Maelstrom!
A Research Paper by Masha Falkov
Sucking, howling, spitting, whirlpools in fixed geographical positions that sailors loathe and fear! Engulfing helpless ships as the passengers gaze in agony at impending doom of the approaching vortex below, threatening to tear them to shreds! Most scientists state that this is all nothing but horsefeathers of mythology, thought up by seafaring, exaggerating Vikings and artistic writers like Poe, Homer, and Verne. The whirlpool is nothing but a convergence of tides in a narrow, shallow strait that lies between two deeper areas…with powerful currents, yes, but nothing so outrageous as a huge swirling funnel, most will tell you. However, ships have been lost, people have been claimed, and some- such as the enormous Corryvreckan in Scotland- have even been classified as “unnavigatable” (in this case the Royal Navy did so). Nothing but a convergence of tides…
Because the most powerful whirlpools with a vortex are extremely difficult to observe and examine at their most ferocious, there was little scientific information on how they behave- how fast the currents travel, how the funnel is created, and especially what happens at the very depths of the waters (the Moskenstrom fjords can reach from 20 meters to 500 meters in depth) The whirlpool itself lasts a relatively short amount of time- anywhere from a couple of seconds to an hour, and in nearly all cases, one would have to be in the vicinity of the maelstrom to observe it- typically not on the safety of land! Diving oceanographers have been denied permission by their organizations many times to study the Corryvreckan because of the swift change from a calm slack tide to a churning maelstrom of an ebb tide (The Pinnacle is the highest point in the Corryvreckan gulf waters and is a popular spot for expert divers as well). Combined with this and the diminished interest in the behavior of the maelstrom, it was much easier for a scientist dismiss stories of whirlpools’ ferocity as mere exaggeration rather than be caught with a lack of numbers.
This has changed somewhat recently, in a renewed interest of how a maelstrom works and its effect on the sea and sea life, mainly because of advances in technology, which allow for (relatively) easier and more accurate observation: satellite imaging of water temperature, speed, and direction, as well as depth sounding. Also, computers have advanced to become much more powerful machines which would permit physicists to generate accurate models of a whirlpool and how the currents and the height of the sea floor affect it- as well as other factors such as wind and air pressure. Nature Magazine did a study on the Moskenstrom in Lofoten, stating that,
“No substantial modern studies of this strong tidal current have been
reported. The Norwegian Pilot Book
provides some information albeit limited of scientific knowledge.
We have therefore developed a
high-resolution depth-integrated tidal model…”
On an expedition in early 2000, for a documentary series known as “Equinox”, several experiments were done with the Corryvreckan, as will be discussed later.
In physics of water, a whirlpool is a free vortex of the two types of vortices- the other being a forced vortex. Both are water whirling in a spiraling motion: the forced vortex is spins by a centrifugal pump (like spinning a spoon in a cup of tea to move the water), and the free vortex has its flow due to change in height or in pressure- like the form in a bathtub. The maelstrom is a free vortex.
There are several factors that contribute to the creation of a whirlpool with a strong vertical motion. The first is a change in tide, in a narrow channel with a large mass of water. In the Moskenstrom, about 370 million cubic meters of water are transferred in 6 hours. This would create a swift current ranging from 6 to 22 knots. Next, a steep change in the depth of the seabed is necessary: in the Corryvreckan, which means “speckled cauldron”, the top of the pinnacle reaches just 30 meters below the surface in contrast with the chasm dropping to over 200 meters. This is why whirlpools in the open ocean have less of a threat to ships- they would not develop a vortex because of the fairly uniform depth. In essence, an enormous mass of water exits a narrow channel, currents attempting to push out all at once against currents trying to enter- the tide would ebb before it would flood or vice versa. As the currents are in motion, there is suddenly a dramatic drop in depth- such as first the rise in the strait between the Mosken and the Vaeroy islands in Lofoten, and then the seafloor 500 meters below- similar to a drain in a bathtub. Finally, wind can affect the maelstrom as well, inhibiting or accelerating the flow of a current. All these factors contribute to the behavior of a maelstrom.
The Corryvreckan Gulf in Scotland, which houses the whirlpool featured in the 1945 film, I Know Where I’m Going, contains an irregular bottom, with a rise between the islands of Jura and Scarba from a sea floor of 219 meters in the gulf (a huge hole) to 70 meters around a large, conical obstruction 50 meters in height known as The Pinnacle. This is a popular site for expert divers and is considered one of the most dangerous dives in the United Kingdom. Its roar is claimed to be heard at least 5 miles away, and during the equinox tides, it can fill the Gulf.
Here is a perfect example of the relationship between a narrow channel through which a large amount of water must flow during a tidal change and a bottom with varied height- but also humps, holes, and a large pinnacle to impede the current. The Pinnacle plays a large role in the behavior of the whirlpool, creating an up flow with its steep eastern side. The force of the Corryvreckan is tremendous. Spread out throughout the passage and the western Gulf are small depressions called boulder holes with rocks the size of basketballs situated in them. It was determined that the force of the whirlpool had actually pushed the boulders at the bottom, forming
the deep spots over time- and that the currents in the Corryvreckan penetrated as deep as 120 meters in the channel and 200 meters deep in the Gulf.
Even the most experienced divers dare not venture far from the Pinnacle-
the anchoring site for their ships- to view the sheer drop into the depth of the
Gulf during the short calm of slack tide lest the ebb begins and they run out of
time (in fact, on the www.ukdiving.com.uk,
divers are warned to watch for crustaceans- “when
they disappear, it’s time for you to go, too.”). The Equinox expedition determined in an experiment using a
human dummy and a depth scale that anything that is caught in the vortex and
cannot escape is sucked straight to the bottom when the depth scale went over
200 meters and the dummy was resurfaced with much gravel from the sea bottom in
its compartments. If a diver were
to be placed in such a predicament, the swift rush to the bottom would give no
chance to adjust the pressure in the oxygen tank would knock him or her
unconscious, drowning them ultimately. According
to the United Kingdom Diving web page, there have been many such deaths in
recent years.
Shipwrecks are also common. George Orwell nearly lost his life in 1947, when he and several of his friends took his boat through the passage and he miscalculated the tide.
The
motor to the boat was lost, and the boat was overturned.
Luckily, the group ended up only being stranded on a small island until
some lobster fishermen rescued them. The
Corryvreckan, classified unnavigatable as mentioned above, had caused 50
emergencies for the Royal Navy’s lifeboat in the past 10 years!
Edgar Allen Poe and Jules Verne romanticized the Moskenstrom, located in the Lofoten Archipelago in Norway, between the islands of Mosken and Værøy islands, and the Saltstraumen, located in the Saltstraum Channel. In the Saltstraum channel, the difference in the height of the water between the inside and the outside of can range from 1 to 3 meters. The current in the channel can reach 20 knots, and ships take caution when navigating it. Of course, small sailboats must take much more care in this area than large boats with engines- but even freighters can face problems with steering. It is understandable why sailors of the past would fear the Moskenstrom with panic- their speed was dependent solely on wind and current, and if those failed them in the maelstrom they would be caught in the vortex. Today, there are timetables and information in newspapers about when passage is safest through the most powerful whirlpools in the world.
The current in the maelstroms is most powerful during the new and full moons, when the tide is the greatest, and the saying that it is at its strongest on Good Friday is for good reason: at that time the gravitational pull from the sun and the moon is the greatest.
The Moskenstrom and the Saltstraumen, as well as many other such maelstroms, is a haven for sea life due to the nutrient-rich waters known to accompany whirlpools due to the high turbidity and rough current in which certain algae and bacteria thrive. Fishing villages line the Lofoten coasts and the areas surrounding the whirlpools are a prime target for both sport fishermen and commercial fishers. Travel agencies will claim that one can merely dip their bait in the water and a fish will bite. There are also incidents where the deep-sea redfish, which reside in the 500meter deep fjords, will swim to the surface in certain weather conditions and will die immediately from the rapid change in pressure. Fishermen would then pick their floating bodies off of the surface of the water.
In the Lofoten Museum, there is a list of hundreds of people who have been drowned in the Moskenstrom, and also a display of different ships that have been sucked to the bottom- some double-masted.
There are many other treacherous vortical whirlpools around the world- off the coast of France, the Charybdis in the Strait of Messina, Old Sow in the mouth of the Bay of Fundy, in Japan, and the Phillipines- however, they all have their own story, unique behavioral traits, and culture surrounding them.
The Viking legends were written with quite a bit of truth in them, although a bit exaggerated. One does not feel the earth tremble a dozen miles away during the Corryvreckan’s most violent hours, although the roar can be heard occasionally from that distance during a howling storm. Edgar Allen Poe’s story, “Descent into the Maelstrom”, though accurate in landscape was based more on imagination than science as he was more concerned with creating suspense- his maelstrom was many times the size of the 45-yard Moskenstrom. The danger that the whirlpools posed to ships was real, however, especially before the days when motors were used, and the deaths numerous. Therefore, despite many exaggerations in literature and legend, the actual power of the maelstrom should not be ignored and passed off as a relic, and should be treated with respect.
Bibliography:
Study on current speed, tidal movement between Mosken and Vaeroy, complete with tidal models
Study of the Moskenstrom with a literary focus, emphasizing Poe and Homer
Collection of people’s experiences with the maelstrom, various bits of facts that enthusiasts and researchers sent in.
History, tidal movement, and actual names and numbers of the deaths and shipwrecks.
Has a good description of the Corryvreckan, as well as maps describing the area in terms of depth and points of interest from a diver’s point of view.
http://channel4.com/equinox/seas_transcript.html
Results of diving experience by those who dove into the maelstrom for this expedition and the dummy experiment as wellas views of many scientists on how a maelstrom works and where the power is expelled.