Archive for the ‘Popular Science’ Category

As well as the CTD work I’m involved in and the WAGES work with buoys and balloons there is one other science team on board. They are from the National Oceanography Centre Liverpool, linked with Southampton. They are here to deploy and recover bottom pressure recorders. These are dropped over the side of the ship and sink to the bottom. They sit on the bottom for a year or more gathering data. When we come along to collect them an acoustic signal is sent out to ‘wake up’ the bottom pressure recorder, allowing the bottom pressure recorder to ‘talk’ to the ship. Then a signal is sent to make the bottom pressure recorder release from the bottom, by leaving a heavy frame behind, and float up to the surface. The bottom pressure recorder is then recovered back on board. As the instrument has been on the sea bed for at least a year some of the local wildlife is often brought back up with it! As you can expect, being brought up to the surface from around 1000 m depth is not a good idea.
Here are some of the specimins we found:

As I’m not biologically inclined I won’t many any attempts to identify them!

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20 minutes on a train, 50 minutes on a bus, 6 hours in air terminals, 16 hours on an aeroplane, and 2 new passport stamps later I have made it to the Falkland Islands! So far it looks like the Welsh mountains or Scottish highlands with a few sheep and low level vegetation, but with far less evidence of humans. The roads are a mixture of solid and loose stones, no road markings, many cattle grids, occasional signs. The buildings generally have colourful, corrugated roofs; the vehicles are mostly 4×4’s. It’s cold. Ski jacket, gloves and hat cold – I hadn’t expected that so soon.

Whilst flying over the South Atlantic watching the layers of clouds between me and the ocean and trying to do some atmospheric physics revision, I started thinking about the air right outside the window. Television screens updated us on the flight conditions – including speed, height and local time. The air outside the window was a chilly -56°C.

What would happen if a parcel of air was brought inside? This high up (10972 m or 36000 feet according to the television screens) the pressure is much lower than at the Earth’s surface, so presuming the pressure inside the aircraft cabin is the Earth’s surface pressure, the pressure of the air parcel would increase.

When pressure is increased the temperature goes up – think what happens when you use a bike pump, the valve gets hot due to the pressure of the air being forced into the tyre.

So how much warmer would the air get? Potential temperature can be used to calculate this, it is the temperature a parcel would become if brought (at constant entropy, or energy state) to a reference pressure.

Potential temperature = T(Po/P)^(R/Cp)

Where T=temperature (in Kelvin), P0 = reference temperature, P=initial pressure, R= 287 Jkg-1K-1 (specific gas constant) and cp= 1004 Jkg-1K-1 (specific heat at constant pressure).

I knew T=-56 °C or 217 K, the aircraft height was 10972 m, which (from the US standard atmosphere look-up chart) corresponds to ~225 Pascals. The reference pressure inside the aircraft cabin is assumed to be surface pressure, ~1000 Pascals.

Substituting these values into the equation to calculate potential temperature:

Pot. T = 217 x (1000/225)^(R/Cp) = 332K or 59°C

So, rather oddly, the air outside the window would become uncomfortably hot if brought inside. Luckily this can only ever be a theoretical calculation, the cabin is pressurised, and so switching the air is not possible!

The same principles can be applied to the ocean, just in reverse. Water at depth is at a greater pressure than water at the surface due to the mass of water above it. If a water parcel could be brought to the surface at constant entropy it would lose temperature as its pressure would be decreased.

(Quick Disclaimer – these calculations have not been confirmed by a grown-up scientist… I think they are correct!)

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I Like Snow.

Waking up to a world painted white after the first night I stayed in Durham may have influenced my decision to move there for three years. The discovery that Durham is very hilly, and ice-covered pavements make walking to 9 o’clock lectures slightly more interesting, didn’t come until second year. It wasn’t until my final year that we had ‘proper’ amounts of snow; walking to the train station at the start of the Christmas holiday as the snow began and returning in January with it still on the ground.

National Oceanography Centre, Southampton, December 2010

The snow last winter was thicker than any I had ever seen in England, but even if university was closed for a few days it didn’t stop my preferred mode of transport (bicycle).  It did create mayhem at airports – causing our journey by train to Holyhead to catch a ferry to Dublin (booked months in advance) to be made chaotic with crowds of Irish young professionals trying to get home in time for Christmas.

The BBC have recently shown a programme about Britain’s cold spells, with some good bits of real science. ‘Will It Snow?‘ (currently available on iplayer) looks at why Britain sometimes experiences cold winters, whether we can predict what this year will bring and the effects of the snow on the UK economy.

Another good programme from the BBC, and a very topical one for me, is Frozen Planet. Sir David Attenborough narrates this series, covering the wildlife and science of both polar regions. The penguins at the start of episode 2 (Spring) are Adelie – the most common species around the BAS base I am visiting next month!

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