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2010/02/07-21h17
Saint Helena, an austral isle
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| A minute piece of confetti in the Southern Atlantic ocean, the island of Saint Helena is famous for having provided the final
resting place for Napoleon 1st, as well as the zone of high pressure associated with it, which influences the entire climatology
of Africa and South America. Portrait of a volcanic peak which culminates at 823 metres...
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Situated at 15° 56' South and 5° 42' West, the island of Saint Helena which spans just 122 km², was discovered purely
by chance! Nearly 2,000 kilometres from the African coast and over 3,500 kilometres from Brazil, right at the very core
of the high pressure which generates calms and fickle breezes around this now British overseas territory, the rock wasn't
terribly visible on the horizon. However, during the third Portuguese expedition toward the Indies, Captain João da Nova initially
discovered the island of Ascension (1501) and then that of Saint Helena (21st May 1502) in the middle of nowhere!
Reaching
the unprotected shores of this inhabited landmass, he had a chapel and a few houses built, which were to be used as a stopover
along the trade routes between Europe and Asia. The discovery of this remote island contributed to the orientation of the
shipping lanes as the Portuguese introduced goats and planted lemon trees to the area. As such the island was used as a pit-stop
to resupply with freshwater and fresh food. Of particular importance in the victualling were the citrus fruits which, thanks
to their concentration of Vitamin C, enabled the risk of scurvy to be reduced, an illness which decimated the crews on these
long haul voyages.
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Remote land, an island of exileIn 1588, Sir Thomas Cavendish was the first British citizen to set foot on the island during his first circumnavigation of
the globe, the third of its kind after that of Fernando Magellan (1519-1522) and that of Francis Drake (1577-1580). Aboard
Desire, this mercenary and privateer followed in the wake of his predecessor by burning down three towns built by the Spanish
and capturing thirteen ships laden with gold on behalf of Elizabeth, Queen of England. The discovery of Saint Helena by the
English enabled her Majesty's fleet to stop off there to attack the Portuguese caravels on their way back from the Indies...
In 1592, King Philippe II of Spain was to order his fleet, sailing from Goa, to avoid making the detour to Saint Helena, which
left the slate clean for the Dutch to take possession of the island in 1633. However, given that they didn't really colonise
the island, they finally abandoned it in favour of Cape Town in South Africa.
The English East India Company decided
to fortify the area and disembarked a number of cultivators there in 1657 under the governance of Richard Cromwell. Following
that, Captain John Dutton's fleet modified the fortifications which, during the restoration of the monarchy in 1660, took
the name of James Fort, whilst the neighbouring town was given the name of Jamestown. This strategic point became the site
of several battles since the Dutch East India Company took possession of it in the Christmas of 1672, forcing governor Beale
to make for Brazil to escape. The latter took back control in May 1673 and installed a garrison of 250 soldiers there while
Charles II declared the island of Saint Helena to be "part of England, in the same way as East Greenwich is included
in the County of Kent!" Not being situated on the "tradewind expressway", this volcanic rock ended up being rather
neglected and, in addition to this, was terribly ravaged by the goats which devastated the forests and arable land...
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The end of an empire
The island of Saint Helena became famous when, after his defeat at Waterloo on 18th June 1815, Napoleon was exiled there
by the British. The emperor, who had managed to escape the island of Elba, could no longer be in contact with his supporters,
especially as the British were to claim the `neighbouring' island of Ascension at this time, in order to put together a naval
garrison there... Taking his last breath on 5th May 1821 in his final resting place of Longwood House, in what are still mysterious
circumstances since the possibility of poisoning still lingers, Bonaparte was buried on 9th May in the Valley of the Tomb
under the authority of the governor Sir Hudson Lowe. King Louis-Philippe secured the return of the ashes which were sent back
home to France and kept at the Invalides. In 1858 Napoleon III acquired the final resting place and the Valley of the Tomb
of his ancestor, which have since been managed by the French Ministry of Foreign Affairs.
King Zoulou Dinuzulu
kaCetshwayo was to succeed the Emperor by being exiled there for seven years from 1890. Following on from that, during the
second Boer war (1899-1902), the British army transformed the island into a detention centre where over 5,000 prisoners were
deported. Without any proper sheltered port, the 3,800 inhabitants were still very isolated with a single British vessel,
RMS St Helena to provide the regular link with the port of Cape Town for mail and supplies. An airport is currently under
construction there nevertheless and it is set to open in 2010.
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 The counterpart to the AzoresHowever, in meteorological terms, Saint Helena is as renowned in the Southern hemisphere as the Azores is in the North Atlantic!
Indeed year round, this austral isle and this northern archipelago are associated with anticyclones, which are relatively
stable centres of activity involving high pressure. Situated in the inter-tropical zone, their positions vary relatively
little from season to season, but they fluctuate with each day that passes according to the passage of depressions which push
them along, compress them, shift them about and occasionally split them in two... However, the Azores High is more `volatile'
than its austral counterpart Saint Helena, which is due to the configuration of the terrestrial landmass which surrounds them,
as well as the size of the ice cap covering the North and South poles.
Indeed, the differences in pressure are due
to the thermal contrast, which marks the polar cold and the equatorial heat. As the Earth rotates around itself, it drags
along its adjacent atmosphere and this movement, under the influence of the Coriolis force (diverting of a mass moving towards
the right in the Northern hemisphere, and towards the left in the Southern hemisphere), causes a mixing of the hot and cold
air masses. This helps to smooth the global temperature thanks to these thermal exchanges between the depressions and the
anticyclones.
In this way, the Saint Helena High generates a tradewind system which rotates anticlockwise from
this volcanic island which roughly marks its centre. The S'ly air flow along the coast of Africa (Namibia, Angola) turns
towards the SE in the Gulf of Guinea and beneath the Doldrums, before rotating round to the E near Brazil, the NW level with
the island of Trinidad and ultimately W in the Roaring Forties! This massive circulation thus forces the sailors coming from
Europe bound for the Indies (or setting off around the world), to go right around the Western limit of this zone of high pressure,
so as not to get caught up in the calm zones which reign at its centre.
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