Location: Richard's Bay, South Africa
Greetings, this is David Malcolm, tuning in from sunny (and rainy, and windy, and somehow multiple at the same time) Richard’s Bay, South Africa! I’m here with the daily reassurance that your loved ones are happy, safe, and, as Wes has put it, having a ‘litty’ time aboard Vela as we prepare to ride the Agulhas Current down to Cape Town. If the weather (and its aforementioned mood swings) allow, we should be able to set the sails and begin our ride southwest toward Cape Town tomorrow (just in time for me to make that Korean Breakfast Fried Rice I’ve been wanting to make for three months, score!).
From what I understand of sailing, it should be really cool passages from here on out, as our speed will be augmented by the physical forces that contribute to the Agulhas’ famous speed. The Agulhas current is the western boundary current of the Indian Ocean gyre. As a western boundary current, it gets sped up by a peculiar physical phenomenon known as ‘western intensification.’ The phenomenon occurs because, as the Earth rotates, different latitudes rotate at different speeds (latitudes closer to the equator move through space much faster than latitudes closer to the poles). As water currents move across latitudes, they experience an apparent deflection in their path as the Earth under which they are moving changes speed. This deflection, known as the Coriolis Effect, causes currents moving between latitudes to curve to the left in the southern hemisphere and right in the northern hemisphere. The strength of the Coriolis Effect, as it’s based on the fact that different latitudes travel at different speeds, depends upon the difference in those speeds between the latitudes over which the current travels. This results in the Coriolis Effect being stronger towards the poles (where speed increases rapidly from 0 km/hr at 90 degrees latitude to 800 km/hr at 60 degrees) than towards the equator (1600 km/hr at 0 degrees compared to 1400 km/hr at 30 degrees) The weaker equatorial Coriolis Effect results in all the currents moving from the equator poleward (the western boundary currents, like the Agulhas) to be concentrated in a much narrower surface area than their opposing eastern boundary currents, which get spread out by a stronger Coriolis Effect. Since the same volume of water passes through the western and eastern boundary currents, but the western boundary current is much narrower, like a garden hose when you stick your thumb over the opening, the water moving through the western boundary current has to travel much faster relative to the other global currents. That speed will give Vela the boost to travel much greater distances per day over these next passages, allowing us to comfortably travel the 340nm between Richard’s Bay and East London in a much faster timeframe than we’ve traveled throughout the trip so far. Weather allowing, we should be at our next stop in a relative blink.
Ah, blogs… the perfect platform to force a captive audience to listen to me write about science… warms my heart 🙂 Oh, what happened today? You want to hear that, too. Yeah, it was a good day! We all practiced our Emergency First Responder skills, the students got ice cream, we finished passage preparations, and we figured out that Allie has a funny laugh when she’s getting her back cracked. Good times, good times at Tuzi Gazi Port. Everyone’s watching the Hunger Games movies now (they were really excited about seeing the new one at the theater close to the marina in Cape Town), so I have to get back to avoid telling them that I haven’t seen any of them yet. Until next time!