Archive for the ‘Cartography’ Category

Surveyor seals reveal secrets of Antarctic depths

November 7, 2010

Original article at  New Scientist
05 November 2010 by Kate Ravilious

Ocean explorers (Image: D. Costa)

Seals are helping to map the ocean floor around Antarctica. And they are proving their worth: they have already revealed new features on the sea bed that could help researchers explain the rapid melting of ice in recent years.

Knowing the shape of the ocean floor is important because underwater mountains and valleys help to shape ocean circulation, which influences ice cover and production at the surface.

Normally such mapping is carried out by echo sounding, whereby the depth of the sea is calculated by timing how long it takes for sound waves to travel from a ship to the sea bed and back again. But the most of the sea and ocean beds around Antarctica remain unmapped because the thick ice that covers much of the region is impassable for ships.

So Daniel Costa, a marine biologist at the University of California, Santa Cruz, glued electronic depth sensors onto the heads of 57 elephant seals and tracked their movements in the Bellingshausen Sea off the Antarctic Peninsula between 2005 and 2009.

Ideal seals

“Seals are ideal because they go places where no one else has gone, and they don’t need a battery to drive them,” says Costa.

By tracking seals in previously well-mapped regions, Costa and his colleagues showed they dived all the way to the sea floor around 30 per cent of the time.

Next they analysed the maximum depths of seal dives in unmapped regions, to trace the contours of the sea bed to the west of the Antarctic Peninsula.

“We found that the troughs that cut across the continental shelf from the deep ocean to the coast are deeper and straighter than shown on existing maps,” says Laurie Padman, an oceanographer at Earth and Space Research, a non-profit research institute in Corvallis, Oregon.

In particular, the data revealed that troughs leading towards the Wilkins ice shelf were 600 to 200 metres deeper than previously thought. Such troughs act as conduits for warm water, so the greater depth may help to explain the dramatic collapse of the ice shelf in 2008.

The researchers are planning similar work in other areas around both Antarctica and the Arctic. “It is a cheap and very powerful technique,” saysPaul Holland, an ocean modeller from the British Antarctic Survey in Cambridge, UK, who was not involved in the study.

Journal reference: Geophysical Research Letters, DOI: 10.1029/2010gl044921

Ice and Silence: Extreme Working for the British Antarctic Survey

April 19, 2010

by Paul Torode and Rich Burt – BAS 31/Mar/2010

It’s not often you get to climb inside an iceberg. Held in the vice-like grip of the surrounding sea ice, the frozen colossus facing us was split by a deep crack. The bottom of the vertical cavern had at some stage flooded with seawater and refrozen. We jumped a sinister gash of open water and climbed inside the ‘berg.

Earlier, we’d left our skidoos and field camp and had to abseil the ice cliffs to reach the sea ice: now we were inside the iceberg itself, awestruck by the azure glassy hardness and the immensity of it all. Soft powder snow adorned the entrance of the cavern, and crystals festooned the ‘roof’ high above our heads. As we descended the wondrous symmetry of the two ice walls eventually met in a hairline crack. Outside it was -40°C – our breath frosted heavily on our clothing and our crampons bit aggressively into the ice. In a matter of weeks this ‘berg would break free of the ice and drift into immeasurable seas.

I’ve seen some pretty unusual sights, working as a Field Assistant for the British Antarctic Survey (BAS). Seals swimming under the ice you’re standing on. Powder snow so deep your skidoo leaves a trench behind you. Frozen landscapes of implausible tranquillity take your breath away. I’m one of a team whose job is to support scientists going ‘deep field’ to investigate big questions like climate change. Antarctica is arguably the Earth’s greatest natural laboratory and an early warning system for global change.

BAS operates five research stations, five planes and two ships. During the short summer months life is pretty hectic for everyone. As a Field Assistant, you spend a great deal of time off-station and get to experience the continent more than most.

In summer, before going deep field, I assist the pilot to load and fuel the Twin Otter aircraft before clambering on board. I often get to sit up front as ‘co-pilot’. Watching the plane take off and leave as we set up a remote field camp is a defining moment for any Field Assistant or scientist. For two months we might work from a static camp, or travel by paired skidoo and sledge, linked together by thick rope for safety in crevassed areas. It’s a heavyweight, ‘belt-and-braces’ expedition. Once the orange pyramid tent is firmly pitched, we brew up, crack a big bar of chocolate and enjoy the most comfortable camping imaginable.

In winter days when you’re confined to the station there’s all the maintenance work on field equipment. Servicing field kit takes time in the cold, dark and windy Antarctic winter. But when weather relents there’s great enthusiasm for recreational trips that give groups a chance to have a break from station life and learn valuable field skills. It’s often these trips that the most vivid memories of the Antarctic are formed. Which brings me back to that iceberg!

Paul Torode for the British Antarctic Survey

Original article with many more beautiful pictures and more information here

Plotting Vineland: the Skálholt Map (Strange Maps weblog)

April 18, 2010

Strange Maps is a weblog specializing in strange maps. This post concerns a possibly forged map of Vinland, or North America as it is now commonly called. This informative and inspiring weblog is highly recommended.

The Vikings set foot in America just over a millennium ago, but credit for the discovery generally goes to Columbus, who only stumbled upon the New World almost 500 years later. One reason might be that the Norse involvement in North America was brief and inconsequential, whereas Columbus’ rediscovery led to the European conquest of the Americas. Another is that the Norse discoverers didn’t leave behind any maps of the lands they called Markland, Helluland and Vinland (*).

But if the Vikings didn’t map their discoveries, they did relate them in sagas. These later did form the basis for maps, the most famous of which is the Vinland Map. Reputedly a 15th-century copy of a 13th-century original, that map, now in the possession of Yale University, is likely to be a clever, relatively recent forgery (see #57 for a more thorough discussion).

The Skálholt Map, shown here, is less well known, but has the advantage of being authentic. The first version was made in 1570 by Sigurd Stefánsson, a teacher in Skálholt, then an important religious and educational centre on Iceland. Stefánsson attempted to plot the American locations mentioned in the Vinland Saga on a map of the North Atlantic. Stefánsson’s original is lost; this copy dates from 1669, and was included in description of Iceland by Biørn Jonsen of Skarsaa.

The map mixes real, fictional and rumoured geography. In its southeast corner, the map shows Irland and Britannia, and to the north of both the Orcades (Orkney Islands), Hetland (Shetland Islands), Feroe (Faroe Islands), Island (Iceland) and Frisland, a particularly persistent phantom island discussed earlier on this blog (#62).

The northeast part of the map shows the mainland of Norvegia (Norway) and to its north Biarmaland (the semi-mythical Bjarmia, possibly the area of present-day Archangelsk). On the top part of the map are situated the wholly fictional lands of Iotunheimar (Jotunheim, in Norse mythology the home of the giants) and Riseland (another land of titans), with attached to it Gronlandia (Greenland), its flowing coastline resembling the lobed margins of an oak leaf.

In the Mare Glaciale (Ice Sea) in the north is Narve Oe, possibly translatable as the Island of Narfi (the father of Nott, the night). Two place names, both on Greenland, are illegible.

Greenland is of course an island, but was considered by the Vikings to be a huge peninsula of a contiguous northern mainland, that continued to America, where are noted Helleland, Markland and Skraelingeland (after the Viking name for the natives). Marked vertically on the map’s southwestern edge is the name Promontorium Winlandiae (Promontory of Vinland).

In a development that would have pleased Stefánsson, the Skálholt Map has helped determine the actual location of a Norse site in North America. The map indicates that the northern tip of Vinland is on somewhat the same latitude as the southern coast of Ireland (app. 51°N). This encouraged the excavations at L’Anse-aux-Meadows on the northern tip of Newfoundland, which in 1960 yielded the first archaeological evidence of Viking presence in America.

This map was taken from this page at the Kongelige Bibliothek, the Danish Royal Library. The vignette, in Latin, refers to the original map by Siurdus Stephanius (Sigurd Stefánsson). The numbers on the map match the legends (A to H) next to the map, also in Latin. Can anyone provide a translation?

———-

(*) Generally translated as Flatstone Land, Wood Land and Grapevine Land, respectively.

Original article here

Interactive map of the Antarctic: browse and download recent satellite images

February 15, 2010


British Antarctic Survey

As the Antarctic field season continues with the usual mix of exciting research programmes new enhancements to the online satellite image system that improves ship safety and efficiency are launched.
The Polar View sea ice service, coordinated by the British Antarctic Survey, has greatly improved the service for the 2009/2010 Antarctic season. A combination of easier access through the new website and a significant increase in the number of images available means more real time sea ice information. The range of users of this service continues to expand, encompassing everything from science vessels to tour ships to those coordinating rescue efforts.

The new website (www.polarview.aq) now provides an interactive map displaying the latest imagery and sea ice information. Simple tools allow users to zoom into their area of interest and see recent cloud free satellite imagery from the European Space Agency. In combination with other information provided by partners in Denmark and Germany, anyone can access an up to date picture of current sea ice conditions, even on ships with limited internet access.

Thanks to the frequent satellite images being acquired for the European MyOcean project, users of the Polar View service benefit from refreshed sea ice information at least every three days. Keep an eye on the website for updates about new services in the pipeline. As well as easier access to sea ice drift information and iceberg locations, the Norwegian Meteorological Institute will shortly begin delivery of interpreted ice charts. All of which make for a more comprehensive sea ice service.

http://www.antarctica.ac.uk/by British Antarctic Survey   5:26 AM Wed 10 Feb 2010 GMT

Original article here

Olaus Magnus Carta Marina (1539)

January 18, 2010

This beautiful map of Scandinavia and Northern Europe was a landmark (literally) effort with a high level of correctness and realism for it’s time, although creatures and people shown are both real and fanciful. I particularly enjoyed seeing lapplanders riding reindeer into battle, moose charging attacking wolves, a bear (?) defecating in the woods, a man playing a huge fiddle in his lap to arctic swans and a pair of fish in northern Iceland, a woman milking a reindeer near Umeå, The Saltstraumen maelstrom in northern Norway, the appearance of important driftwood outside of Greenland as well as tall trees growing on Greenlands east coast.
Jonas/Hornorkesteret

The Carta marina (Latin “map of the sea” or “sea map”[1]), created by Olaus Magnus in the 16th century, is the earliest map of the Nordic countries that gives details and placenames. Only two earlier maps of Scandinavia are known, those of Jacob Ziegler and Claudius Clavus.

Wikipedia article here