An article on Wired.com describes how the European Space Agency uses satellites to measure wave heights in the North Sea, where freak waves can damage wind farms, oil rigs, and ships. Mariners have spoken about giant, rogue waves for hundreds of years, but it’s only with the advent of automated means of measuring wave heights that the existence of such waves has been confirmed. The story of the Draupner wave, believed to be the first rogue wave that was actually measured (in 1995), illustrates just how recently we’ve been able to do this sort of thing.
Here’s a video explaining how satellites take their measurements and why it’s important:
The CMA CGM Alexander von Humboldt, one of the world’s largest container ships
I’ve written before about the Marine Traffic website, which uses the Automatic Identification System (AIS) that ships above a certain size are required to make use of, in order to track their location. We use it to find out about the ships that sometimes come into False Bay for shelter. Ship Finder is a similar, somewhat more user friendly variant of the Marine Traffic map. I find it a bit easier to use, especially when looking at a vessel’s path through time. If you really want to, you can see air traffic instead (warning: it’s terrifying and you may wish to unsee it)!
There is also OpenSeaMap, which is an offshoot of the OpenStreetMap project. OpenStreetMap is a crowdsourced project to create an editable world map that is free of charge. You can visit the OpenStreetMap website to see what it’s about. OpenSeaMap uses some of the OpenStreetMap data, but also includes marine information such as the location of lighthouses and buoys, and some quite limited AIS information. The map also purports to include tidal data, seabed profiles, and water depths, but is a work in progress.
Finally, there is FleetMon, which requires an email address in order to register. There are various account types, most of which require a subscription, as well as apps for Android and iOS (not free of charge). With a free account you can access FleetMon Explorer through your web browser, and it’s a rich AIS interface with a huge (nearly 400,000) vessel database and beautiful maps. You can create a “fleet” of vessels you’re particularly interested in, and track them around the world. However (and this is quite a biggie) you only get five minutes of FleetMon usage per day. If you want more, you have to pay.
I plan to spend Saturday boat diving (in False Bay or Hout Bay) with Divemaster candidates. Low viz and lousy surface conditions will apply. On Sunday we will launch at 7.00 AM and dive the MV Aster and the SS Maori, or if the conditions on the Aster are really good and the swell at the Maori not so good, we will dive the MV Katsu Maru.
Drawings of the SS Maori & SAS Transvaal
Sodwana
So far we have nine people heading to Sodwana at the end of April. Clare is confirming the booking with Coral Divers tomorrow, and will send out further details to those joining us. It’s not to too late to come along, but you do need to think quickly in order to secure accommodation, because this is a busy time for Sodwana. Let me know as soon as possible if you want more information. Warm water, lots of colourful marine life – what’s not to love?
Blue banded snapper in Sodwana
Dive report
The wind has made itself felt for most of this month and we have had only a handful of days with really good diving conditions. Never mind, at least there is always somewhere to dive in this city. We have had a weather station on our house since the middle of last year and it shows some very interesting trends. I think the primary reason for the lack of good viz on the Atlantic may have something to do with the fact the wind has been more southerly than south easterly for the last few months. Please note: having a weather station at home does not make you a weather expert, instead it gives you more things to wonder about.
Clovelly
This weekend looks more and more like an Atlantic weekend with the wind that we have in the forecast. Both Saturday and Sunday start off with 20-odd km/h winds and then it climbs during the day. Sunrise is still really early so an early start is what we will plan. Email or text me if you want to dive.
On Friday we are shore diving A Frame as the Divemaster candidates are working on a mapping project. On Saturday the boat will be in False Bay but is already full as we have a bunch of Open Water students to qualify. That leaves Sunday open for two launches to somewhere that we can dive without a white stick. If you want to be notified on Sunday morning as to whether conditions will permit us to dive, reply to this mail or send me a text message.
Last week’s diving
This weekend signals the end of most of the up country visitors’ vacation time, and life slowly goes back to normal. You can once again find parking at most of the beaches and and go back to swearing quietly at the idiots on the road because they could be your neighbour.
It’s been a week of really poor diving with swell, surge and low visibility. The Atlantic is not very clean, and nor is False Bay. The storm that hit the Cape2Rio Fleet did its best to fill the bay with kelp, silt and garbage. Today we have had some westerly winds which has helped to clean this up a little, and the forecast for the weekend is a southerly wind. That’s good in some places in the bay, and not so good in others. Today I was in the pool doing skills and equipment exchange with two Divemaster candidates. At least the visibility there was excellent…
Nick may have trouble equalising
Most of you will be aware that last weekend there was a serious diving accident on the wreck of the MV Rockeater in Smitswinkel Bay. The dive community is a small one, and even though we did not know the diver concerned, we have felt the loss keenly and Clare and I have spent a lot of time discussing it. The full details of what happened have not been released, but there is always something to learn when things go wrong, even from partial information.
When incidents like this occur there is a tendency for them to be swept under the carpet, as people tend to believe that it will cause harm to the dive industry. I don’t share this view. Finding someone to point a finger at has no value (and often there isn’t anyone who can be blamed), but a lesson learned has huge value to a diver who is still on the learning curve. Hopefully we are all still on that curve. Not everyone has a person in their life who understands scuba diving and with whom they can work through an incident like this. If you’d like to discuss it at all, please give me a call or drop me an email.
Remains of a large swell on Fish Hoek beach this evening
Sodwana trip in April
On a much happier note, we are planning a dive trip to Sodwana from 26 April to 30 April. We will stay at Coral Divers and do six dives (at least) over three days, with one day for travel on each side (fly to Durban, drive approximately 400km to Sodwana). This will be a busy time at Sodwana because of the public holidays and the fact that schools will be mostly closed that week, so we need to get into gear quickly on this one.
We’ve done this trip a couple of times before – read about one of those occasions here, and see what kind of diving you can expect here. A hint: it’s warm and colourful! You will need to be a confident boat diver, but an Open Water qualification is sufficient. If you’re interested let me know and I’ll send you more details – you only need to pay a 10% deposit to secure your booking, with full payment due 14 days before our arrival. The Coral Divers price list for 2014 can be found here.
Everyone needs something to look forward to at the start of the year… Think about it!
What will Google do next? They’ve taken their street view tool underwater, and have now taken their cameras on board the RV Falkor, a research vessel of Schmidt Ocean Institute, while she was moored in San Francisco. Click here to see the map showing the ship moored at the quay, and click on Street View at the top left corner (hover over the name of the ship in the corner of the screen if the street view block doesn’t appear) to access the interior of the ship.
The RV Falkor is a beautiful vessel – not sure how she stacks up against the SA Agulhas IIor RV Mellville. But research ships make me want to pack a bag and get on board!
In April this year white shark researchers Michael Domeier and Nicole Nasby-Lucas published a paper detailing some of their research into white shark migration patterns using data from satellite tags. The scientists show that white sharks in the northern Pacific Ocean are generally segregated by gender except when they are at Guadalupe Island, where it is hypothesised that they mate. The females then head offshore while they are pregnant (for about 15-16 months), returning to pupping sites along the coast of Mexico. The complete cycle for a female takes about two years. The evidence from the tracks generated by the tags is very compelling. Furthermore, working backwards using the gestation period for white sharks from when young of the year white sharks start to appear off the Mexican coast implies that mating takes place during the months when white sharks are known to aggregate at Guadalupe Island, which provides further support to the theory.
A white shark with a satellite tag
Domeier’s tagging methods have until recently involved the fairly invasive satellite tags that are bolted onto the sharks’ dorsal fins (see the Shark Men series for how this works, and some photos of a tagged shark here). The tags that provided the results of this study were actually affixed during an Ocearch expedition. The data obtained from such tags is remarkably detailed and will be invaluable in defining conservation objectives for this species.
Barbara Block’s team at Stanford, whose work I profiled yesterday, is responsible for a paper detailing a competing hypothesis, that white sharks in fact mate during their time offshore. This is science at work: competing ideas are not a bad thing at all, as they stimulate original thought and drive the process forward. The theory of the white shark’s life history that is best supported by the observations and experimental data is likely the most accurate one.
Read Domeier and Nasby-Lucas’s paper here. It’s quite short and very easy to understand. These are the kinds of results we can expect to see out of the tagging work done off the South African coastline in early 2012. Can’t wait!
I love maps (our home is full of them) and have more than a passing interest in sharks. I’ve fooled around with the meeting point of those two subjects during the course of a class I took called Maps and the Geospatial Revolution – you can see the results here. I was therefore delighted and intrigued when Mike (whose blog you should subscribe to – do it now!) posted a link to an ArcGIS map of shark incidents, worldwide.
His take on it was that it shows there is no correlation between shark bites on humans, and locations where sharks are fed or lured with food as part of eco-tourism, suggesting that (as the science also suggests) sharks are not turned into “man eaters” by nearby baited dive or cage diving operations.
Shark incidents worldwide
Check out the map here. Click on the Legend text in the left hand sidebar to see what the different coloured dots mean. As it stands the map is not terribly helpful for analysis because it’s hard to discern the different colours of the dots – the types of incidents range in severity. The dots are also clustered most around the most areas that are most heavily populated with sharks and water-using humans. This mostly tells you about population levels, and not so much about sharks. It’s impossible to see any kind of trend because the data is from 1982 to 2012. Conclusions (or hypotheses) such as Mike’s, that are time-independent, are quite appropriate, however.
There’s more information on the source data for the ocean map here (not for the shark incident data – I’d surmise that it came from here or here).
Randall Munroe of xkcd (all hail!) tackles another hypothetical question, and applies SCIENCE and some thought experiments to come up with an answer.
Supposing you did Drain the Oceans, and dumped the water on top of the Curiosity rover, how would Mars change as the water accumulated?
Last time he discussed draining the oceans, a plug was pulled at the bottom of the Mariana Trench. tl;dr the Netherlands took over the world. This time the water will be transported to Mars and poured into the Gale Crater. What will that do to the Martian landscape?
The Brunswick is an old wooden wreck from 1805 that lies in shallow water just outside Simon’s Town. I’ve taken some video footage on the wreck that also gives you an idea of what it looks like today. When Tony attended a talk on the Brunswick by an Honours student called Jake Harding, who has just completed a project on it, he learned that the rudder from the ship is currently on display in the courtyard of the Slave Lodge in Cape Town.
End-on view from the intact end of the rudder
I went to check it out, and it’s awesome! It gives a sense of how large the Brunswick was that I didn’t get from diving her, as the debris is quite low to the sand and much of it is buried.
The rudder of the Brunswick
The rudder was salvaged in 1967 by an American salvor, who discovered the copper clad rudder on the wreck site (at that stage unidentified). He required the assistance of the SA Navy to bring the rudder ashore, as it was so large. The rudder then lay on the dock in Simon’s Town for several days, during which time most of its copper cladding was stripped off. Some copper still remains on the rudder today, but it is in very poor condition and has the texture of cardboard – you could probably peel it off with your fingernails, if you were a bad person.
Pintle and copper cladding
The rudder would have been attached to the back of the ship – the stern – onto a part of the vessel called a sternpost (which is what it sounds like). There are hooks (called gudgeons) on the sternpost and pegs (called pintles) on the rudder that enable the rudder to be attached to the ship, and to move from side to side. There are three pintles visible on the rudder at the Slave Lodge, with one of them partly broken off. The rudder measures just over 4 metres by just under 2 metres, and is nearly 30 centimetres thick.
Holes bored by shipworm
One end of the rudder is jagged, and it is believed that originally the rudder was more than five metres long and had another 2-4 pintles. The work of shipworm, Teredo navalis, is evident at the jagged end, where the wood is full of thousands of tiny tunnels created by these creatures. These worms would have lunched on the rudder while it was still attached in the ocean. The cladding of ships’ hulls and rudders with copper was one way to prevent shipworm from damaging the wood while the vessel was still in use, thus prolonging their useful lifespans.
Red Sea Diver’s Guide, Volume 2: From Sharm el Sheikh to Hurghada – Shlomo & Roni Cohen
Red Sea Diver’s Guide, Volume 2: From Sharm el Sheikh to Hurghada
We’re off to the Red Sea in October, and on the advice of Ned Middleton, author of Shipwrecks from the Egyptian Red Sea, I got hold of this book (which was in itself quite a performance), as he rates it very highly among the proliferation of guidebooks about the area. I did a lot of searching on my own before capitulating and following Middleton’s advice, and was unimpressed by the number of books with lightweight overviews of the dive sites, pictures that were sourced from stock photo banks, and authors who haven’t even dived the areas in question.
If you plan to get hold of this book, Middleton’s review on Amazon.com highlights the errors it contains (some shipwrecks are named incorrectly, for example), which is important if you plan to dive the area. If you plan to dive the Red Sea and are looking for a reference book, this list contains some books to avoid, and this one lists some reputable guides.
The Cohens’ book was published in 1994, and at that stage, having dived in the Egyptian Red Sea for years, they could already observe deterioration in the reefs and a decline in the number of sharks and large fish. The nature of most dive sites, however, is such that their topography usually does not change appreciably with time, particularly in relatively sheltered waters. The book includes a number of maps, some of which are clever combinations of aerial photographs and semi-transparent overlays marking the pertinent landmarks and routes.
Both boat and shore dives are featured here, and with respect to the shore dives the Cohens’ layout and style reminded me very much of the excellent book we used when we visited Malta in 2011: Scuba Diving Malta – Gozo – Comino. There is enough information for a shore diver to be fairly self sufficient, although I would check the locations of hyperbaric chambers, filling stations, dive centres and other amenities as they may have changed (and increased in number) in the last 20 years. Live aboard diving was in its infancy in 1994, but was growing in popularity and the Cohens refer to it more than once in this volume.
Towards the back of the book there is a fish identification guide, which could be handy if you don’t have space to pack an additional fish ID book in your luggage. The book also came with a separate fold-out map of the northern Red Sea area.
You can get the book (probably) here. If you do look elsewhere for it, make sure you’re getting an English edition, as the German edition is much easier to find and looks practically identical. Caveat emptor!
