This bloke, at Coogee last Sunday, is about to experience the Ekman transport effect.
In this issue...
- Swims this weekend
- It's all Ekman's fault... Cold water on the coast
- Win a trip to Fiji
- Murray Rose memorabilia for auction
- new oceanswimsafaris - Costa Brava in the South Pacific
- oceanswimsafaris - Costa Brava in Catalonia/Spain, San Sebastián
- new oceanswimsafari... But where?
- More changes this season
- Working with our swim calendar
- Swims open to online entry
- Saturday, Dec 2 - North Curl Curl e (NSW), Mentone (Vic)
- Sunday, Dec 3 - Bondi-Bronte (NSW), West Lakes, Seacliff (SA), Nelson (NZ)
Cold water upwelling on Australian coastlines
This story was published on the website of the Bureau of Meteorology on February, 15, 2017. Thank you to Steve Weller (@EssRon) for pointing it out.
Have you ever gone to the beach to find the water much colder than the day before? A range of factors influence sea surface temperatures in coastal waters. This article looks at the 'Ekman transport' effect—a wind-driven process that brings colder water to the coastline.
The continental shelf in Oceania. That's the green bit. (Image from National Geographic Society)
What is Ekman transport?
Ekman transport is the movement of seawater that occurs under certain wind conditions. It is named after Swedish oceanographer Vagn Walfrid Ekman, who first described the phenomenon in 1902.
How does it work?
Sustained winds in a consistent direction over the ocean move the top layer (about 30 metres depth) of seawater. In the southern hemisphere, the seawater layer moves to the left of the wind direction, due to the Earth's rotation (known as the Coriolis effect).
As the top layer of water is moved by the wind, it needs to be replaced. If the coast is to the right of the wind direction, and the winds persist for more than a day, an 'upwelling' process draws up colder and more nutrient-rich water from the depths of the ocean to the surface. The longer the winds persist, and the longer the stretch of coastline that experiences a similar wind direction, the colder the water brought to the surface. This upwelled water can last for days (or longer) until wind conditions change and the seawater mixes.
The reverse process (downwelling) can also occur, bringing warmer water towards the coast from boundary currents such as the East Australian Current or Leeuwin Current.
Left: Winds blowing along the east coast of Australia can lead to upwelling of colder water to the surface.
Where does it occur?
Upwelling is more likely along certain parts of the Australian coastline, particularly along New South Wales, southeast Queensland and the Bonney Coast (South Australia).
An important factor is the width of the continental shelf, that is the landmass that extends with a shallow gradient from the continent underneath the ocean. Upwelling occurs when the continental shelf is narrow, i.e. where the sea becomes very deep relatively close to the shore, as the deeper water requires less time and energy to reach the coastline. This is why it's observed along the southeast Queensland and far north Queensland coasts, but typically not within the Great Barrier Reef lagoon.
Headlands and bays along the coastline may also vary the effects from beach to beach.
Your location will determine the wind direction required for the upwelling to occur. If you look out to sea from the shore, the wind needs to be consistently blowing from left to right. This means that northerly or northeasterly winds are required along most of the east coast, but southeasterly winds in the eastern Great Australian Bight.
What will you observe?
In an upwelling event, swimmers may notice that water temperatures at the beach get colder from one day to the next. In some cases this has led to hospitalisation for hypothermia.
While swimmers may find this uncomfortable or hazardous, those who enjoy fishing could have cause to celebrate. The cold water drawn up from the ocean floor is typically richer in nutrients and can boost fish numbers.
From an ecological perspective, upwelling of nutrient-rich water is important for attracting and nurturing marine life, including whales.
What other factors influence coastal sea surface temperatures?
A range of other factors influence the water temperature for swimming and other marine activities:
- Geographic location (tropical waters vs Southern Ocean)
- Time of year
- Strength and direction of ocean basin currents
- Climate patterns (such as El Niño/La Niña)
- Winds and tides
- Water depth
- River run-off, rainfall or snow melt
- Keep an eye out for sustained winds forecast and observed along the coastline.
- Monitor forecasts for sea surface temperatures and currents.
This is all very interesting stuff. But it begs a few questions...
1) We get nor'-easters all summer. Why does the Ekman effect not work thorughout the entire period?
2) Is the intensity of the nor'-easter over an extended period the relevant factor, eg Black nor'-easters over several days, say?
3) Why does the cold water disappear often as quickly as it emerges, without any discernible change in wind patterns?
You can win a trip for two to Fiji to take part in the Mana Fiji SwimFest in October, 2018, just by entering the Cole Classic @ Manly... Click here
December 7 is the date of the auction of Murray Rose's memorabilia, by the Leonard Joel Auction House in Melbourne. Jodi Rose tells us, "I’ve always kept Murray's memorabilia in excellent condition – robes, tracksuits, blazers, towels, swim suits, from the 1956 and 1960 Olympic games. Plus, lots of official programs, pins, stamps, big and little trophies, etc. It feels right to allow many of these beautiful items to go to Australian collectors (or museums) who will preserve them into the future. Just storing in the back of a closet or storeroom creates deterioration which is not a good thing."
You can check the collection, part of an auction of diverse sporting memorabilia, in the Joel catalogue... Click here
We've said this before, and we'll say it again now: us baby boomers grew up with Murray as our role model: he was not just one of the world's outstanding athletes of his day; he was more. Murray was the ideal Strã'an young bloke, wholesome, clean, nice to his mum and dad; the perfect role model... Yeah, yeah, we've heard all this about so many sporting role models, and look where they end up... So it was refreshing and reassuring to find, when we met Murray later in life, and we became friends, that he actually was that person. Such a good, decent bloke. He lived up to all those ideals, not because he tried, but because it was in him. We rank Murray up there almost with our late dad, Rotten ol' Herbie.
Murray's legacy lives on: this week (last night, Tuesday), we attended the launch at the Boyo Charlton Pool of the 10th Murray Rose Malabar Magic. It's on February 18, raising funds for Murray's favourite charity, The Rainbow Club... Click here
Murray's medals are owned now by Jodi and Murray's son, Trevor, and housed in the Sporting Hall of Fame at the MCG.
Pic of Murray above by Jacky Ghossein, The Sydney Morning Herald.
We're enjoying a good response to our first oceanswimsafari to New Zealand, to the remote Coromandel Peninsula, in early April. It's basically a long weekend -- Thursday-Monday -- using an anchor event, the Cathedral Cove Swim at Hahei (see pic at right). We'll do informal swims along this stunning coast -- which reminds us very much of Spain/Catalonia's Costa Brava, with its towering cliffs with homes perched precariously on their distant peaks -- enjoy a sea kayak tour of the surrounding bays and islands, visit the thermal springs at Hot Water Beach, where you can make your own bath by digging down into the sand, and a whole lot more water-type activities surrounding it.
We visited the Coromandel earlier this year to try out this tour. It’s a spectacular location, very clear water, lots of interesting sea life, and one of the most stunning coastlines in the South Pacific. The Coromandel is a remote, unspoilt finger of land to the east of Auckland. It's almost a wilderness, with very little population and beautiful countryside.
Our Coromandel oceanswimsafari long weekend dates are April 5-9, the week after Easter. We'll meet at Auckland Airport and transfer to the Coromandel from there. Packages are on oceanswimsafaris now. This one will be popular.
More info and to book… Click here
We're about to release packages for our Spanish/Catalan/Basque oceanswimsafaris in 2018, and our Yasawas dates in Fiji.
We tell you about our inaugural NZ Coromandel oceanswimsafari in April 2018 above. We also have online now our packages for Sulawesi in Indonesia and to swim with whales in Tonga in July/August. We're already taking bookings for these oceanswimsafaris so, if you're interested, get onto us quick and smart... Click here
We have pretty much finalised our packages to San Sebastián in Spain's Basque country, in August, 2018, and for our Costa Brava oceanswimsafari, also in Spain (or maybe it will be Catalonia by then), in September 2018. When confirmed, we'll first let know the punters who have already lined up for these oceanswimsasfaris, then we'll post them online on oceanswimsafaris.com. We're also finalising a package to swim/sail in Greece's Northern Sporades later in September.
Ditto our Yasawas oceanswimsafaris. Mana Fiji will be in the last full week of October, 2018, and we'll take an oceanswimsafari to Fiji's Yasawas the week prior to Mana.
Another taste of our new oceanswimsafari, teasing you just that little bit more... It's a particularly exotic location and with a very special main attraction. We're very excited about it. Stunning water, and the healthiest reef we've ever swum over.
This one will be in late June/early July, 2018. Just a hint: it's somewhere in that sprawling myriad of islands that make up the South-East Asia archipelagoes. That's it above, right here, too. This pic also by Glistening Dave (@glistenrr)
Yet another change to the calendar this season...
The Head2Head Swim at Black Head will not run this season, yet another casualty of an organising club's need to find a long term event organiser. Black Head was scheduled to run on Sunday, January 14. Let's hope it returns in 2019.
oceanswims.com has run complete event calendars for Australia and New Zealand pretty much since we got going at the beginning of the 21st century.
For complete event listings, check our calendar under Swims at the top of each and every page on oceanswims.com. You can search the calendar by state, country or region (eg Sydney North Side, Sydney Eastern Suburbs, Victoria Surf Coast, NZ South Island, etc), or even by type of swim (Lake, Estuary, Surf Beach, etc), by type of water (Salt, Fresh), and in many other ways.
We list Featured Swims down the right hand side of pretty well every page on oceanswims.com. These are events that work with us to gain extre prominence for their swim. Generally, Featured Swims also offer online entry, but occasionally you still can enter online to events that don't take the Featured Swim status, so if you don't see the swim you're looking for on Featured Swims, check our complete calendar, too.
Fine ocean swims calendar in NZ
For NZ swims, there is a new website run by former fine ocean swimmers tallies winner Mike Cochrane which is a simple calendar of swim events. We'll list swims on oceanswims.com as well, but you also can check out Mike's calendar for a comprehensive list of NZ swims... Click here
Meanwhile, many new season swims are open for entry now on oceanswims.com…
- Dec 2 - North Curl Curl (NSW, 2km + Biathlon)
- Dec 9 - Coogee-Bondi (NSW, 4.5km)
- Dec 10 - Bilgola (NSW, 1.5km, 800m)
- Dec 28 (Thurs) - Glenelg (SA, 5km, 2km, 1km)
- Jan 7 - Gerringong (NSW, 1.8km)
- Jan 7 - Newport (NSW, 2km, 800m, 400m)
- Jan 7 - Yamba (NSW, 2km, 700m)
- Jan 14 - Avalon (NSW, 2.5km, 1.5km, 1km)
- Jan 14 - North Bondi (NSW, 2km, 1km)
- Jan 26 (Strã'a Day) - Newcastle Harbour (700m, 1.4km)
- Jan 27 - Nobbys-Newcastle (NSW) (2km) - Note new date, rescheduled from Dec 9
- Jan 28 - Palm-Whale (The Big Swim) (NSW, 2.5km, 1km)
- Feb 4 - South Maroubra (NSW, 2.2km, 1km)
- Feb 11 - North Bondi (NSW, 2km, 1km)
- Feb 18 - Malabar (NSW, 2.5km, 1km)
- Feb 25 - Bondi (NSW, 2km, 1km)
- Feb 25 - Wollongong (NSW, 2km, 800m, 400m)
- Mar 12 (Mon) - Port Noarlunga (SA, 2.5km, 1.5km)
- April 8 - Coogee (NSW, 800m, 1km, 2.4km)
Coming soon... Glenelg (SA, Dec 28), North Bondi (NSW, 1km, 2km, Jan 14, Feb 11), Bondi (NSW, 1km, 2km, 4km Sand Run), Freshwater (NSW, Mar 4)
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