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Land of Fire: 23 Degrees Team heads to Tierra del Fuego

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Stephen Marsh Stephen Marsh | 18:30 UK time, Friday, 4 February 2011

d ~ 90'048'000 km: day 35 of Earth's orbit

Kate Humble and the 23 Degrees team have travelled down to Puerto Williams, a town sometimes called the southernmost city in the world. It's located in Tierra del Fuego at the very southernmost tip of South America.

The 23 Degrees team are embarking on an epic journey down to the Southern Ocean on a 66 foot ketch called the Santa Maria Australia. They are sailing south west down the Beagle Channel, following in the footsteps of Charles Darwin who travelled this route 179 years ago on the HMS Beagle.

The team's mission is to discover what powers the weather in Tierra del Fuego and in the southern hemisphere.

They get their first clue a few kilometres down the Beagle Channel, when they come across a rather unexpected sight, a large glacier. The reason it's unexpected is that the Beagle Channel is on the same altitude south [55 south] as the Lake District in Britain. And even though the Lake District is hilly you don't see too many glaciers there. It's even stranger when you realise that it's summer in the southern hemisphere at the moment and glaciers are really sensitive to summer heat. The hotter the summer the more likely the ice is to melt, and the glaciers to retreat.

What makes it even more intriguing is that Perihelion happened just a month ago. Perihelion is the point on our orbit around the sun when the planet is closest to the sun. During Perihelion the planet gets 7% more sunlight than when it's furthest away during July. Also at this time of the year the southern hemisphere is tilted towards the sun, so in theory it should be hotter. But it's not or the glaciers would melt away. Summers in the southern hemisphere are actually cool; in fact they are actually cooler than summers in the northern hemisphere.

To discover why Kate and the team are sailing through the Beagle Channel to the open sea of the Southern Ocean on the way she hopes to see a miniature forest with trees that are only a metre tall. These gnarled stumpy trees are caused by the incredible winds that blow across the land 24/7.

Once they get out on the open sea she'll see first hand what's controlling the climate. They are surrounded by seas; to the west is the Pacific, to the east the Atlantic, and the south the Southern Ocean. The only land around here is the narrow strip of Tierra del Fuego. But there's very little land across the rest of southern hemisphere, it's mainly ocean and that's the key to the climate. It's all about the difference between how land and water react to heat. Land reacts fast and warms and cools rapidly, so where there are large landmasses it gets very cold in winter and hot in summer.

The oceans react very slowly to heat so they take a long time to warm up and cool down. So they are still cold in mid-summer and warm in mid-winter. The warmer water in the oceans keeps the temperatures of the air warmer just as cold oceans will keep temperatures colder.

Because there is much more water than land in the southern hemisphere the oceans dominate the climate, so even though it's mid summer the large areas of cool oceans keep temperatures down. The cooling influence of the oceans is so powerful that it counteracts the effects of Perihelion. So even though the southern hemisphere is both closest to the sun, and tilting towards it, the power of the oceans keeps summers cooler.


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