Sunday, November 5, 2017

Mapping the seafloor


Having detailed knowledge of the shape of the seafloor is essential for generating nautical charts for navigation.
It is also needed for exploration, fishing, coastal management and for understanding ocean currents that transport heat, nutrients and pollutants.
While mapping the seafloor was traditionally carried out using sonar on ships, optical satellite data provide global, high-resolution maps that show ridges, valleys and sediments.
-courtesy of ESA-

Saturday, November 4, 2017

Tinkerbelle : Manry's dream

Robert Manry was not a silly dreamer: in 1965, he sail across the Atlantic in a 25 foot sloop
He sailed his tiny sloop, Tinkerbelle, from Falmouth, Massachusetts to Falmouth, England.
Crowds turn out to cheer Robert Manry as he completes his lone crossing of the Atlantic. 

From DuckWorkMag by Bryan Lowe

It was a different time when Robert Manry set out to cross the Atlantic in a 13.5 foot boat.
In 1965 the world seemed consumed by Vietnam.
Manry was just another young father trying to raise a family and earn a living.
He was a copy editor of a good size newspaper.
He had no expectation of fame or financial reward. Even the idea of writing a book seemed no more than a secondary thought.
His goal didn't even seem clear to him.
He had bought a small boat to go on day trips with his family.

Like many of us, he seemed to enjoy working on the boat even more.
He took the modest little day sailer and added a small cabin, cleaned it up, and added some paint.
Seemingly out of the blue a friend asks Manry if he wants to sail across the Atlantic with him in a 25 foot sloop.
The offer was made mostly in jest, but it wasn't seen that way by Manry.
Although it seemed outside his nature, it had been a dream of his for almost 30 years.
Manry immediatly set to work on making the dream come true.
He was even granted time off from work.
His friends thought him a bit daft, but for some reason the idea seemed plausible to many.
Some even said they wished the could go along.

As Robert rolls along through heavy weather, people who knew him describe his voyage...

But within weeks he was alone.
His trip had fallen through and his crowd of would be sailors suddenly had others things to do.
For Manry the dream had gone too far.
Or perhaps he thought of some of his neighbors who had thought him a silly dreamer.
He still wanted to go.
He knew it would be an adventure, but it is clear he had no idea what he faced.
Without telling anyone but his wife and children he set about making plans to take their little family sailboat across the Atlantic alone.

The boat was a poor choice for his mission.
In addition to being too small, it's entire design was for a pleasant afternoon on the lake.
Even with his modest cabin addition, the boat had no business on open waters.
The hull wasn't deep enough... or wide enough... or strong enough.
The cockpit was almost an open shelf offering little protection from the wind or the waves.
There really wasn't enough room for provisions for the long journey ahead.
His ignorance created calm, if not exactly bliss.


This is a rough cut trailer for the documentary film. 

During his voyage he was remarkably lucky.
What I find so enjoyable about this book is not the blatant bravery or the remarkable hardships.
It is Manry's simple old fashioned charm and enthusiasm.
You get the feeling of sitting in his living room, his wife bringing snacks on the TV tray while the kids watch the latest episode of My Three Sons across the room.
There is no bravado.
His world is filled with people who want the best for him, and he wishes the best for them.
Nature is not put on a pedestal, nor is there a battle of man versus nature.
It's just a bloody nice trip.
Sure his rudder broke... yes there were some 20 foot seas... and yes he did get knocked overboard a few times.
But they seem mere footnotes to his constant enthusiasm and belief that he will make it.
There is no sex.
There are no fights.
There is no doubt.
Manry makes it, and we are there cheering for him as he pulls into harbor surrounded by the press of the World and thousands of well wishers.
The reception a total shock to Manry.
The book is something of a window into the past. It's writing style more akin to the Wind in the Willows than The Perfect Storm.
As I finished the book I wished Manry was still alive for I had many questions.
He seemed such an unlikely person to sail a boat across an ocean.
He didn't have that driving wanderlust or fear of commitment that seems to drive so many others.
What did he do next?
Was this the first in a series of adventures, or did he settle down to a life of family and work?
Why did he do it?

Friday, November 3, 2017

New Greenland maps show more glaciers at risk

UCI’s BedMachine ice mapping technique enabled the creation of a three-dimensional image of a portion of the northwest coast of Greenland.
Ocean bathymetry is shown in blue and ice surface topography are displayed in white and orange.
Mathieu Morlighem / UCI

From UCI

UCI-created high-resolution charts will inform future ice and sea level forecasts

New maps of Greenland’s coastal seafloor and bedrock beneath its massive ice sheet show that two to four times as many coastal glaciers are at risk of accelerated melting as had previously been thought.

Researchers at the University of California, Irvine, NASA and 30 other institutions have published the most comprehensive, accurate and high-resolution relief maps ever made of Greenland’s bedrock and coastal seafloor.
Among the many data sources incorporated into the new maps is data from NASA’s Ocean Melting Greenland campaign.

Lead author Mathieu Morlighem of UCI had demonstrated in an earlier study that data from OMG’s survey of the shape and depth, or bathymetry, of the seafloor in Greenland’s fjords improved scientists’ understanding of both the coastline and the inland bedrock beneath glaciers that flow into the ocean.
That’s because the bathymetry at a glacier’s front limits the possibilities for the shape of bedrock farther upstream.

(a) Data coverage, including ice-penetrating radar measurements (Center for Remote Sensing of Ice Sheets, High CApability Radar Sounder, University of Denmark, Uppsala University, Pathfinder Advanced Radar Ice Sounder, Alfred Wegener Institute) and ocean bathymetry (from single-beam data in dark blue),
and (b) BedMachine v3 bed topography sources, which include mass conservation (MC), kriging, Greenland Ice Mapping Project (GIMP) (Howat et al., 2014), RTopo-2/IBCAO v3 (Jakobsson et al., 2012; Schaffer et al., 2016), and bathymetry data from multibeam and gravity inversions acquired after the compilation of IBCAO v3.

The nearer to the shoreline, the more valuable the bathymetry data are for understanding on-shore topography, Morlighem said.
“What made OMG unique compared to other campaigns is that they got right into the fjords, as close as possible to the glacier fronts. That’s a big help for bedrock mapping,” he added.

Additionally, the OMG campaign surveyed large sections of the Greenland coast for the first time ever.
In fjords for which there are no data, it’s difficult to estimate how deep the glaciers extend below sea level.

(a) BedMachine v3 bed topography (m), color coded between −1500 m and +1500 m with respect to mean sea level, with areas below sea level in blue
and (b) regions below sea level (light pink) that are connected to the ocean and maintain a depth below 200 m (dark pink) and that are continuously deeper than 300 m below sea level (dark red).
The thin white line shows the current ice sheet extent.

The OMG data are only one of many datasets Morlighem and his team used in the ice sheet mapper, which is named BedMachine.
Another comprehensive source is NASA’s Operation IceBridge airborne surveys.
IceBridge measures the ice sheet thickness directly along a plane’s flight path.
This creates a set of long, narrow strips of data rather than a complete map of the ice sheet.

Savissuaq Gletscher area in the GeoGarage platform (DGA chart)

Besides NASA, almost 40 other international collaborators also contributed various types of survey data on different parts of Greenland.

No survey, not even OMG, covers every glacier on Greenland’s long, convoluted coastline.
To infer the bed topography in sparsely studied areas, BedMachine averages between existing data points using physical principles such as the conservation of mass.

Bed topography for different sectors of Greenland:
(a) the region of Savissuaq Gletscher, (b) Hayes Gletscher, (c) Illullip Sermia, (d) Mogens Heinesen N, (e) Heimdal Gletscher, and (f) Skinfaxe.
The yellow/red lines indicate the ice front position between 1985 and today from Landsat data, and the white dotted line shows the profile used in Figure 1.
The topography is color coded between −700 m and 800 m, and contours are shown every 200 m from −800 m to 200 m above sea level.
Some glaciers, such as the one 10 km northwest of Heimdal Gletscher, were not mapped using MC.

The new maps reveal that two to four times more oceanfront glaciers extend deeper than 600 feet (200 meters) below sea level than earlier maps showed.
That’s bad news, because the top 600 feet of water around Greenland comes from the Arctic and is relatively cold.
The water below it comes from farther south and is 6 to 8 eight degrees Fahrenheit (3 to 4 degrees Celsius) warmer than the water above.
Deeper-seated glaciers are exposed to this warmer water, which melts them more rapidly.

Surface and bed topography along six profiles (see white dotted lines in Figure 2) from this study (solid black) and bed from B2013 (dotted red, Bamber et al., 2013) and RTopo-2 (dotted yellow, Schaffer et al., 2016). Multibeam bathymetry data (MBES) are shown in blue.
The vertical lines show the ice front position between 1995 and today.

Morlighem’s team used the maps to refine their estimate of Greenland’s total volume of ice and its potential to add to global sea level rise if the ice were to melt completely, which is not expected to occur within the next few hundred years.
The new estimate is higher by 2.76 inches (7 centimeters) for a total of 24.34 feet (7.42 meters).

OMG principal investigator Josh Willis of JPL, who was not involved in producing the maps, said, “These results suggest that Greenland’s ice is more threatened by changing climate than we had anticipated.”

On Oct. 23, the five-year OMG campaign completed its second annual set of airborne surveys to measure for the first time the amount that warm water around the island is contributing to the loss of the Greenland ice sheet.
Besides the one-time bathymetry survey, OMG is collecting annual measurements of the changing height of the ice sheet and the ocean temperature and salinity in more than 200 fjord locations. Morlighem looks forward to improving BedMachine’s maps with data from the airborne surveys.

The maps and related research are in a paper titled “BedMachine v3: Complete bed topography and ocean bathymetry mapping of Greenland from multi-beam echo sounding combined with mass conservation” in Geophysical Research Letters.
This project received support from NASA’s Cryospheric Sciences Program and the National Science Foundation’s ARCSS program.

Links :

Thursday, November 2, 2017

How 16th-century European mapmakers described the World’s oceans

A 13th-century depiction of the world as a circle divided by into three continents, Asia, Europe, and Africa.

From Atlas Obscura by Genevieve Carlton

For some, they were an obstacle.
For others, they were an opportunity.

According to medieval mapmakers, the world was made up of three continents ringed by narrow bodies of water.
When the voyages of Christopher Columbus, Amerigo Vespucci, and Ferdinand Magellan uncovered continents previously unknown to Europeans, this posed a major problem for those cartographers.
But these explorers did not just stumble upon uncharted land—they also became aware of expansive stretches of ocean around the world.

 Bünting Clover Leaf Map.
A 1581 woodcut, Magdeburg.
Jerusalem is in the center, surrounded by Europe, Asia and Africa.

For the first time, Europeans were confronted with the realization that they lived on a blue planet, with 71 percent of the Earth’s surface covered by water.
The narrow strips of blue on medieval mappae mundi—also known as T-O maps, which showed the earth as a T centered on Jerusalem—were suddenly dwarfed by unimaginably vast oceans.
Stories about the European discovery of the New World are ubiquitous, but stories about the discovery of so much new water are much more rare.

 Map of Borneo by Pigafetta.

For explorers, these oceans were dangerous obstacles.
Attempting to traverse them could quickly turn deadly, as the sailors on Magellan’s expedition learned when only one of their five ships—and 18 of the original 280 crewmen—returned to Spain in 1522.
Antonio Pigafetta, one of Magellan’s surviving men, described this first Pacific Ocean crossing, which took three months and 20 days, in a report.
He wrote, “We only ate old biscuit reduced to powder, and full of grubs, and stinking from the dirt which the rats had made on it when eating the good biscuit, and we drank water that was yellow and stinking.”

 Claudius Ptolemy, 13th Century world map

The oceans also posed a problem for mapmakers.
Reports from explorers deviated wildly from pre-Columbian perceptions of the world’s water, as evidenced in mappae mundi.
The 1475 world map in Lucas Brandis’s Rudimentum novitiorum captures this older outlook on the world.
Asia, at the top of the map, represents one hemisphere, while wedges depicting Europe and Africa sit in the bottom half of the world.
The map was not intended to be representative; instead it focused on a Christian ordering of space with Jerusalem at the world’s center.
The world’s territories appear as hills, and in Europe, rulers sit atop them, with the pope in Rome shown holding a gold cross.
Asia and Africa, less well known to 15th-century Europeans, have more fanciful illustrations, including a pair of dragons, a burning phoenix, and a man-eating demon chasing his victim while clutching his severed arm.
On the map, the Mediterranean separates Europe from Africa and the rivers Don and Nile mark the divide between Asia and its neighbors.
Yet on this particular map, these bodies of water are marked by thin black lines and nothing more.
The only water seems to flow from the four great rivers at the top of the map, which represents the Garden of Eden’s Earthly Paradise.

A 1475 woodcut world map, published in Rudimentum novitiorum.

The discovery of massive bodies of water forced mapmakers to devise creative solutions.
One of the earliest strategies was to shrink the oceans.
Here, mapmakers borrowed from Columbus himself, who minimized his trans-Atlantic voyage by claiming that the crossing took only 33 days.
However, Columbus only counted from the Canary Islands to the Indies, omitting the 37 days spent traveling from Spain to the Canaries, which included repairs on two of his three ships.

Cantino planisphere (1502)

One of the earliest maps to show the New World, the 1502 Cantino planisphere, shrunk the Atlantic by showing Flores Island, the westernmost of the Azores, just slightly west of the jutting coast of Brazil, when in fact it is several degrees of longitude east of the Brazilian coast.

 Battista Agnese world map (1544)

Battista Agnese, a Genoese mapmaker who produced at least 100 hand-drawn atlases for wealthy patrons, also narrowed the Atlantic in his 1544 world map.
Agnese drew only 10 degrees of longitude between Brazil’s furthest east point and Africa’s furthest west, nearly halving the actual distance of over 3,000 kilometers (1,864 miles).
These cartographic manipulations consistently under-measured the Atlantic, minimizing the distance between the Old World and the New.

From 1570, a world map by Abraham Ortelius. Public Domain

Sixteenth-century mapmakers also invented massive “undiscovered” continents to fill the oceans.
Two of the most famous maps from the 16th century, Abraham Ortelius’s 1570 world map in his atlas Theatrum Orbis Terrarum, and Gerhard Mercator’s 1569 world map, (which introduced the Mercator projection) rely on this approach.
Produced less than a hundred years after the Rudimentum novitiorum, Ortelius’s map shows a completely transformed globe.
The shapes of the world’s continents, recognizable to our contemporary eyes and now divided by the grid of latitude and longitude, are arranged with north at the top, a convention that only emerged in the 16th century.
The least familiar part of the globe is its southern stretches, which Ortelius labels “Terra Australis Nondum Cognita,” or southern land not yet known.

 1604 copy of 1602 Kunyu Wanguo Quantu

Both the Ortelius and Mercator map admitted that the world’s oceans were vastly larger than those shown on any pre-Columbian map, but both also hypothesized a massive southern continent to “balance” the landmasses north of the equator.
Mercator made this explicit in 1595, when he wrote, “it was necessary for such a continent to exist below to Antarctic Pole, which … would balance the other lands.” Europeans were so certain that this continent existed that Australia, first spotted by Europeans in 1606, took its name from the Latin term for Terra Australis.
These imagined continents did not just multiply the Earth’s land—they also limited the disturbing vastness of the world’s oceans.

 Gerard De Jode Universi Orbi seu Terreni Globi (1578)

Other cartographers embraced the ocean’s blank canvas in a different way: by emphasizing just how empty it was.
In addition to minimizing the size of the Atlantic in his beautifully-colored maps, Agnese painted the land a rich green, depicting the mountains, rivers, and lakes that dotted the territory.
On the land, water is drawn in brilliant blue, and the Red Sea and the Gulf of California are colored red, a convention borrowed from mappae mundi.
The ocean, by contrast, was largely blank, the untreated vellum standing in for water.
Agnese did scatter a few islands throughout and used the blank space to highlight Ferdinand Magellan’s route as he circumnavigated the globe.
But his map implies that Magellan did not discover anything notable in the ocean; rather, the ocean was an emptiness between “real” places, defined by the absence of land rather than containing anything worth recording.
Agnese’s unknown land, or terra incognita, which also faded into blank vellum, was visually identical to the explored oceans, perhaps hinting that the ocean was ultimately unknowable.

"A Complete Geographical Map of all the Kingdoms of the World" (坤輿萬國全圖),
the first Chinese world map, 1602

But the seeming blank space of the ocean signified more than peril and emptiness—it also posed an opportunity for enterprising mapmakers.
Blank spaces on the map could be filled with promotions for the map’s creator or his hometown.
The French royal cosmographer and mapmaker André Thévet manufactured not one but two fictional Thevet Islands in the Atlantic in the 1580s.
Similarly, in a 1558 book with an accompanying map, Nicolò Zeno, a Venetian nobleman from a flagging family, alleged that his familial predecessors, Nicolò (his namesake) and Antonio Zeno, had landed on the invented island of Frisland and led voyages in the North Atlantic that discovered the New World in 1380, over a century before Columbus’s Genoa or Vespucci’s Florence could claim the glory.
And on his 1560 world map, Paolo Forlani, one of Venice’s most active mapmakers, used the wide oceans to promote Venice by sprinkling the Atlantic, Pacific, and Indian Oceans with Venetian galleys, clearly not designed for transoceanic voyages.
The ships not only filled the water, but they also proclaimed Venetian dominance in an era when Venice had already lost the race to colonize distant territories.

Forlani’s map of North America from 1566. Public Domain

Mapmakers also explored a range of design techniques to fill the oceans.
Giovanni Lorenzo D’Anania’s 1582 map of the North Atlantic not only populated the waters with imaginary islands, but also filled the sea with dark dots and large labels for the land, minimizing the impression of blankness.
In his 1566 map of North America, Forlani similarly peppered the Atlantic with islands both real and invented, expanded the size of North America, and dotted the waters on his engraving to avoid the impression that the oceans were simply blank.
He also made the Pacific much smaller than the Atlantic, placing the island of Japan halfway between North America and Asia.

Map of the Southern hemisphere, 1593 by Gerard de Jode

These mapmakers and the explorers who crossed the newly found oceans saw the water both as an obstacle, separating Europeans from their destination and posing countless dangers, and as an opportunity.
A blank space on a map let a mapmaker reinvent himself, much like pirates who roamed the seas, by manufacturing islands or adding flourishes to promote his city.
And when mapmakers signed their works, they almost always did so in the ocean.

Links :

Wednesday, November 1, 2017