September 2011

On Friday the 23rd of September....

Jeff and Cathy present a description of hydrothermal plume sampling and analysis at the East Scotia Ridge vent sites in the Southern Ocean

On Monday 5th of September....

Jessy Klar will present:

Title:
Dissolved aluminium distributions in the Atlantic Ocean: three study areas

Abstract: While it is well accepted that oceanic primary production (and therefore carbon drawdown) relies on the availability of Fe and other trace metals (such as Zn, Cd, etc) it is important to quantify the sources of these elements to the surface ocean. Aluminium (Al) has no known function within living cells but is a very useful tracer to estimate atmospheric dust deposition, one of the most important input mechanisms of Fe to surface waters of the open ocean.

Here we present dissolved aluminium (dAl) distributions in the open ocean from three different study areas within the Atlantic Ocean. In first place three cruises were conducted in 2010 in the Irminger Basin Iron Study (IBIS) in the High Latitude North Atlantic Ocean (HLNAO). Subsequently, high resolution dAl seawater samples have been collected during two GEOTRACES studies, one in the South Atlantic Ocean (GA10, 2010) and one in the Tropical Atlantic (GA06, 2011).

Dissolved aluminium in seawater was analysed onboard with a Flow Injection method using pre-concentration of Al onto Toyopearl resin (AF-Che-650M) and detection through lumogallion-Al fluorescence (Resing and Measures, 1994; Brown and Bruland, 2008).

The distributions of dAl in these three key areas of the Atlantic Ocean indicate significant differences of supply rates. The analysis of this data should improve our understanding about the ongoing global biogeochemical processes in the ocean.

July 2011

On Friday 1st July....

Ben Russell will present:

Title:
Developing a rapid and efficient actinide and Sr-90 analysis facility for
contaminated land assessment.

and Jade Burraston will present:

Title:
Advancing low-level radionuclide analysis using HR sector field plasma
mass spectrometry.

June 2011

On Friday 17th June....

Chris Stevenson will present:

Title:
The flows that left no trace: investigating channelised large-volume turbidity currents that bypassed sediment without eroding the seafloor

Abstract:

Submarine channels are the main conduits for sediment transport in the ocean, from continental shelf to abyssal plain. Individual flow events can transport >100 km³ of sediment and deposit across vast areas of seafloor; these flows are therefore responsible for some of the largest sediment accumulations on Earth. Seafloor gradient exerts a major control on the ability of sediment flows to erode/bypass and transport sediment. In particular, recent work off Northwest Africa has highlighted the influence of seafloor gradient on turbidity currents passing through deep-water channels (e.g. Wynn et al., in press). We build upon these recent studies by utilizing a spatially extensive core correlation framework across the Madeira Distributary Channel System, offshore Northwest Africa. These shallow channels (~20 m deep) extend for over 700 km and connect two large basins that form part of the extensive Moroccan Turbidite System. Over the last 400 ka this system has been host to some of the largest gravity flows ever recorded on Earth, with run out distances exceeding 2000 km and volumes >150 km³. Excellent core control, coupled with a robust geochemical and chronostratigraphic framework, enables individual flow events to be documented in both down-flow and across-flow directions.

May 2011

On Monday 9th May....

Tommy Ryan-Keogh will present:

Title:
High Spatial Resolution Iron-Addition Incubation Experiments: Mapping Seasonal Iron Stress in the High Latitude North Atlantic

Abstract:

The Irminger and Iceland basins of the High Latitude North Atlantic (HLNA) are areas characterised by incomplete nitrate depletion in the summer and relatively low chlorophyll concentrations. The annual cycle of chlorophyll demonstrates a peak in the spring in proximity to shallow bathymetry, one of the possible major iron sources to the HLNA. It has been proposed therefore that a lack of iron sources to the HLNA may lead to the development of a High-Nitrate Low-Chlorophyll (HNLC) region in the late summer. Long-term (>24 h) and rapid (24 h) incubations, at a high spatial resolution, examined the response of the phytoplankton physiology to iron addition, enabling the detection of mesoscale variability in Fe limitation. The proxy ΔFv/Fm was calculated from the 24 h incubations, and is defined as the difference in the maximal photochemical efficiency of photosystem II (PSII) (Fv/Fm) between a nutrient addition treatment and the control treatment after 24 h of incubation. The greatest increases in ΔFv/Fm were found in the centre of the basins with less of a response over the Iceland shelf and Reykjanes ridge, which may be acting as a source of iron. These results confirm and map the extent of the development of an iron-limited HNLC ecosystem in the Irminger basin, with a seasonal development of iron and nitrate co-limitation in the Iceland basin. This is the first seasonal study of the HLNA and allows the definition of two contrasting 'biomes' within the HLNA based upon the differential responses to iron addition.

March 2011

On Monday 28th of March......

Morelia Urlaub presented:

"Using Finite Element Modelling to Assess Submarine Slope Stability"

Abstract:
Submarine landslides are not only a hazard for the offshore oil and gas industry or telecommunication cables at continental shelves, slopes or deeper water, but also have the potential to trigger tsunamis. They are much larger than their counterparts on land and occur on extremely low slope angles (typically 1-2 degrees). Initiation mechanisms for these slides are vital for their prediction but are poorly understood, and in-situ investigations are restricted by a hundreds of meters thick water column. One idea is that rapid asymmetric deposition of sediment on the sea floor causes high rates of overpressure in a low permeability and low stiffness material as typical for marine sediments. We use transient, coupled Finite Element analysis to predict how the stress state of a submerged finite 2 degree slope that is subjected to slow continuous, asymmetric loading, changes over time as well as to assess the stability of the slope. The model is used to investigate the emergence of slope instability for different permeabilities, giving insights into the field conditions necessary for the development of submarine slope failure by overpressure alone.

On Monday 21th of March......

Anya Crocker presented:

"Palaeoceanography and Gas Hydrate Stability along the West Spitsbergen Continental Margin"