Phototrophic carbon fixation rates measured in water samples from the Porcupine Abyssal Plains during James Cook cruise JC087

Water samples were collected from pre-dawn CTD casts at 5 depths corresponding to 55%, 20%, 7%, 5% and 1% of surface irradiance. 1 litre water samples wrapped with optical filters to replicate light levels. Spiked with 200 µL of 13C labelled sodium bicarbonate. After 24 hourse filtered through ashed 25mm GF/F (Whatman) filters, rinsed with HCl solution (1-2%) and stored at -20oC. On shore encapsulated in tin capsules and analysed for 13C isotopic enrichment. Carbon uptake rates calculated using the equations of Fernandez et al. (2005).

Heavy minerals, grain size distribution, and ice-rafted debris in the Greenland Sea during 44 to 30 Ma

The widely accepted age estimate for the onset of glaciation in the Northern Hemisphere ranges between 2 and 15 million years ago (Ma). However, recent studies indicate the date for glacial onset may be significantly older. We report the presence of ice-rafted debris (IRD) in ~44 to 30 Ma sediments from the Greenland Sea, evidence for glaciation in the North Atlantic during the Middle Eocene to Early Oligocene. Detailed sedimentological evidence indicates that glaciers extended to sea level in the region, allowing icebergs to be produced. IRD may have been sourced from tidewater glaciers, small ice caps, and/or a continental ice sheet.