To exploit plaice (Pleuronectes platessa), a species-selective gear that avoids catching cod is needed. We therefore designed a low-rise demersal seine with a 0.6 m vertical opening and tested it on fishing grounds in Lofoten (Northern Norway), comparing it with a conventional seine that had a vertical opening of ∼3.5 m, and fished both during the day and at night. Six to nine hauls were taken with each of the four gear/time-of-day categories (32 hauls in total). The low-rise seine caught no fewer plaice during day-time fishing, but less at night. Cod and haddock (Melanogrammus aeglefinus) catches were reduced by 94% and 98%, respectively, while catches of sole (Solea solea) increased with the low-rise seine. No catch differences were found for halibut (Hippoglossus hippoglossus), common dab (Limanda limanda), or monkfish (Lophius piscatorius). The low-rise seine therefore enables targeting flatfish while avoiding gadoid catches, although loss of plaice during night-time fishing is to be expected.publishedVersio

Surface selection of haddock and cod in the Norwegian demersal seine fisheries

Size selection in active fishing gears is a continuous process and undersized fish may escape during the whole fishing operation. Fish that escape during the surface hauling operation are likely to experience higher mortality due to barotrauma-related stress than fish escaping at the fishing depth during the towing process. A well-functioning selectivity device should therefore select mostly at depth for enhancing survival probabilities of escaping fish. The current gear regulation in the Norwegian demersal seine fishery is likely to cause large proportion of undersized fish to escape at the surface. In this study, we estimated surface selection of haddock and cod in demersal seine by using an automatic release system and a small meshed codend that collected fish escaping during surface hauling. The collecting bag contained 19% undersized haddock compared to 10% in the conventional square-mesh codend indicating that about 50% of undersized haddock brought to the surface were released. The proportions of undersized cod were 8% for the collecting bag and 1% for the conventional square-mesh codend. These results demonstrate that surface selection is significant for both haddock and cod. Based on this finding, we discuss methods to improve size selectivity at the fishing depth.publishedVersio

Development and evaluation of dynamic catch control devices in the demersal seine fisheries for cod (Gadus morhua)

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The dynamic Arctic

Research campaigns over the last decade have yielded a growing stream of data that highlight the dynamic nature of Arctic cryosphere and climate change over a range of time scales. As a consequence, rather than seeing the Arctic as a near static environment in which large scale changes occur slowly, we now view the Arctic as a system that is typified by frequent, large and abrupt changes. The traditional focus on end members in the system - glacial versus interglacial periods - has been replaced by a new interest in understanding the patterns and causes of such dynamic change. Instead of interpreting changes almost exclusively as near linear responses to external forcing (e.g. orbitally-forced climate change), research is now concentrated on the importance of strong feedback mechanisms that in our palaeo-archives often border on chaotic behaviour. The last decade of research has revealed the importance of on-off switching of ice streams, strong feedbacks between sea level and ice sheets, spatial and temporal changes in ice shelves and perennial sea ice, as well as alterations in ice sheet dynamics caused by shifting centres of mass in multi-dome ice sheets. Recent advances in dating techniques and modelling have improved our understanding of leads and lags that exist in different Arctic systems, on their interactions and the driving mechanisms of change. Future Arctic research challenges include further emphases on rapid transitions and untangling the feedback mechanisms as well as the time scales they operate on

Artificial light improves size selection for northern shrimp (Pandalus borealis) in trawls

Size selection in the northern shrimp (Pandalus borealis) trawl fisheries is a widely studied topic. While the focus has largely been on codend and grid selectivity, studies have shown the importance of other design changes and the application of artificial light to evoke behavioural responses. LED lights of three different colours; green (~470–580 nm), white (~425–750 nm) and red (~580–670 nm), were mounted in the belly section of a shrimp trawl to investigate their influence on the overall selectivity of the trawl. The study was conducted using a twin-trawl setup, one with light and the other without light. For catch-comparison analysis, a polynomial regression with random effects was applied. The number of valid hauls with green, white and red lights were eleven, eight, and nine, respectively. All lights tested significantly affected the length-dependent retention of shrimp. Green light had the greatest effect, red the least. Significant loss was observed for shrimp below 17.5 mm carapace length (CL) for green light, 19.5 mm CL for white and 20.8 mm CL for red light.acceptedVersio