Highly precise and reproducible radiocarbon (14C) measurements are regularly performed at the Heidelberg Institute for Environmental Physics, Heidelberg, Germany, in collaboration with the radiocarbon laboratory of the Curt-Engelhorn-Center Archaeometry in Mannheim, Germany. Here, we report an update of the technical details, focusing on the analysis of cold-water corals (CWC), and present an improved long-term blank value with a mean of (0.190 ± 0.064) pMC (n = 138) and excellent reproducibility of the IAEA-C2 standard with a mean of (41.15 ± 0.16) pMC (n = 75), consistent with its certified consensus value. Furthermore, 33 duplicates of the CWC 14C measurements agree within 2σ, 85% even within the 1σ range. This provides excellent conditions for accurate 14C measurements. As an application example, we present combined 230Th/U and 14C ages of a coral-bearing sediment core from the upper Mauritanian slope. The resulting ventilation age record confirms decreasing ventilation between 30 and 25 kyr BP, most likely reflecting a northward propagation of a water mass originating from the south. During the LGM, we confirm a previously hypothesized southward displacement of the Cap Verde Frontal Zone. With the onset of the deglaciation, our record documents again an advance of a southern-sourced water mass into the subtropical North Atlantic. During the Bølling-Allerød warm period, strong ventilation fluctuations possibly indicate temporal influence of southern-sourced water.

Continuous long-term measurements of temperature, salinity and current velocity, have been recorded over 44 months at the Tisler Reef. The Tisler Reef is a 2 km long cold-water coral reef on the sill of the Kosterfjord, located in the north-eastern Skagerrak, Norway. The reef comprises principally Lophelia pertusa, at depths between 70 and 160 m, and is an important habitat for sponge, crustacean and fish species including a number of species of commercial importance. Analysis of the current velocity data has identified a number of features such as flow reversals. These reversals in flow direction are often associated with significant changes in bottom temperature. During the autumn months of 2006 and 2008, a series of large and rapid increases in bottom temperature were observed, with temperatures seen to rise by approximately 4°C in a 24 hour period on both occasions. The occurrence of the 2006 and 2008 events corresponded with the observation of mass mortality in the long-lived sponge Geodia baretti. Historical temperature records from the region suggest that these temperature shocks are uncharacteristically high. The temperatures observed at the reef exceed the typical short-term physiological limits of L. pertusa thus future temperature shock events may have a swift and negative impact on the cold-water coral reef ecosystems of the Skagerrak.

Lophelia pertusa, a cosmopolitan cold-water coral, offers potential for new palaeoclimate proxies. This study investigated its skeletal growth patterns to aid in this development. Corallite characteristics (calyx diameter, height, thecal width and banding) of L. pertusa sampled from oil platforms in the northern North Sea were examined. The mean distance between daughter polyps along a growth axis (27.4 ± 5 mm, SD) was equivalent to the estimated annual growth rate; hence, the polyps bud once a year. The majority of growth occurred in the first year when the characteristic trumpet shape of a corallite was formed, while the thecal wall thickened more consistently. Further examination of two polyps showed a dark growth band and centres of calcification along the full length of the inner theca, which represents early skeletal growth. Skeletal sampling adjacent to this area along sequential polyps shows promise as an annual chronology in these North Sea corals.