The ground floor of the Cape Agulhas lighthouse is devoted to a lighthouse museum and curio shop/tourist information centre. The museum is small, but well worth investigation if you’re a lighthouse buff.
There is a large number of posters on display, covering the history of the Agulhas light and the surrounding area, as well as lighthouses around the world. There is also a selection of lenses and other historical lighthouse and rescue equipment.
This will be a quick newsletter as we are downwind of a raging vegetation fire and the smoke is unbelievably thick. Even our tortoises are going to spend the night indoors. Firefighters, many of whom are volunteers, have been have a rough time of late and I admire their endurance, skills and management of these situations.
We had really good conditions in Hout Bay last weekend with clean and cold being the main factor. 8 degrees celcius is chilly but the viz was easy 15 metres.
The south easter has humped all week long and False Bay is a little messy. The visibility in the yacht basin today was actually very good but I think the rest of False Bay would have been messy. The yacht basin is protected from the south easter by the naval harbour.
The forecast leads me to believe that Hout Bay will be good on Saturday and False Bay on Sunday. I would also like to slip in a night dive on Saturday if the conditions permit.
Much of my recent Arctic obsession has been historical, with a related interest in the hostile environment that has stymied (and killed) so many explorers over the centuries. Bruce Parry is a British documentarian (didn’t know that was a thing, but it seems fun) who seems to be dearly loved and some kind of national institution to the Brits. After watching this five-episode BBC series on the Arctic and its people, we could understand his charm.
Parry visits people living in Siberia, Greenland, northern Canada, Alaska, and the far north of Norway. He throws himself into their activities – whether rounding up reindeer, hunting for seals on the ice, fishing in Alaska (I had some serious lifestyle envy at this point), or racing up mountains. He is sensitive and respectful, and seems to forge genuine bonds with the families he visits.
The common thread that marks the lives of many of the tribes and peoples’ that Parry visits is that climate change, and the encroaching changes wrought by the pace of modern life, are challenging their traditions and lifestyles. Having lived sustainably off the land for generations, these people’s movements, traditions and futures are now circumscribed by all sorts of interventions from modern society. Not least of these is a lack of understanding of and respect for how they live.
Tony and I found much to discuss – for example, after the episode covering a traditional whale hunt in Alaska. Is there a difference between Japanese industrial whaling and an Inuit community’s subsistence hunting for a couple of whales a year, done with reverence, prayers, and gratitude for the whale, whose bones will be scraped clean by polar bears after the entire carcass has been distributed in the village? Is it possible to kill an animal as large as a whale, humanely? Is all whaling wrong? These are difficult questions but it is worth grappling with them. As my friend Tami has exhorted me in the words of Rilke (in a different context, admittedly), “live the questions!”
The series was filmed over the course of a summer, during which time much of the usual ice that marks the Arctic landscape was absent. The look of the landscape initially puzzled (and disappointed) me – without the icy covering, everything looks quite barren and gravelly!
You can get the dvd here (South Africa), otherwise here or here.
Rescue Warriors: The US Coastguard, America’s Forgotten Heroes – David Helvarg
Much of this book reads like one of the Reader’s Digest “drama in real life” stories that I used to devour from the magazines that my granny brought us when she came to visit. (She’d also bring a packet of Sparkles or Cadbury Eclairs.)
Journalist, activist and former war correspondent David Helvarg (who also wrote Saved by the Sea and 50 Ways to Save the Ocean) spent two years embedded with various branches of the US Coastguard in order to experience their work.
I was wrong. The mandate of the US Coastguard is to enforce maritime law (this is its primary difference from the NSRI) as well as to perform search and rescue operations. Viewers of the Deadliest Catch series will be familiar with the rescue work of the Coastguard in extremely challenging conditions. As a result of its law-enforcement mission, the Coastguard uses weapons and provides a lot more military-style training than you’d expect from a pure rescue operation. The Coastguard falls under the department of homeland security and operates cutters (with guns), icebreakers, small boats, helicopters, and other aircraft.
Helvarg’s conservationist tendencies shine through in several parts of Rescue Warriors, and he does not shy away from confronting the aspects of the Coastguard that he finds problematic. His contention is that the Coastguard receives far less publicity than it deserves. This book goes some way towards bringing attention to the individuals who have saved tens of thousands of people during Hurricane Katrina, via water evacuation during the September 11 attacks, and in countless other less well-known emergency situations.
This is a gripping read which I thoroughly enjoyed. I was amazed by the amount of funding and equipment that the Coastguard has at its disposal compared to the NSRI, even though the organisation is actually badly underfunded, especially when considered relative to the rest of the United States war machine. I was also impressed by the egalitarian approach that draws many women to join the Coastguard and enables them to rise in its ranks. The Coastguard made all its jobs available to women in 1977, something which other branches of the military have not yet done.
You can get a copy of the book here (South Africa), here or here.
Perhaps you have wondered what causes the patterns of strange coloured water in False Bay during the summer months. Perhaps you have dived in it, and wondered why sometimes you can’t see your hand in front of your face! Wonder no more – I am here to help.
Frequent visitors to and residents of the shores of False Bay will observe that at certain times of the year, the ocean is marked by bands and arcs of sharply contrasting coloured water. This phenomenon is known as a colour front. In oceanography, a front is the interface or boundary between two separate masses of water. In this case, the water masses are easy to discern, because they are of different colours. There are usually other characteristics of the water on each side of the front that differ, too. Fronts are either convergent (the water masses are moving towards each other) or divergent. The presence of marine debris (like pieces of kelp) at the front boundary suggests that it is convergent.
Causes of colour fronts in False Bay
Prior to 2005, there was much conjecture about the causes of these fronts (including the usual pollution bugbear), but little evidence to support any of the theories. By sampling, the fronts were found not to be caused by pollution, or by plankton blooms in the surf zone. It was known that a colour front was most likely to occur in False Bay after a period of southerly or south easterly wind lasting a few days. October and November seem to be prime months for the phenomenon.
When a large, obvious colour front arose near Simon’s Town in November 2005 with milky green water on one side, and darker blue-green water on the other, researchers from UCT and IMT sprang into action, sampling the water on each side of the boundary so that they could measure its characteristics. Speed is of the essence in these situations; colour fronts can disappear quickly. The one in the picture below is busy decaying – notice the smudged boundary.
Measurements revealed that the milky green water overlaid the clearer, bluer water, down to a depth of 11-12 metres (this will vary from front to front). The milky water did not extend to the ocean floor. Scuba divers around the Cape Peninsula will be familiar with the experience of diving through two or more layers of water, with varying turbidity (clarity) and temperature! (Here is picture of Tony and Christo diving near Oudekraal in the Atlantic that shows what the boundary between two layers of water can look like.)
The researchers found that the milky coloured greenish water was full of fine, almost neutrally buoyant particles of calcium-rich sediment. The green-blue water contained much less calcium, but relatively more silicon, which would suggest the presence of diatoms (a kind of phytoplankton – you can think of them as teeny tiny plant-like organisms) or sand in the water. The origins of the calcium-enriched sediment in the milky water are interesting: one source is from the shallows (less than 30 metres deep) of north western corner of False Bay, where the ocean floor is made up of rocks that are rich in calcium carbonate (such calcrete and limestone), some areas covered by a thin layer of sand.
The second probable origin for the particles of calcium-rich material is the interface between the sea and the land at the northern end of False Bay. The cliffs at Wolfgat/Swartklip at the head of the bay are made of calcrete, and at Swartklip the beach narrows to the extent that the cliffs erode directly into the water when the sea is high. Strong southerly winds create a wide (of the order of one kilometre) surf zone at Muizenberg and Strandfontein; a spring tide also adds to ideal conditions for the generation of a colour front.
The temperature of the milky water was found to be slightly (0.4 degrees Celcius) higher than the green-blue water. This measurement will also vary from front to front. The researchers speculate that the temperature difference could be because the milky water originated in the surf zone, which is shallower and therefore warmer, or because the high concentration of suspended particles in the milky water caused greater absorption of heat from the sun.
Here’s the tl;dr: strong southerly and/or south easterly winds, perhaps coupled with spring tide conditions, set up a very wide surf zone along the northern end of False Bay, which disturbs the sediment on the ocean bottom and drives the waves further up the beach than usual. Particles of buoyant calcium carbonate from the sea floor and eroded from the cliffs at Swartklip are lifted up into the water column, changing its colour to a milky-green shade. Wind-driven circulation patterns in the bay push the front from its original location in a southerly direction, towards Simon’s Town.
What to do?
Contrary to what your friends on social media may claim, not all colour changes in the ocean around Cape Town can be attributed to a giant sewerage plume. Hardly any of them can, in fact. In summer, the reason for the ocean looking green, red or even brown is likely to do with a plankton bloom of some description, or related to suspended sediments (as in this case) or other naturally arising material in the water. Instead of using this as an opportunity to become hysterical on the internet, how about celebrating the incredibly dynamic system that we can observe, living near the ocean? Drive up a mountain next to the ocean and take in the spectacle from on high. Dip your face in the water and see what it does to the viz. Take some pictures for posterity. And – if you don’t know what’s causing it – try to find and question someone who does know, like a scientist, or consult a good non-fiction book, to find out some facts.
The south easter has been blowing for a while now… Almost non stop. Windy, our wind generator at home who generates about a third of our monthly electricity requirements, has been having such a great time that she almost fell off the roof this week. She brakes herself when the wind reaches 78 km/h, and on several occasions the wind gusts exceeded that.
The Atlantic went from clean and cold, to cleaner and colder. The water colour in False Bay is not that bad but the surface conditions are pretty hectic. Fortunately I have had a lot of students requiring pool time so we have at least been getting wet.
There is wind and some swell for the weekend but I do believe that there is a possibility that Hout Bay will be good on Sunday. I have a bunch of students so will plan for both morning and afternoon dives, wind and swell dependent.
If the wind is driving you crazy too, check out the suggestions for land-based marine-related entertainment in last week’s newsletter.
Owen Beattie is a Canadian forensic anthropologist (a real one) who exhumed the bodies of three members of Franklin’s expedition who died and were buried on King William Island in the Arctic. Beattie’s team visited the island in 1984 and 1986 to work on the exhumation, examination and reburial of the three men. Buried in the permafrost, the bodies were remarkably well preserved (that’s a picture of one of them on the book’s cover).
Frozen in Time describes Beattie’s search for evidence about what led to the death of the men on the expedition, as well as providing a historical context for their search. The rigors of working in the Arctic – even in summer – and the historical, biological and cultural insight that can be obtained from the examination of dead bodies makes this a gripping read. You can read it as a stand-alone account of the Franklin expedition and its grim ending – no prior knowledge is required. Canadian writer Margaret Atwood’s introduction provides a beautiful interface between history, science and the deeper truths about ourselves that are revealed by the imperative to explore the Arctic.
These photos were taken on a day when I was trying my best to work on the boat, but cats were swarming all over it as though it was the Jolly Roger pirate party boat at the Waterfront.
Size is not an obstacle when you have determination. Here is Junior demonstrating that the opening of the inspection hatches under the bench at the back of the boat is almost exactly the size of his upper body.
The Cape Agulhas lighthouse is the most visually pleasing lighthouse that I’ve visited so far. Tony and I visited it while we were staying at De Hoop last September.
Cape Agulhas was named by the Portuguese from their word for needle. During the 1500s, when they were plying Southern Africa’s coastline, the magnetic declination in the area was approximately zero, meaning that there was no deviation between true and magnetic north, and the compass needle pointed to true north.
(Technical sidebar: Cape Agulhas lay on an agonic line during the 1500s. An agonic line is a line on the earth’s surface along which the magnetic declination or variation is zero. Earth’s magnetic field slowly changes, and with it the positions of the north and south magnetic poles. For this reason, the variation between true and magnetic north at a point on the earth changes slowly over time. You can examine a map of historic declination over the last 400-odd years here – if you scroll it back to 1590 you can see the green line through Cape Agulhas.)
The lighthouse is within walking distance of the southernmost tip of Africa inside the Agulhas National Park, and was built on land donated by Michiel van Breda, a local landowner (for whom Bredasdorp was named). Van Breda had experienced the trauma of shipwrecks along the stretch of coastline on his farm, with hundreds of dead bodies washing up after ships foundered on the rocky shores in rough seas. The shipwreck museum at Bredasdorp commemorates many of these wrecks.
The lighthouse was commissioned on 1 March 1849. It has a 7.5 million candela light that emits one flash every 5 seconds and has a range of 31 nautical miles. The lighthouse tower is 27 metres high, with a focal plane 31 metres above sea level. The tower is made of limestone with a white lantern house. By the 1960s the tower had deteriorated to such an extent that the lighthouse was temporarily decommissioned (its job performed in the interim by an aluminium tower), and restoration was undertaken. It was recommissioned in 1988.
The lighthouse is open to the public (also on weekends, which is unusual for a South African lighthouse) and contains a museum and a gift shop on the ground floor. The view from the top is well worth the climb.
We are back from a trip up north… Really far north – so far north that the temperatures, so I was told, were 0 – 2 degrees Celcius but to me felt like minus 50 degrees. It was great diving in False Bay this week in 22 degree water.
The weekend is a little on the questionable side as the wind and swell forecasts are not promising. I think the best option is going to be Table Bay, and If we go it will be to North and South Paw. I will take a look there tomorrow at the conditions and confirm late afternoon to those on the list if we are diving. Let me know if you’re keen to dive by email, text, or message in a bottle.