Crossing the Atlantic, again

The Atlantic Ocean is huge, it covers 20% of our globe, stretching all the way from Greenland in the north and almost to Antarctica in the south. To the west is North and South America, to the east Europe and Africa.

During the One Ocean Expedition, Statsraad Lehmkuhl has so far crossed the Atlantic Ocean three times. First from the Canary Islands to the Caribbean, then from Newport to the Azores, then from the Azores to Brazil.

Now the ship is underway from Cape Town in the very south of Africa, to Natal in the far east of Brazil, crossing number four. This is a long leg, 6320 kilometers, at least. A sailing ship cannot be expected to sail in a straight line, the wind decides. The crossing is estimated to take 29 days, and so far everything is going according to plan.

A complete circle

On 25 January, Captain Marcus Seidl wrote this in his daily report:

- We will be crossing the longitude on which we started the expedition from Arendal on August 20th, 2021, sometime this evening. We will therefore for all practical purposes have sailed around the world – which we believe is worth mentioning.

We have checked the log, 8.77 degrees east was crossed on January 25 at 20:27 Norwegian time.

St. Helena

A submarine ridge runs from north to south along the whole Atlantic. The Mid-Atlantic Ridge rises 800 meters above the seabed, but is actually a fissure. This is where the tectonic plates beneath North and South America, and Europe and Africa meet.

200 million years ago, what was a single large continent, Pangaea, broke into several parts that began to slide apart. It is still easy to see that South America and Africa fit together like puzzle pieces.

The fissure is constantly expanding by a couple of centimeters a year, and from it flows volcanic material that build new seabed.

Larger volcanic eruptions occasionally reach all the way to the surface, forming new islands. Iceland came into existence in this way, as did the Azores, Bermuda, and St. Helena, which Statsraad Lehmkuhl spontaneously decided to visit in the beginning of February.

Riding currents and the trade winds

North and south of the equator ocean currents run from east to west. North of the equator the current is part of a huge vortex that rotates clockwise, covering the entire North Atlantic. South of the equator is a corresponding vortex that rotates counter-clockwise.

Below is a realtime model of the ocean currents in the South Atlantic. The warmer the colour, the swifter is the current. The movement indicates the direction of the currents. Map: Earth Nullschool.

The Benguela Current is part of this southern vortex, originating off the coast of South Africa, where NERSC and ESA studied the ocean currents when they were on board the Statsraad Lehmkuhl in January 2023.

On her way north-west across the South Atlantic, the Statsraad Lehmkuhl is riding both the southern vortex and the trade winds.

- The nice wind that we picked up yesterday afternoon has stayed with us and looks like it will do so for the next few days before we pick up the weaker southeast trade wind further north, wrote captain Marcus Seidl in his log on January 24, when the ship was off the coast of South Africa, and in the Benguela Current.

Three days later, the captain was still satisfied:

- The outer edge of a high pressure area continues to generate a nice and stable south-easterly breeze, and with the Royals (the uppermost square sails) set, we are sailing nicely northwest-ward at just above the average necessary speed needed to maintain our schedule, he wrote.

Below is a real-time model of the wind and precipitation in the South Atlantic. The colour indicates the amount of precipitation. The movement indicates the speed and direction of the wind. Map: Earth Nullschool.

Statsraad Lehmkuhl is sailing with the wind coming in aft from the southeast, perfect for a sailing vessel. The heat from the sun shining directly overhead causes the air to rise above the equator. The rising air needs to be replaced, and there is a constant wind blowing in from the north and south.

Since the earth rotates, the wind direction is shifted a little to the east. It is these so-called trade winds that Statsraad Lehmkuhl rides. According to the forecast the ship can enjoy this favorable wind all the way to Natal.

Hot and humid

On board they have already noticed that the climate is slowly changing.

- Now that we are moving northwards from the subtropics to the tropics, we are gradually getting more squall activity, humidity and somewhat higher temperatures, Seidl wrote in his log on February 4.

The air rising above the equator brings with it a lot of water vapour. When it gets high enough, the rising air is cooled, the water vapor turns into water droplets, and clouds and rain form. So have your rain gear ready cadets.

Number five

Statsraad Lehmkuhl will arrive in Natal on February 17. February 20 the voyage continues north to Puerto Rico, and March 16 the ship sets out on her Atlantic crossing number five. This leg brings her to Lerwick in Shetland, where the ship is scheduled to arrive April 10.

Lerwick was not in the original sailing plan, but to make sure that Statsraad Lehmkuhl shines when she sails into her homeport Bergen, Norway, April 15, a short stop in Shetland was decided. Three weeks in the North Atlantic in early spring can take its toll both on the rigging and the hull.