Friday, 31 January 2014

Something’s happening to Magnetic North in Great Britain in 2014 by Susan Macmillan




The magnetic field of the Earth is changing slowly every day. This year, for the first time in 350 years in Great Britain, we’ll see the direction of magnetic north move from being west of grid north to east of grid north. Susan Macmillan of the Geomagnetism Team explains what’s happening and what’s in store for compass users in Great Britain over the next few years.



Estimates (Jan 2014) of grid magnetic
angle at mid-2014
and its annual decrease.
Magnetic north is west of grid
north by
the amount shown. Red-shaded region is

where it is EAST.
At the BGS we derive a model of the Earth’s magnetic field valid for the area of Great Britain using data collected at three magnetic observatories and a network of repeat stations. A new model is derived every year to keep accurate track of the slow changes in the Earth’s magnetic field. This model is used to calculate the angular difference between the directions of grid north and magnetic north, otherwise known as grid magnetic angle (GMA). The map shows how grid magnetic angle currently varies across the country, and also how it varies in time. 


In the bottom left corner you can see where magnetic north is east of grid north. It will take approximately 20 years for the rest of the country to see magnetic north change from being west to east of grid north. The last time magnetic north was easterly in the UK was over 350 years ago in about 1660 when it was recorded by more than one observer in and around London. Since then we have had varying grid magnetic angle with the maximum being about 27° west in Shetland in 1818. 


You can calculate grid magnetic angle by going to the BGS Geomagnetism website and using the GMA calculator. The calculator outputs a grid magnetic angle for any given location (entered as a British National Grid reference, latitude and longitude or postcode) which you can then use with a magnetic compass and map. To learn about using a compass and map read this blog by the Ordnance Survey.



Grid magnetic angle and its estimated annual rate of change are shown on Ordnance Survey maps.  Because of the changes in 2014, the OS have had to design a new icon to show the new relationship of magnetic north compared to grid north.  


What is causing this gradual change in direction of magnetic north in the UK?
 

Now the difficult stuff. The Earth’s magnetic field is sustained by a dynamo process in the liquid outer core of the Earth. Interactions between the flow of the molten iron-rich material in this region and the magnetic field generate electrical current that, in turn, creates new magnetic energy which sustains the field. Energy sources for the fluid motions are primarily convection - as the Earth slowly cools down, warmer fluid rises and cooler fluid falls and solidifies onto the inner core. This in turn changes the chemical composition of the fluid, and buoyancy forces result. The rotation of the planet also contributes. This dynamo process also results in the movement of the magnetic north pole but because the Earth’s magnetic field is more complicated than dipolar magnetic compasses do not point directly to the magnetic north pole. Compass needles instead align themselves with the local magnetic field.


What does this mean for compass users in Great Britain?


This change will affect ramblers and hill-walkers who use grid magnetic angle to correct between magnetic bearings and grid bearings. A common mnemonic to help remember whether to add or subtract the correction, “grid to mag, add – mag to grid, get rid”, will unfortunately become redundant when magnetic north becomes east of grid north. Up till now a westerly grid magnetic angle is added to a grid bearing to convert it to a magnetic bearing, but from 2014 and onwards whenever you see an easterly grid magnetic angle in the margin of the map you need to subtract the angle from the grid bearing.

A mnemonic that will work after the change is “East is least, west is best”. This mnemonic is applicable anywhere in the world, no matter whether magnetic north is west or east of grid north. The other nice thing about this mnemonic is that it is also applicable with any type of map with north lines. The north lines can be either grid north lines or true north lines as on mariners’ charts. “Least” in this context means “subtract” and “best” means “add”.


However this mnemonic only works if you are converting from map to magnetic bearings. This is the most common use but if you are applying it when locating yourself on a map by two intersecting magnetic bearings to nearby identifiable features, you have to remember this because in this case you are converting from magnetic to map bearings. 


Susan Macmillan

If you can come up with a better mnemonic that is applicable for all circumstances Susan Macmillan would like to hear from you!






Monday, 20 January 2014

Sun, Sand and Sabkhas by Clive Mitchell

Me [BGS Industrial Minerals Specialist
Clive Mitchell] sampling dune sand
The BGS have worked in the United Arab Emirates (UAE) for over 10 years, in which time we have produced new geological maps for the whole country and also studied the mineral resources, urban geology and geohazards. The UAE is only the second country in the world to have fully contiguous digital geological map coverage (the first country was the UK and the BGS did both!). For my part I have lead several projects on the limestone and dimension stone resources. All of the maps and reports are available from the UAE Ministry of Energy which is based in Abu Dhabi.
Burj Khalifa framed by the Emirates
Towers, Dubai

I recently spent 10 days in the UAE to undertake some fieldwork and silica sand sampling for a glass company. Just before this I took part in the MENA Mining conference in Dubai. MENA is the Middle East and North Africa region. Reading the opening address from H.E. Dr Matar Al Neyadi, Undersecretary at the Ministry of Energy, I was surprised to learn that this region covers an area of over 11 million km2 and has a population of 317 million (larger than Europe with less than half the population). MENA is not well known for its mineral production with little in the way of metal production. It is relatively well known for its production of industrial minerals such as phosphate, gypsum and potash. What I found encouraging was the presence of representatives from Egypt, Libya and Iraq, all there to promote their natural resources and reiterate that their countries are ‘open for business’. 


BGS Geologist Andy Farrant
After four days in Dubai it was definitely time to get out of Dodge and head off west to the desert. I was working with my BGS colleague, Andy Farrant, an experienced mapping geologist who lead the work to map the western part of the UAE. Read about our work on the BGS Geological mapping in the United Arab Emirates pages. Our base was the charming Dhafra Beach Hotel in Jebel Dhanna (about 350km west of Dubai) complete with air con (vital), dehumidifier (even more vital!) and a friendly lizard. Incidentally, yes there is a beach by the hotel but its attraction is diminished somewhat by the presence of the nearby oil refinery at Ruwais. 

Zeugen - dune sandstone with gypcrete cap rock
Our mission was to find silica sand suitable for glass production (no further details I’m afraid as this was a commercial job). Suffice it to say we visited lots of localities with promising looking quartz-rich sandstone and sand deposits.

It was great to get out of the office and back to real geology for a change. Dusted off my hand lens, GPS and sampling gear. Along the way I was introduced to some of the UAE’s hidden gems. Such as the Zeugens standing proud over the Sabkhas, fossil bone beds stuffed full of bones, oyster shell and turtle carapace, and the 8 million year old elephant tracks in Miocene limestone pavement. Wow! 

8 million year old elephant tracks in
Miocene limestone pavement
One strong feature, apart from sand dunes, is the presence of Sabkhas. These are found everywhere where water has interacted with the surface. Salt is dissolved from the ground, brought to the surface by the intense evaporation and deposited as large crystals which disrupt the surface forming a strange buckled landscape.

Back to the sand! Dunes are everywhere getting progressively more quartz rich and larger as we worked our way south away from the coast. Modern dunes overlay quaternary palaeodunes which in turn overlay Miocene palaeodunes. All formed from the same sand worked and reworked from that blown inland from the Arabian Gulf when the sea levels were lower or deflated from older Miocene rocks. Ultimately the quartz sand came from the mountainous highlands of Saudi Arabia where rivers brought it down into the Arabian Gulf around 8 million years ago.

'Camel Jam' on the road to the Liwa, Al Gharbia, UAE
How could I forget the camels?! These are the pride and joy of the local Emiratis who jealously guard them from vantage points in their 4x4s. I would imagine moving your camels over sand dunes would be very slow. Hence we were treated to frequent ‘Camel Jams’ on the roads.

One blessed relief, the desert is too dry for most insects and we were free of these usual field work pests!


Whoever said desert geology is boring, surely it’s all just sand isn’t it? Well, there is plenty of exposure in the interdune areas which are surprisingly free of modern dune sand. In addition, in the same way that Eskimos are claimed to have over 100 words for snow, the BGS have managed a dozen for sand! Aeolian sand, low dunes, sand sheet, ribbed sand sheet, dune ridge, Barchan dunes, Mega-Barchan dunes, Zibars dunes, palaeo dunes (carbonate- or quartz-rich), star dunes and beach ridge deposits (I’ve probably missed some out!).


Etihad Rail line, Al Gharbia, UAE
One last note, this region of the UAE is currently witnessing the rapid construction of a very large infrastructure project. Etihad Rail is putting in place a rail line that will not only link all the major cities in the UAE, it will also link the UAE with Bahrain, Kuwait, Qatar, Oman and Saudi Arabia (Gulf News 29 October 2013). It is incredible to learn that this network will be completed by 2018!

Clive Mitchell
Twitter@CliveBGS

Wednesday, 15 January 2014

The Quaternary Research Associations 50th Anniversary Conference by Prof Melanie Leng

The audience at the QRA’s Quaternary Revolutions
meeting (@Tim Lane)
The new year traditionally brings with it not only resolutions, gym memberships and fad diets but for our scientists a round of exciting geological conferences! This year the Annual Discussion Meeting of the Quaternary Research Association (QRA) was held at the Royal Geographical Society in London and was themed around Quaternary Revolutions. Here Melanie Leng tells us about the meeting attended by scientists from far and wide…

The Quaternary Revolutions meeting was organised to celebrate the 50th anniversary of the QRA. The QRA was formed in 1964 and over the years has developed into a research group which investigates and debates the Earth system and its relationship with past and future human development and society.


BGS’s Andrew Finlayson was awarded the Lewis
Penny Medal for his research on Scottish
glaciations at the QRA meeting (@Tim Lane)
There was an excellent series of speakers who discussed ten themes covering the full range of Quaternary science. The talks reviewed the major scientific revolutions in their particular themes over the last 50 years and then the audience was invited to debate the forward look and future developments. It was a fitting way to celebrate the QRA’s 50th anniversary as well as a stimulating science conference.

 Of particular note were talks by Chronis Tzedakis (UCL) on causes of climate change, Chris Bronk-Ramsay (Oxford) on measuring time, Maureen Raymo (Columbia) on ocean records, Mary Edwards (Southampton) on advances in palaeoecology and Chris Stringer (NHM) on human origins, environments and impacts. The full range of talks are listed in the programme.


BGS BUFI student Jack Lacey from University of Leicester
presenting his PhD research on climate change in the
Balkans at the QRA meeting
Many thanks to the organising committee headed by the outgoing president (Dan Charman, Exeter). The meeting was extensively tweeted (thanks mainly to our early career scientists), for updates check out #QRA50 or follow @QRA50.

Mel

Friday, 10 January 2014

The geomagnetic storm that wasn’t.... by Dr Gemma Kelly

You may have been aware in the last few days of a lot of media excitement about a chance to see the Northern lights here in the UK. So, last night many people in the country (space weather experts included) were glued to computer screens, and in some cases the night sky itself, in anticipation of the aurora arriving....but then it never materialised!
So why all the fuss? Well, let’s start at the beginning...


An image of the Sun from the Solar dynamic
observatory during the X-class flare (the bright
area near the centre) on 7th Jan.
On 7th January at around 18.30 there was an X1-class (moderately strong) solar flare close to the centre of the Sun. However, a flare by itself is not enough to cause an aurora here on Earth. Associated with this flare was a Coronal Mass Ejection (CME), which is a massive burst of charged gas and jumbled up solar magnetic field. In this case the CME appeared to be directed almost straight at the Earth and initial estimates of the speed it was travelling were high (around 2000 km per second). 

Given all that information most forecasters (including us here at the BGS) were in agreement that this CME was very likely to hit the Earth’s magnetic field at some point on the 9th January. When a CME arrives at Earth we expect to see a shock signature observed in the ACE satellite data. This means we see a sharp jump in the velocity and magnetic field of the solar wind – which is a continuous stream of charged particles released from the Sun. 


Sure enough, just after 19.00 on the 9th the shock arrived, so the CME had arrived – time to get excited (and tweeting). However, to get a geomagnetic storm, and therefore the Northern lights there are a few more complications....


Firstly, the CME had arrived several hours later than expected suggesting it was a bit slower than first predicted - in general the faster the CME the bigger the resulting geomagnetic storm. Secondly, the shock was also quite small which might mean that we only received a glancing blow from the CME, and most of it missed us. Thirdly, and most importantly, to get a geomagnetic storm a CME really needs to cause the interplanetary magnetic field (the field trapped in the solar wind – or IMF) to turn southwards, which allows much more energy into the Earth’s magnetic field. Following last night’s CME arrival the IMF stayed stubbornly northwards, therefore, the geomagnetic storm never really got going.


In short, space weather forecasting is really hard! We are continuously improving the way we forecast and model space weather, but until we can get more information about the CMEs before they reach us there will always be a lot of uncertainty.


To get daily space weather forecasts follow @BGSspaceWeather and for those all important aurora alerts follow @BGSauroraAlert.

Gemma @GeomagGem

Extra bits

Flares are caused by the explosive reorganisation of magnetic fields in the Sun’s atmosphere, and are classified according to how powerful they are as A (the least powerful), B, C, M or X (the biggest). X-class flares are the most powerful, ranging from X1 up to at least X28, where an X10 is 10 times more powerful than an X1.
‘Space weather’ is a term to describe the conditions in the space between the Sun and the Earth. Changes in space weather are almost exclusively driven by events on the surface of the Sun, and the Sun’s atmosphere. 


To find out more on the science of geomagnetism go to our website here.

Thursday, 9 January 2014

Using “proxy” data to tell us about past climate change by Melanie Leng

One of the highlights of 2013 was publication of our research, in collaboration with the British Antarctic Survey and various UK Universities, on past climates along the Antarctic Peninsula, here Professor Melanie Leng tells us how climate change from 11,000 years ago to the last few decades has affected the Antarctic from 'proxy data'

Prof Melanie Leng with Dr Robert Mulvany
(British Antarctic Survey) examining ice from the Antarctic Peninsula
The Earth’s climate is always changing and shifts can be very dramatic especially during glacial (large Antarctic and Northern Hemisphere ice caps) and interglacial (smaller ice caps) periods. There is debate as to what causes the change between “icehouse” and “greenhouse” conditions, but the change is usually quite slow taking hundreds to thousands of years to wax and wane between the two conditions. At the moment we are experiencing probably one of the highest rates of change of CO2 concentrations in the atmosphere and as a result parts of the globe are experiencing warmer or more unpredictable climate than we have known for the past 150 years.  For example the Antarctic Peninsula is experiencing one of the highest rates of warming (3°C in the last 100 years) than anywhere on the Planet and freshwater from the melting of the Antarctic ice sheet is entering the ocean at unprecedented rates, ice shelves are collapsing and glaciers are retreating - all quite scary information when it has been calculated that the Antarctic ice sheet alone holds the equivalent of 70m of global sea-level rise. The Antarctic continent is in a key position to be influenced by global climate change being impacted by both global ocean and atmospheric circulation, and therefore a go “thermometer” for monitoring present and predicting future change. One question that faces us is what is causing the current high rates of melting? Current thoughts include increasing greenhouse gases and ozone depletion due to man’s activities but also changes due to natural cycles of climate variability in the South Westerly winds and ocean temperatures in the equatorial Pacific.  The key to unpicking natural from man made processes are comparing current changes (with our increasing concentrations of CO2 in the atmosphere) with past natural climate variability.
The Antarctic Peninsula is experiencing
one of the highest rates of warming on the
Planet over the last century

There are several ways to get evidence on past climates around the Antarctic continent, we can look at the amount of freshwater (from melting of the ice) entering the coastal environment from the chemistry of algae that live in the coastal zone, we can obtain past temperatures from the chemistry of coastal ice caps, and we can calculate  temperatures and CO2 changes preserved in small pioneering plants that are found in pockets around Antarctica. Here at the British Geological Survey we have used all these methods to obtain climate “proxies” back through time for the Antarctic Peninsula.


Mosses from the Antarctic Peninsula are being
used to look at modern climate change and
how it is affecting plant communities
What we are discovering from our research is that melting of the Antarctic ice cap has been very variable over the last 11,000 years since the ice cap retreated onto land as the world shifted from icehouse (large ice caps) to greenhouse (small icecaps) conditions. Before 11,000 years ago the ice cap was thought to have been much bigger, extending over the coastal margins. From our proxy data we have shown that over the last 11,000 years there has been changes between melting and build up of ice related to different processes through time. The chemistry of the algae that lived in the coastal zone and subsequently accumulated on the sea bed have shown that sometimes high rates of melting are due to the transfer of heat through the atmosphere during periods of warmer Equatorial Pacific ocean surface temperatures(1). Temperature data calculated from the chemistry of the snow and ice show that the Antarctic Peninsula has experienced very warm summer air temperatures over the last 600 years, but that since the mid twentieth century  the level of summer melting is unprecedented in parallel with rising greenhouse gases into our atmosphere(2).  The growth rates of moss plants over the last 150 years also show the most dramatic rises since the 1960’s alongside the greatest temperature and CO2 changes that we have seen in the last 150 years (3). Together the various proxies and different expertise of the scientists involved are showing that while climate is always variable, past changes have tended to be slower than the current rate of warming and therefore we are in a period of unprecedented rates of change.

Much of our proxy data confirms what we already know, there are natural and manmade influences on climate at different scales. Our studies help provide evidence for policy makers and Governments (like the Intergovermental Panal on Climate Change) but to you and I it helps demonstrate how fragile our planet is and how humanity is likely to profoundly transform the Earth in ways that we can only imagine by looking at proxy data from the geological archives.


Mel @MelJLeng

Prof Melanie Leng is an isotope geochemist and palaeoclimatologist at the BGS. This research is in collaboration with many scientists in the UK including colleagues at the British Antarctic Survey, and the Universities of Cambridge, Exeter, and Cardiff.

 (1) Pike, J., Swann, G.A.E., Leng, M.J., Snelling, A. 2013. Glacial discharge along the west Antarctic Peninsula during the Holocene. Nature Geoscience, 6, 199-202.
 (2) Abram,N.J.,  Mulvaney,R., Wolff, E.W., Triest,J., Kipfstuhl,S., Trusel,L.D., Vimeux,F., Fleet, L.  & Arrowsmith, C. 2013. Acceleration of snow melt in an Antarctic Peninsula ice core during the twentieth century. Nature Geoscience, 6, 404-411.
(3) Royles, J., Amesbury, M.J., Convey, P., Griffiths, H., Hodgson, D.A., Leng, M.J., Charman, D.J. 2013. Plants and soil microbes respond to recent warming on the Antarctic Peninsula. Current Biology, 23, 1702-1706.