Holocene temporal and spatial variation in the radiocarbon reservoir age of three Danish fjords

Holocene temporal and spatial reservoir age variations have been investigated in three Danish fjords (Horsens Fjord, Tempelkrog in Isefjord and Skælskør Nor) by ¹⁴C dating paired samples of terrestrial plant material and marine molluscs in sediment cores. The local reservoir age offsets at all three sites show significant temporal and local variations, with ΔR(t) values ranging from −425 to 620 yr. The ΔR(t) values for Horsens Fjord range from −425 to 0 yr, for Tempelkrog from −230 to 360 yr and for Skælskør Nor from 30 to 620 yr. The differences are best explained by differences in local hydrographic configuration, catchment characteristics and connection with the inner Danish seas. The observed temporal ΔR(t) variations are not synchronous, which is probably due to the overriding role played by numerous local factors affecting the ΔR(t) values. Based on the reservoir data from Horsens Fjord and Tempelkrog, it is suggested as a working hypothesis that the ΔR value for Kattegat prior to 4500 cal. yr BP was negative, i.e. between −130 and −200 yr. The temporal and local variations in the reservoir age underline the problems and uncertainties connected with radiocarbon-dating fossil human skeletons with marine diets. Overall, our data show that reservoir ages in Danish fjords and estuaries are both site-specific and time-specific, implying that modern reservoir ages cannot simply be applied back in time. This conclusion may also be valid in the case of fjords and estuaries in large parts of the Baltic too.     

On measuring time-averaged velocities in open channel flow

The problem of finding the necessary measuring time to determine the mean velocity in open channel flow is treated. The result shows an ‘on the safe side’ relation between measuring time and standard deviation of measured velocities.     

Climate change impacts on Namibia's natural resources and economy

Climate change is likely to exacerbate the dry conditions already experienced in southern Africa. When rainfall does come, it is likely to be in bursts of greater intensity, leading to erosion and flood damage. However, these predictions have had very little influence on policy in southern African countries. Computable general equilibrium (CGE) model simulations for Namibia indicate that over 20 years, annual losses to the Namibian economy could be up to 5% of GDP, due to the impact that climate change will have on its natural resources alone. This will affect the poorest people the most, with resulting constraints on employment opportunities and declining wages, especially for unskilled labour in rural areas. Namibia must take steps to ensure that all its policies and activities are ‘climate proofed’ and that it has a strategy to deal with displaced farmers and farm workers. The need to mainstream climate change into policies and planning is clear, and it is the responsibility of industrialized nations, who have largely created the problem of climate change, to help Namibia and other vulnerable countries cope with climate change impacts and plan for a climate-constrained future.     

Impact of the Arctic Fox Alopex lagopus on nesting success of geese in southeast Svalbard, 1989

Goose populations, with special emphasis on Light-bellied Brent Geese Branta bernicla hrota , were censured in Tusenøyane and Tjuvfjorden, southeast Svalbard, July-August 1989. A total of 425 non-breeding Brent Geese, 210 Barnacle Geese Branta leucopsis and 421 Pink-footed Geese Anser bra-chyrhynchus and 11, 2 and 3 families of the three species, respectively, were counted. Brent Geese attempted to nest on 6 of the 20 islands surveyed, and were successful on four. Barnacle Geese attempted to nest on three islands and were successful on two. Many islands known to be traditional nesting sites were entirely void of geese. Pink-footed Geese were only seen in Tjuvfjorden. The breeding failure on the islands was linked to the presence of the Arctic Fox Alopex lagopus which probably caused the geese to completely give up the attempt to nest. On one island the fox had apparently arrived after nest initiation and ravaged 45 Brent Goose and Barnacle Goose nests. It is likely that the foxes stranded on the islands during ice break-up. As a consequence of the presence of foxes on most of Tusenøyane, more than half of the potential breeding segment of the Svalbard Brent Goose population failed to nest in the summer of 1989.