Dendrochronology Glen Affric, 2014

Scot 2k - Dendrochronology, Highlands, 2014

Scot2K – a dendrochronological project the Scottish Highlands (NERC (NE/K003097/1)) that aims to push back the high resolution climate record of the Scottish Highlands back 2000 years.  It has both local (UK) importance and will also contribute to the wider climate record of Northern Europe and Northern Hemisphere.Growth of Scots Pine trees in the Scottish Highlands is predominantly controlled by growing season temperatures. Using parameters measured from tree-rings (i.e. ring-width and density) it is possible to derive estimates of past summer temperatures. However, the mean age of most pine trees in the Cairngorms is around ~225 years. Therefore, to derive climate estimates prior to ~1750, information must be gleaned from older preserved woody material.

Where to find this material?  Well thankfully, Scotland is not without its lochs and it is into these that many of the older trees have either fallen or have been felled.  Finding these trees and then sampling them was the goal of a recent trip to Glen Affric. The team, under its climate warrior leader, Dr Rob Wilson, had previously scouted out (swimming with snorkels)  some of the small lochs. Others were known from the Trees for Life project (http://www.treesforlife.org.uk/).

The UK team, including individuals from Sweden and Switzerland (Dr Richard Bates, Dr Cheryl Wood , Stacey-Anne Averill, Dr Mark Neal, Dr Björn Gunnarson, Dr Neil Loader, Dr Daniel Nievergelt, Dr Coralie Mills) arrived in Glen Affric armed with dry suits, saws, corers and a new remote-control survey boat.  The boat, built by students at Aberystwyth University Computer Science Department contained a 900kHz sidescan sonar and GPS logging to small laptop in a hull that was sufficiently small  to be back-packed into some of the more remote lochs.  This was considerably easier than trying to get either of our previous survey vessels, the Zego Boat or Minty (see previous blogs for both) onto the water.  Why use sonar? Well if you have ever swam in an upland loch you would know how murky the peat-ladened waters are that restrict visibility to a few centimetres.

Processing of the sidescan sonar data was using Chesapeake SonarWiz and ultimately data display within GIS.  Targets were identified and the dive team went to work.  Many of the sites contain vast numbers of trees but many are in too deep water or are too far from the shore for recovery (usually an operation using wire cables and winches attached to living trees on the loch shore).  Many of both living and dead tree root structures were visible on the sidescan records as were very curious sinuous features that we have so far been unable to identify due to the murky water.  These are likely branches.

At the end of the week the team had found and sampled over 150 trees – a highly successful hunting trip.  Now for all the analysis though and a hope that the material will contain sufficiently old records to push back the dendro record.To date, 661 sub-fossil pine samples have been collected from lakes in the NW Cairngorms: Loch Gamnha (215), Loch an Eilein (293), Green Loch, Ryvoan (67) and multiple lakes in Abernethy (86) - about a third of which have been dated using radiocarbon dating or tree-ring (dendrochronology) methods. However, dendrochronological dating of the samples has been a challenge. It has become clear that the impact of human disturbance (related to tree felling) has had a profound influence on the growth of the trees which decouples tree-growth from climate. Although these human based disturbances impact on the potential climatic information that can be gleaned from these samples, an unplanned outcome of this work will be the detailing of the human timber extraction/land-use history (likely a part of the Highland Clearances story) of the regions sampled through the Scottish Pine Project (i.e. the native pine woodlands). A network of over 50 pine woodland sites have now been sampled across Scotland (http://www.st-andrews.ac.uk/~rjsw/ScottishPine/). This is an exciting outcome as it will allow a new appreciation of the impact of logging on pine woodlands and their resultant recovery over multiple centuries.

Tree-ring based reconstructions of past summer temperatures are still in development. Through Milos Rydval's Carnegie Trust funded PhD project, Rob’s team have spent a substantial amount of time developing the new Blue Intensity (BI – a proxy of lignin content and cell wall thickness of the latewood) parameter (Rydval et al. 2014; Wilson et al. 2014). Utilising both RW and BI data from Abernethy, Green Loch, Loch an Eilein and Loch Gamnha we can already produce a well calibrated (55% of the July/August temperature variance explained) temperature reconstruction back to AD 1460 (see Figure).

Christchurch - Priory and Mill
While down at Stonehenge (more on this to follow shortly with a press release on Sept. 11th) I managed to spend a morning with an old friend, Peter Fenning, helping out with some local archaeological sites in Christchurch.  In particular, we ran a frequency domain electromagnetic survey over the grounds around Christchurch Priory.  For this we were using the CMD Explorer with gps positioning.  Initial results were very promising with what looks like a signature for the main site well showing up as a very strong anomaly.

The figure above is for the deep conductivity (down to 6m).  We still have to process the data and integrate it with the rest of the site information so more to follow later.  In the mean time follow the Christchurch group at: http://christchurchantiquarians.wordpress.com/blog/

Floodplain hydrology and geophysics in France: by Cristina Evans

In June 2014 we (Cristina Evans, Richard Bates and Chris Sargeant) travelled to the south of France for fieldwork. Our three sites were located along the Rhône River, at Péage-de-Roussillon, Donzère-Mondragon and Mas-Thibert. Didier Graillot and Frédéric Paran from the École Nationale Supérieure des Mines de Saint-Étienne joined us in the field and assisted us with obtaining hydraulic conductivity readings using a Guelph Permeameter. We also collected soil water samples and electromagnetic readings. This data will help us to characterise the soil structure and hydraulic properties at our sites, to understand the subterranean hydrology in the riparian corridor. 

The following video tells the story of our trip. I hope you enjoy it!

http://www.youtube.com/watch?v=3RmNHGgVxJo

Cristina

Operation Iceberg

Operation Iceberg and other fun in Greenland - over the last few summers I have been working with a number of colleagues up in Greenland.  It's the best kept secret holiday location if you want stable weather, blue skies and 24hrs of daylight.  Rather than blogging here I have written a short piece for the "Travelling Geologist" - Chris Spencer - check out some of his great blogs on http://www.travelinggeologist.com/

richard 

Peering inside volcanoes: A guest post by Oliver Lamb

Picture yourself here. You are a scientist monitoring an active or erupting volcano. In the past, this volcano and others like it have produced lava domes which are prone to suddenly and violently explode or collapse to produce devastating pyroclastic flows, often without warning. Unfortunately, it's this sort of behaviour by Sinabung in Indonesia that recently took the lives of 14 people (see the video below for a spectacular example from Sinabung). So what can you, as the scientist, use to work out when the growing dome is going to explode or collapse next? What is already known is that the transition from quiet to violent activity during dome growth is because of a complex range of processes, particularly before explosions.

Fortunately for scientists like me, active volcanic systems produce a wide range of seismic signals prior to and during an eruption and these signals are easily picked up by seismometers deployed around the system. For my PhD at the University of Liverpool I am carefully analysing the seismicity from recent or ongoing dome-forming activity, focusing particularly on any signals that can tell us something about the conditions within the volcano before explosions or dome collapses. Hopefully by the end of this project, I will have looked at seismicity from at least four different active volcanoes: Volcan de Colima, Santa Maria, Mt Unzen and Mt. St Helens.

'Drumbeats' recorded over a 24 hour period at Mt St Helens, 15 November 2004

To give you an idea of the size of the dataset for this project, I've included the snapshot above of the seismicity from Mt St Helens during its eruption from 2004 to 2008. What you're looking at is the seismograph from a single day during this eruption, and each of those peaks is an individual volcanic earthquake. Now imagine trying to analyse each event, every day, every month,  for well over a year, then you have a gigantic number of events to look at! Thankfully, at least for my sanity, we have tools which we can use to automatically count all these events and measure different traits about each event. These traits include how big the event was, how long it lasted for, how long was it since the last event, the frequency content and much more. With these tools, we can now begin to track how these events change over time and begin to get a better idea of what's going on as the eruption progresses. I have already used the tools on seismicity from  Mt St Helens, and by my latest count the volcano experienced well over 500 000 seismic events from November 2004 to March 2006, an average of around 50 events per hour. I hope that emphasises how large the dataset is!

Left: Volcán de Colima, Mexico, during more peaceful times, taken August 2012.
Centre: Mt Unzen, Japan, nearly 20 years after it ceased erupting. (Credit: J. Kendrick, Liverpool).
Right: Santiaguito, Guatemala, taken December 2007. (Source: photovolcanica.com) 

But the project doesn't stop there. There are plans afoot for a whole raft of other analytical methods to be used. Methods such as locating each event as the eruption progressed, looking for events which may have come from the same source, and then some statistical analysis on top of that. Eventually, armed with all the geophysical results, my project will then begin the experimental phase. During the experiments, I will be placing samples into similar pressures and temperatures as we think the seismicity is being produced in, and break the samples apart and record the resulting acoustic emissions. The current idea is that by the comparing the experimental and volcanic waveforms, we can then help figure out what's going on inside the volcano during a dome-forming eruption.

The author, on the south flank of Volcán de Colima in July 2012

There you go, there's my project in short. For those of you who don't know me, I'm Oliver Lamb and I am a first year postgraduate research student with the Department of Earth, Ocean and Ecological Sciences at the University of Liverpool. If you have any questions or comments about what I've written here, then please feel free to get in touch with me via e-mail, olamb245@gmail.com, or find me on twitter, @olamb245. Thanks for reading!

Iceland - Orca 2014

Grundarfjörður

Iceland - Orca 2014

Iceland - a change of scene and most definitely a change in temperature since Tanzania!  I have spent the last couple of weeks working with the University of St Andrews Sea Mammal Research Unit (SMRU) on a project led by Dr Patrick Millar  investigating methods for measuring and monitoring the health/body condition of cetaceans, in this case, orca. 

Orca off the bow

Our part of the project will be testing sonar as a tool for specifically measuring body condition from body measurements.  This might seem like a far cry from mapping seabed or reconstructing palaeo-landscapes, the more usual deployment of sonar in my work, but really it’s not such a far cry.  The idea is to use a new generation of very high resolution sonar to map in real time the acoustic reflections from the body surfaces of whales as they swim past the boat or as we can manoeuvre the boat into a position to observe their habits such as feeding.  Ultimately, if we can obtain consistent and representative measures of body dimensions then SMRU might be able to observe aspects of body condition change during a season.

The sonar we are working with is the latest 3D sonar from CodaOctopus the Echoscope.  This sonar sends out a broad spectrum of acoustic energy about two, main frequencies, namely 375kHz and 610kHz.  The energy is recorded on an array in 3D that allows the reflected signal to be correctly positioned within a cone of insonification that is about 50degree in width and height.  With the addition of positioning and motion reference to the sonar, together with an insonification rate of up to 10 pings per second it should be possible to track the whales in real time.  What we are up here determining is if we can not only track them and thus ascertain their behavioural characteristics but if the sonar will also give us the resolution to be able to make precise body measurements.  This will require quite a bit of processing to first remove any noise in the data such as the fish schools that the whales are often hunting, the clutter from wave action at the surface and the seafloor.

SMRU boat Tango with Echocope fitted to starboard

So here we are in Grundarfjordur, on the Snefels peninsular with the team (Filipa Samarra, Sara Tauares, Miguel Neves, Fedutin Ivan, Olga Filatora, Sebastien Houillier, Paul Wensveen, Kagari Aoki, Julie Becsau, Jose Guilabert, Melanie Chocholek and Luke O’Connor) that will also be making a record of photo ID, sound recordings, tagging whales with motion sensors and taking samples for biopsy.  Why Grudarfjordur? Well over the last few years there have been large number of orca that visit the fjords in winter to feed on the vast stocks of herring that congregate in the still, cold and somewhat protected waters. 

The setting is spectacular with snow-capped mountains of layered basalts surrounding the fjord. Sure, its cold with frozen ground and even the snow at sealevel with an icy crust but that does not seem to daunt the Icelandic horses with their heads bowed to the constant north-easterly winds. 

Our mornings start with a check for orca in the fjord.  If there, and this is usually given away by the flocks of gulls and the odd eagle that flock above the feeding whales, then we launch the boat.  The sonar is deployed after making observations of behaviour in order that we can determine if the sonar is having a detrimental effect on the orca and then it’s a gentle approach to groups where they are feeding in order to obtain data.  On a good day we will get sonar data, photo ID of the whales and if lucky some biopsy samples. 

Image from Echoscope showing large male orca and young orca in background

Processing is going to take some weeks to obtain quantitative information but at the end of the trip we have managed to record some great data showing behaviour including groups working the herring schools up to the surface for feeding.

There is a great team here and it’s a real privilege to work on this project and in this part of the world – well worth a visit if you are interested in whales, outdoor scenery or of course for views of the northern lights!  Next time I must remember to bring my ice climbing and skiing gear for those days that the whales do not turn up!

Kilwa Marine Geophysics Survey, 2014

I have just returned from Tanzania working with Dr Ted Pollard from the British Institute in Eastern Africa and Elgidius Ichumbaki from the University of Dar es Salaam. Ted (also an honorary researcher at St Andrews) has been researching coastal archaeological sites along the southern Tanzanian islands near World Heritage site of Kilwa for over 10years.  His studies have documented settlements and trade back to Middle Stone Age with extensive developments from the 14C and 15C based on gold trade  that originated in modern Zimbabwe. To date, most of his work has been focused around recording intertidal sites in relation to the changing geomorphology that will have dictated the land use.  He has shown how river channels and harbours have silted up, settlements abandoned both as a result of nature and from human pressure.  There is a fascinating story in this coast line and one that despite the obvious immediate differences (its hot and the water is warm) has many similarities to the work that many of us are conducting around the North Sea.  

Kilwa Fort, Kilwa World Heritage Site, Tanzania

So this year Ted wanted to investigate the sub-tidal part of the study area.  In order to do this I have brought out our SwathPlus 468kHz bathymetric sidescan.  This is the sonar that we have been using up in Orkney, Scotland (see earlier posts) to successfully map the submerged topography (the drowned landscape) but also using to map different types of biological habitat on the seafloor.  It was deployed with a TSS DMS205 motion reference unit, sound velocity probe, Vector Hemisphere GPS and Topcon RTK dGPS.  Unfortunately here I do not have the advantage of bringing a custom survey vessel so we are relying on the collaboration with the Tanzanian Antiquities Department.  Check the video clip to see how the survey went and get a feel for the place. The boat required a fair amount of impromptu rigging and a couple of visits to a local woodworking shop - here my demands on yokes to go around the keel of a boat were a welcome change from making bed frames I think.

Charles Okeny from BIEA surveying using the SwathPlus bathymetric sonar

Over the course of the two weeks we managed to get a fair amount of the inner harbours covered including some great detail around the old fort and palace. Water depths ranged down to 65m and from the mapping it appears that there are a number of submerged coral terraces plus some great sediment features. 

As with any geophysics, it is only as good as the ground truth and so there was nothing for it here but to jump into the water to get some.  Whereas I am usually a fan of putting down an ROV (remotely operated camera) there was just not the facilities to do this and so we hired kit from a local dive centre and had to do the honourable thing – diving around coral reefs can be a hardship, honest!

The final map of bathymetry showing a deep (>60m) channel with steep coral shelf breaks

Dr Ted Pollard 

The result of the day of targeted dives proved out many of the sonar targets and gave some valuable information on seafloor type.  It also gave us the first confirmation of archaeological significance with a large pottery scatter at one site.  Ted will now be following this up with careful analysis/identification of the pottery.