The link between ocean currents and the Dutch, so called, skating fever

Water in the oceans is not only connected, but it actually flows around like an enormous rubber band. These flows have a huge impact on weather. New York and Madrid are situated at the same distance from the equator, but in New York it can be terribly cold in winter. The typically boring wet winters in the Netherlands (when actually everybody wants to skate desperately  are the result of the Gulf Stream, a warm flow of water originating from the Caribbean which flows as north as North Norway.

Rough figure of the ocean currents, the thermo-haline

circulation. Above is an animation of the ocean currents.

Only the last decade scientists could get a good grip on the surface currents in te oceans. Since a ship lost a container with rubber duckies in 1992, the research speeded up a lot. In the years since the container got lost, these friendly floatees washed ashore in Asia, North- and South America and Europe. Lately, scientists use floating measurement tools with satellite connection to map the ocean currents in much greater detail.

The rubber duckies which fell in the water in January 1992 floated around
the oceans. The duckies wash ashore on all continents since.

Deeper in the oceans are more currents in different directions. It was impossible until now to map all the currents and to find out where all ocean water flows to. Small variations in temperature and salinity are the engine of the ocean circulation. Also prevailing winds like trade winds play a role in driving the ocean currents.

A increasing amount of melt water from the arctic regions could disturb these currents. The level of salinity changes and possibly the water from the Gulf Stream will experience difficulty to sink down in the North Atlantic ocean. Al Gore showed the phenomenon pretty nicely in his 'An Inconvenient Truth'.  If the Gulf Stream would come to a stop, or would cease to flow as North as today, winters in the Netherlands might get a lot colder. This is something skate fanatics are already counting on! But climate experts think that the slow and continuous melt of icecap of Greenland in the next centuries will not have this effect. The Gulf Stream will not stop as can be seen in the animation of Al Gore. It will probably become slightly weaker, not much, but measurable...

More information:
- Oceanographic science done by beachcombers: beachcombersalert.org/RubberDuckies.html
- The book by Curtis Ebbesmeyer and Eric Scigliano about the obsession for rubber ducks which wash ashore and how this obsession changed oceanography for ever: Flotsametrics.com

A part of this text is written in preparation for the upcoming exhibition Climate Stories in Museon, The Hague. This exhibition will open in spring 2013. More information can be found at: klimaatverhalen.nl

De Nederlandse versie van deze blogbijdrage: Oceaanstroming en Elfstedentochten

Sinking volcanoes in the Pacific Ocean

How is it possible that tiny little circular islands exist in the middle of the Pacific Ocean? Even on a sea floor which is 4 or 5 kilometer deep? These little round islands are atolls. They have been build up from volcanic rock and corals for over millions of years. Charles Darwin already published a theory on the formation of atolls over a century ago. His vision is still generally accepted.

The atoll Marakei, which was visited by curators
 from Museon in the Hague in October 2012.

The theory is in fact that a volcano slowly sinks down into the ocean and the island slowly changes shape. At first this mountainous island is a separate volcano at sea. When the (millions of) years pass this island slowly sinks down because the sea floor sinks down as it becomes older. Also erosion helps to break down the volcano. It changes into an smaller mountain with a barrier reef around it. This process continues until the mountain is long gone and the circular coral reef is only thing left over.This is called an atoll.

The steps in which a volcanic island
changes into an atoll.

The island Bora Bora. The growing coral reef around the island
is already visible as a ring around a shallow lagoon. In the
middle are still the remains of an old volcano.

Darwin reasoned that corals which are located around the volcanic island, slowly grow and follow the sea level. At the same time the island slowly disappears under water. Once the volcano is completely under water, the corals form an atoll. The ring of corals is called a barrier reef, because the lagoon in the middle is an shallow area. There corals cannot grow as good as at the edge of the island. The lagoon often contains brackish or even sweet water.

The islands of Hawaii show from East to West this development towards
becoming atolls. The youngest island, Hawaii, is a very active volcano.
The slightly older islands not anymore. Towards the West the islands are
older, eroded and further down in the ocean. The original volcano is not
visible above the water anymore.

More information:
- Nice explanation of the development of atolls on the beach: YouTube.com/watch?v=btRCAQHqbdY
- Colleagues of Museon in The Hague visited an atoll in Kiribati for in preparation for an exhibition. The text in this blog item is inspired on their request for more information about the development of atolls. Check their work for Museon on: Klimaatverhalen.nl

Nederlandse versie van dit artikel: Wegzinkende vulkanen in de stille oceaan.