The Mid-Atlantic Ridge

At the northern end of our travels we are looking at the Bear Island Fan. This is one of the largest packages of fan sediments in the world. It extends from the continental shelf just south of Bear Island westwards to the Mid-Atlantic Ridge (MAR). We wanted to see if any of the debris flows that make up the fan reach the centre of the MAR. This gave us an opportunity to survey along this dramatic structure to see if there was a suitable site to sample. First as we approached the ridge we could see on the 3.5kHz pinger records blocks of rock protruding through the well layered sediments. The multibeam showed that these blocks were parallel to the MAR and increasing in height and extent as we moved towards to the actual ridge.

Then we reached the ridge itself. As we steamed along its axis with Pelagia’s  starboard side above the European Plate and its port side above the American Plate the multibeam display was a confirmation of all those sketch diagrams on plate tectonics explaining the formation of oceanic crust at spreading centres, with each line of multibeam data added to the swath showed ridges parallel to the axis or evidence of volcanic activity. The ridge exhibits sudden large changes in bathymetry that makes following the seabed on the 3.5kHz pinger involve frequent changes of the display offset. It showed the rocky seafloor but we could see no thick sequences of sediments so we moved away to investigate the debris flows at the edge of the Bear Island Fan only a short distance to the east where we recovered a 10m long core with a very good record of the Bear Island Fan. 

Image from the Swath multibeam onboard the RV Pelagia of the Mid-Atlantic Ridge.

David Long

Trænadjupet Slide

So we've heard about the Afen Slide and seen some of the great cores from the Trænadjupet Slide, as well the wide array of sediment types that exist within them. Here's a little background on why the Trænadjupet Slide is important and what the cores might tell us.

Extent of the Trænadjupet Slide (Courtesy of SpringerLink)

We know from recent submarine landslides (Grand Banks, 1929), and from the geological record (Storegga, ~6000 BC), that submarine landslides have the potential to cause tsunami evens similar to the 2004 Christmas tsunami in the Indian Ocean. Despite this tsunami-causing potential, the Trænadjupet Slide appears to have left little or no evidence of a tsunami on nearby coastlines as one might expect. Tsunamis often deposit marine sand much higher up on land than normal coastal processes and thus we have a record of the event stored for us to study. There are some potential deposits being explored, but there is still some debate about the significance of these deposits. Much of the uncertainty arises due to a lack of sufficient age-control on when the Trænadjupet Slide took place. Uncertainty also surrounds how fast the collapse happened and how fast it moved.  Fast moving landslides will tend to have more of an impact than those that move slowly or those that fail in multiple smaller stages. 

Schematic of how underwater landslides can cause tsunami waves (Courtesy of IranPetroTech)

So, where do the cores come in? Cores will be used to radiocarbon date marine background sediment which has accumulated on top of the landslide debris, and help constrain how old it is. Cores also allow us to look at the internal morphology of the slide and how the debris is distributed both spatially and in time. If the slide took place in numerous small stages rather than as one large failure, it may not have had enough energy to create a tsunami. The cores and radiocarbon dating will help us to better understand why this slide might not have generated a tsunami which will assist in assessing the tsunami risk to countries with nearby continental margins. 

Tsunami deposits within terrestrial soil on The Shetland Islands

Josh Allin

Progress in the Far North

After a successful coring campaign to date, and the continuing excellent weather, we are now moving towards our most northerly site at 74° north. We have now collected over 300m of piston core from a range of sites in the Nordic Seas, and are now focused on collecting samples that will help us to understand the timing of deposition of sediments on the Bear Island Fan. This feature is one of the largest depositional formations on earth, and we are hoping to understand the timing of sediment delivery to the slope, and hopefully this will inform our research on slope stability.

The weather has made a turn for the worse, we currently have 5-6 meter swells and the temperature feels truly "Arctic" today, so much so that we experimented with the survival suits and the padded thermal boiler suits whilst working on deck this morning!

The night team in their warm gear

Enjoying the spray at the end of our shift

Glorious Mud.

We have been coring in the Traenadjupet region, and have seen some fabulous examples of a range of processes recorded in the mud. We are hopeful for some great results from these cores, though this will take some time to work up, but in the meantime, here are a few examples of some of the wonderfully colourful and exciting mud cores we have taken recently:

This layer has been described as the Pistachio Green horizon after its distinctive colour. This was the first core we found it in, though it has appeared in several others. The exact chemistry and mineralogy of the layer will be part of the post cruise work, but this is an unusual colour, and will unfortunately fade over time.

This very unusual deposit looks remarkabaly like a butterfly, but is in fact a series of mud boulders that were caught up in a submarine landslide. The mud would have been partially consolidated at the time, and the layers ripped up and rolled into boulders, which we have then cored through.

This picture is a close up of one of these contorted mud boulders, and shows that the sequences of colours is symmetrical across the pale brown horizon. When interpreted as having symmetry, andthe fact that these layers terminate against the side of the core, we can be sure that they are boulders of mud and not an artefact of the coring process, which can sometimes cause disturbance to the layers, as seen below:

The darker mud visible in the centre of the core is running from top to bottom, and there are very few processes that can produce this type of feature. It could be bioturbation, the traces left behind by burrowing fauna that are infilled by sediment, but in our current location in very deep water, this is too large a burrow to be possible. This is unfortunately a product of suction at the base of the core, which can cause mud from the base to be injected upwards into stratigraphically higher layers. This limits the usefulness of the core, but is normally confined to the lower sections.

The unusual black block in the lower core is a boulder of peat that was caught in the flow. It is surrounded by clasts of mud set in a sandy matrix, typical of the type of deposit left by a large submarine landslide. The peat boulder is spongy and soft, and will be useful for us to determine where the flow originated as it should contain macrofossils and pollen.

This wonderful striped section is from a deep basin core, and each of the layers represents a very distal deposit from the submarine landslide. Cores like this one have the deposits separated by a thin section of hemipelagite: "normal" marine sedimentation whcih contains forams and potentially other material that will allow us to date each event. These long basin records are one of the key objectives of the project, areas that capture a long record will allow us to assess how frequently landslides happen, whilst the cores taken on top of the landslides are helping us to understand what makes some landslides tsunamigenic or not.

This final picture shows some very pretty laminations, couplets of sediment that will be part of our research into sedimentation patterns on the margin. They appear only in certain locations and within small sections of core, and are potentially the result of seasonal/cyclic changes in sediment source or the energy of the current.

Millie

The triggers

68.5^oN 8^oE

Notes: Sun has now not set for three days, although the weather has been overcast for the last two days. Graveyard shift currently leads the daytime shift by 17 to 11 cores, not that we are counting. Alessandro is pretty poor at darts. There is a storm coming!!!!

Core Puns:

He who dares.....Cores

The Good, the Bad and the Corer

Cora! Cora! Cora!

The Italian Core

Return of the Corer

Cool Coring

The Beauty and the Corer

101 Cores

Core Story

Harry Potter and the Half Sand Core

The Core

Reservoir Cores

One of the purposes of the 2014 Pelagia Cruise is to collect information relating to the triggering of submarine landslides. Many possible triggers for submarine landslides have been identified. These include earthquakes, rapid sedimentation and gas hydrate dissociation. Working out the specific triggering factor behind individual slides is, however, extremely difficult. Which factor has preconditioned the slope to failure? Which factor has triggered the actual slope failure? Today I was covered in 4000 year old mud by certain members of the night shift (Camilla Watts), what the actual reason for this is unclear [Editorial note: it was well deserved]. Was it the fact that I was inanely putting the word core or corer in film and book titles for two hours? Was it because I thought Harry Potter deserved to be kicked in the shin or because I have never watched or am not likely to watch Game of Thrones? Or was it because I have been talking constantly about ball sports for the last year? Or was it that she randomly got bored and decided it was a good idea?

Although a submarine landslide will not be triggered by a poor pun this example indicates the complexity of the question that we are attempting to answer. Many of the submarine landslides around the Norwegian Basin are closely associated with the numerous trough mouth fans which line the continental slope. These features are produced by ice sheets. Glacial ice is a much more effective erosive agent of sediment and bedrock than rivers and is therefore able to deliver extremely large volumes of sediment to the continental margin very quickly. Rapid sediment loading from ice streams (areas of extremely fast flowing ice) is thought to lead to high pore pressures and instabilities which could lead to failure. Similarly dissociation of gas hydrates, an ice like crystalline structure, into their gaseous constituent parts can also generate high pore pressures which could lead to failure of the sediment. Dissociation of gas hydrates can be caused by a number of factors. These include pressure changes related to changes in sea level and temperature changes caused by ocean warming and cooling. Whilst these factors could trigger a submarine landslide, they could equally precondition the slope to fail.

Where rapid deposition of sediment gas hydrate dissociation has generated a slope preconditioned to fail a further trigger may be needed in order to actually achieve failure. In many cases this trigger is an earthquake. Shaking of the sediment can lead to a loss of structure and subsequent failure. Large magnitude earthquakes are currently relatively rare around the margins of the Norwegian basin. However, as we moved out of the last glacial period earthquake magnitudes in this region increased in response to glacial unloading of the crust as the ice sheets retreated. These earthquakes may therefore have represented a common trigger for many events. Despite the increase in magnitude of earthquakes associated with crustal rebound, not all earthquakes will cause slope failure to occur. Some might even lead to a strengthening of the sediment and reduced likelihood of slope failure.

I hope from this post that it is clear that isolating an individual trigger for large submarine landslides is extremely difficult and presents one of the main questions to be addressed as part of the landslide tsunami project. Only with precise dating of the landslides will we increase the possibility of linking landslides to individual triggering mechanisms, although this may in fact be impossible. Who knows?

Ed Pope

 

Progress so far…

We have had a really successful coring campaign so far, after three days of fairly intensive activity we have collected over 20 cores, from a variety of sites. One of our first objectives was to core both inside and outside a set of large cracks close to the Storegga Slide, these features are over 100m wide, and have not yet been reliably dated. The cores we retrieved we quite spectacular, with abundant carbonised material and several distinct horizons that will allow us to correlate the cores, and refine the date at which these cracks formed. 

James and Matthieu assessing a core during the night shift.

As we moved north over the Voring Plateau, we crossed a large pockmark field, which is the subject of current research at NOC. We managed to collect two 12 m cores here, one from within a Pockmark and one from the adjacent sea bed. The pockmark core still contained small amounts of methane clathrate when it was cut on deck, nice to see as we had expected in to have dissociated before reaching the surface, however, they have a particularly unpleasant to smell!

We are currently in the Traendajupet region, looking at the nature of the landslide here, and hoping to collect a variety of data to help us understand how the landslide moved, when it happened and how much material was involved.

Life on board has settled into a steady rhythm of shifts, to maximise our time at sea we are split into two teams, the night shift run s from midnight to noon, and day shift for the opposing 12 hours. We have three meals a day, though the night shift tends to sleep through dinner, and the same for the day shift at breakfast. The chef of board is fantastic, and we have been spoilt with food, our main meal is always at lunch time, normally a soup, main and desert, and he leaves the night shift something tasty in the fridge for when we get hungry in the very early hours of the morning, the lasagne was definitely a high point!

We have a daily science meeting at midnight on the shift change, to catch everyone up on the plans for day, where we are surveying and how many cores to take in each location. We have several intense days of work between now and Wednesday, and though we have been fortunate with the weather so far, this is likely to change on Sunday night as a storm heads our way, however we are not expecting anything too severe.

The plan for the next week is to continue to the northern edge of our study area, hopefully with as much good luck as we have had with the cores to date, before heading back towards Iceland, then back into Bergen for the 31^st. 

Big things in small shells

Contrary to popular belief, euphemisms, idioms and trite sayings often have little relevance to real life. Foraminifera on the other hand, lend credibility to the notion that big things do indeed come in small packages.

Foraminifera are small single-celled marine organisms; more specifically known as Protists. They exist at various depths within the oceans but are most commonly found in shallow waters above 50 m. Many feed on small marine plants and other detritus, but some are carnivorous and feed on other smaller species. They have lived in the oceans for millions of years and are found throughout every ocean on Earth. This fact makes them remarkably useful in studying ancient oceans.

Many species construct their shells out of calcium carbonate (CaCO₃), while others construct it using fragments of other shells, or even grains of sand. The CaCO₃ which makes up the shell contains a record of a large number of environmental variables which can help us understand the past ocean. Carbon and Oxygen both have 2 stable isotopes (¹²C, ¹³C, ¹⁶O and ¹⁸O respectively). The record of past changes in these isotopes locked in these Foraminifera shells can be used to infer changes in water mass distribution, changes in ice volume on land and nutrient distribution in the oceans. 

Aside from basic stable isotopes, Foraminifera also contain record radioactive isotopes. One of these isotopes called radiocarbon (¹⁴C), is particularly important to paleoceanographic studies. When Nitrogen 14 (¹⁴N) in the upper atmosphere is bombarded by incoming solar radiation, it gains a proton and becomes ¹⁴C. This radiocarbon diffuses into the oceans and is taken up in small amounts into the shells of the Forams. By measuring how much of this radiocarbon is left in an ancient shell we can know its age and the age of the sediment which surrounds it. This helps us tie down the ages of important ocean events like landslides and ice-sheet break-up.

Several additional proxies exist including Uranium decay series elements. These are used to detect the source of water masses by using their chemical fingerprint to trace the source of their terrestrial suspension material. Even the numbers of Forams can help us. Certain species thrive in cold water while others prefer the warm waters of the sub-tropics. Using the % of these different species in a sediment sample, we can compare this past assemblage with modern ones and infer sea surface temperature changes that help us understand de-glacial events

To sum up, these guys may only be the remains of tiny dead critters, but they provide us with a immensely powerful tool in our quest to understand the oceans and their role in the changing climate.

Josh Allin

A-Level Science and Geography Post

As part of some outreach in June, the cruise team took part in a visit day from a Somerset sixth form college, Richard Huish, who came to the National Oceanography Centre for a series of talks about our on-going research. As part of their visit day, they had a lecture from Dr. James Hunt on the history of landslides from the Canaries, and a visit to the core store (BOSCORF) to see several cores and get an overview of how we interpret landslide deposits. This post is aimed specifically at students during their A-Levels, and hopes to explain the science we are working on within the context of the A-Level syllabus. If you are taking your A-Levels at the moment, please take part in our Q and A on the “Chat to the Team” post; we would love to hear from you!

Part of the A-Level geography syllabus covers tsunamis as a hazard in addition to climatic hazards that affect the UK. Though most case studies focus on the recent earthquake induced events in Indonesia and Japan, though it is worth remembering, that over the Holocene (the most recent geological time period spanning 12000 years ago to present), several landslides have occurred on European continental margins that had the potential to generate tsunamis that would affect the UK. The Arctic Landslide Tsunami Project is playing a key role in working out how much of a hazard submarine landslides pose, and when or if they are likely to occur.  

Shot of dawn from the Pelagia while winching back the CTD (Conductivity, Temperature Depth: measures the characteristics of the water column)

One of the biggest research questions of the Arctic Landslide Tsunami Project, is to assess the link between when these landslides occur, and the climate at the time. This is largely driven by one of the biggest coincidences in timing between two events that occurred approximately 8200 years ago: the Storegga Landslide, and the 8.2 ka BP cooling event.

The 8.2 event was the last of the major climatic shifts to occur, though there have been several others (the Younger Dryas event is a case study within the Climate module, during which time half of the deglacial warming occurred in year (almost 10-12°), at 8.2 ka, a 5.4-11.7° C drop in temperature over Northern Europe occurred in less than 10 years). The 8.2 event is interesting to climatologists as it occurred during a period of relative warmth and stability. During glacial periods, there are numerous records of rapid and large climate shifts known as Dansgaard-Oeschger cycles, which follow a pattern of slow cooling and rapid warming, but few rapid climate shifts are known from the warmer interglacial periods.

Why this matters, is that we are currently in a warm period, not too different to the conditions just before the 8.2 event, and we need to understand not only what triggered the event, but also, the other hazards that were potentially generated by it. The widely accepted theory for the cause of the 8.2 is that an ice dam that had been holding back a large volume of very cold fresh water, generated by the melting of Laurentide Ice sheet (covering North America during the last glacial) suddenly broke, and released this water into the North Atlantic. The North Atlantic is one of the most important components of the global climate system, as the formation of deep water in the Nordic Seas and to the south of Greenland helps drive the northward flow of warm water held within the Gulf Stream that keeps the UK nice and warm.

The second event, the Storegga Landslide, is the largest known and dated submarine landslide in the North Atlantic, and has been placed at 8.15 ka BP. Though this is a hard date to refine, it falls exactly within the coldest period of time recorded in the Greenland Ice records (8.16 ka BP). The landslide generated a tsunami that was 10 m high when it reached Scotland and the Shetland Islands (comparable in height to the two recent tsunamis), and tsunami deposits have been found along the Norwegian coast and as far afield as Greenland. The landslide itself moved enough sediment to cover all of Scotland in a 100 m thick layer, and an event of this size today would cause significant damage to UK industry and infrastructure, and represent a significant risk to the large oil and gas operations in the North Sea (The headwall of the Storegga Slide is very close to one of the largest complexes: the Ormen Lange field, which was subject to a comprehensive assessment of stability and landslide frequency in 2005 before operations began).

Landslide events are recorded as turbidites, distinctly different layers of silt or fine sand in an otherwise muddy (hemipelagite) background, by looking at the nature of the material in the turbidites, its size, chemical composition, how well sorted it is and the structures it shows, we can tell where the landslide came from, how old it is and whether or not it happened in one big slide (likely to generate a tsunami) or in several smaller slides from the same region (less tsunamigenic potential, but still likely to cause a hazard).

The key question for my PhD, is looking at the timings of these two events, in order to determine if there is a relationship between them. Did the cooling cause the landslide, or did the landslide contribute to the cooling? Are landslides caused by rapid changes in the oceans? If so, are we more likely to see one happen with contemporary global warming?

These questions can only be answered by heading to the deepest parts of the Nordic Seas, the Lofoten basin, and to the parts of the ocean floor that sit directly beneath the deep water currents. This current is generated by the sinking of water in the Nordic Seas, where it splits and part heads north along the Voring Plateau margin towards the Barents sea, and part heads south over the Iceland Scotland Ridge, a shallow sill of 800 m water depth where we are hoping to collect a core that records the strength of this current, and any landslide events that occurred over the Holocene.

If you have a question, A-Level student or not, please feel free to join in the live chat next week, and keep an eye on our other social media streams:

Twitter: #ArcticSlides

Pinterest: http://www.pinterest.com/millie0692/arctic-landslide-tsunami-project-pe391-cruise/

Millie

The Afen Slide

As scientists have explored the seafloor they have often found evidence of submarine landslides on the continental margins. In many cases the seafloor topography is quite complex, the consequence of multiple sliding events making interpretation of what has happened difficult. On the slope northwest of Shetland there is a small landslide on its own which we hope that by studying it in detail we can contribute to studies of larger, more complex slides.

The Afen Slide is found between 850 and 1100 m water depths, where the slope is only 1-2° but the failed sediments have spilled out upon the floor of the Faroe – Shetland Channel below 1000m. It covers an area of 40 km², which is about half the size of the city of Edinburgh. The slide cuts about 20m into the soft sediments of the West Shetland slope and displaced a volume of   ~ 0.2 km³.  

It is important for us to determine when this slide occurred and what its trigger was. If it had occurred towards the end of the last Ice age when ice-sheets were melting, causing an unloading of the earth’s crust with earthquakes greater than are experienced now; then the risk of a similar event today would be very low. However if it can be shown that it is a recent sliding event then another slide might be expected in the current environmental conditions. We hope by sample the sediments that slid we can understand how strong they were and type of event could have caused the slope to fail. 

David Long
BGS

Musings from a boat

Day 2.7

Notes: Spent the last 12 hours asleep. Now acclimatised to the graveyard shift. Watching the sun set and come up is epic but its called the graveyard ship for a reason. Dinner – salmon fillet, mash potato, green beens and magnum ice cream. Hair – poor. Tan – limited to face. Wildlife seen – two whales, dolphin pod, sea birds and Sheltlands. Rowing machine 1 Millie Watts 0 #cruiseproblems.

Thoughts from 60^oN.

Whether we are following quite in the footsteps of the likes of Sir Humprey Gilbert, Robert Peary and James Clark Ross, the landslide tsunami project cruise onboard the R. V. Pelagia nevertheless seems to combine many British traditions. We are following both our tradition of Polar exploration whilst using the most important of British ideals, our ability to muddle through. We have also commandeered a foreign vessel, a very British practice since the 15^th and 16^th Centuries.

Progress has been relatively slow. So far we have spent our time speeding at 10 knots towards the Afen slide. There has a lot of heaving, pitching and rolling; the boat not the scientist trying to sleep who have forgotten their sea sickness medication. The transit past Scotland has been marked by drizzle and rain. We have also found that the motion of the boat adds an extra dimension to our attempts at darts and table football. Using a dial up connection is far more efficient for procrastination than broadband as you have to wait ten minutes for each page to load. Salt which has crystallised on the deck is a distinct problem for GoPro suction cups.

What can we expect in the future. Larger waves. Longer and longer hours of daylight. Small disagreements turning into full blown arguments. Holland vs Germany in the WC final? More erratic blog posts.  

Ed Pope

Mud, Silt and Sand

So, when I said to a couple of people that I was heading off on a research cruise to the Norwegian Sea, I got responses of 'Oh how lovely, the fjords are supposed to be beautiful'.  I am sure that the fjords are exceedingly picturesque, but the likelihood of seeing them is a prospect that might only happen from a helicopter, and hey, let's not go there!  We, the team of ten scientists from the National Oceanography Centre, Southampton, Swansea University, BGS Nottingham and BGS Edinburgh are going to do something even more exciting... We are going to come face to face with mud from the sea floor that is thousands of years old, and which flowed down the continental slope (the rise between the deep abyssal plain and the shallow shelves, the ancient relict of palaeo ice margins) as mighty bulldozers in the deep – large submarine debris flows and turbidites.  But why is this exciting?, I hear you ask. Well, let me tell you why.

Mud, silt and sand (aka. sediment) are deposited in layers on the sea-floor.  They form from admixtures of organic and inorganic matter (soft and hard parts of living organisms), and sediments that either settle through the water column that could have been derived from rivers, or remobilised by deep ocean currents.  These layers of mud build up over time and often contain fossilised remains of past environments.  Protists (animal-like, single celled organisms) called foraminifera have a hard calcitic (the same substance that limestone is made from) test (shell: see below) and can be found today pretty much in every ocean basin.  These live either at the surface or and the bottom of the ocean.  Their tests take on the geochemistry of the ambient sea water as they grow and different species, which are distinguished by their different shapes are fussy about what temperature of water they live in.  Information on the ocean environment can also be obtained from the physical characteristics of the sediments themselves, which may give clues to the ice-sheets that abutted the ocean basins.  Therefore if we core through this layer-cake of sediment, we can obtain a record of environmental change in the ocean through time (see next blog post for more details). 

Scanning Electron Micrograph of a Planktonic Foraminifera (Photo J. Stanford)

Occasionally, these layers of sediment can become very thick due to high rates of sediment being delivered to that particular area. One such site was just west of Norway, not now, but around 18 – 14 thousand years ago.  During this time, the ice-sheet that covered Norway during the peak of the last ice-age was melting rapidly as the air temperatures in the Northern Hemisphere started to warm.  Ice contains large amounts of sediment, which have been worn away from the bedrock that the glacier once flowed over.  Today in the Arctic, ice melt tends to happen during the relatively short summer season, and in the past, mixtures of meltwater and sediment would have been injected into the Norwegian Sea as highly sediment laden plumes.  The sediment may have entered at the surface, or may have been injected as periodic, highly dense flows.  These high density flows which form from a steady pulse of sediment laden waters are called hyper- (super) pyncal (density) flows.  Sediment from the last deglaciation (18-14 ka BP or so) accumulated in piles, which today is seen as a <25 m thick sediment drape over much of the Vøring Plateau.  These sediments became unstable over time due to one, or a combination of three key factors (1)  due to gravity (just like when you are digging a hole in the garden and eventually the sides become so steep the mud collapses back in), (2) the shear weight of the sediments causing loading of the thin rigid crust that covers the Earth, triggering earthquakes and/or (3) organic matter, trapped within these sediments started to decompose over time within these thick deposits, releasing gas that escaped through the sediment pile.  Eventually, a crack would have propagated from deep within the sediment pile, all the way to the sea-floor, spawning what is known as a submarine 'gravity flow'.  Depending on whether the sediment flowed downslope as one block, or whether it disintegrated into a much more fluid flow, defines whether these flows as a debris flow or turbidity flow, respectively (see http://www.youtube.com/watch?v=krVkYvJI-PI for a visual demonstration of what a turbidity flow looks like and future blog post).

As these sediments fail and rush down the submarine continental slope, they displace the sea-water around them, giving rise to the possibility of powerful and destructive tsunamis (a recent example of this can be seen in Lituya Bay).  One such failure on the Norwegian margin, is known as the Storegga Slide, which mobilised around 900 km3 of sediment and occurred around 8 thousand years ago. It is thought that there are tell-tale traces of this large tsunami that resulted from this failure as far afield as the Shetland Islands.  However, the exact timing and nature of this event is still unsure, despite decades of research. Other slides include Andøya and Traenadjupet (~4 thousand years ago), and Nyk (~16 thousand years ago), precise ages are also still unsure for these.

There is a need to know what caused these large failures in order to mitigate against future catastrophic events, since large accumulations of these sediments still exist on the Norwegian margin today, as a relict legacy of the past cold climate that persisted between throughout the last ice age.  What makes Storegga even more interesting is that fact that its failure roughly coincided with an extreme cold snap in Northern Hemisphere temperatures around 8.2 thousand years ago and therefore, we need to untangle whether abrupt climatic change has a role in destabilising the sediments.  Given that global temperatures have on average risen by 0.72 degrees Celsius since 1951 (IPCC, 2013), and that this change is not uniformly distributed, with enhanced warming in the polar regions (a process known as polar amplification), increased urgency surrounds this need to discover the mechanism behind these potentially catastrophic events.  A series of other, much smaller, but still large failure scars can be seen on the Norwegian sea floor and previously recovered cores of sediment have dated these events as having occurred at intervals during the current warm period, the Holocene that followed the last ice age.  So, we are heading to these sites to try to discover (a) how and why these large failures occurred, (b) when these failures occurred and (c) what were their impacts.  That is why we are excited about going to the Norwegian Sea for some very hard graft, but some really rewarding returns!

Jenny.