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Day 65: Tides

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I wonder whether I’ll have those manly 6-pack abdominal muscles by the time I reach Alaska?  Back in high school, muscle definition (as well as $140 basketball shoes) somehow seemed very important at the time.  But though I spent long hours in the weight room for basketball training, I never did develop the coveted 6-pack.

I haven’t given much thought to my ab muscles for the past decade or so, but now, on my paddle up the Inside Passage, I’m using them more than ever.  Try this: grab ahold of your imaginary kayak paddle, arms bent, hands just a little wider than your shoulders.  Feel its rigidity; work it around in your hands until it feels comfortable.  Brace your knees under your desk for stability (if you’ve got one) and you’re ready to go.  Now start paddling, tracing out butterfly wings with the paddle blades, dipping first one, then the other, in the chilly water at your sides.  But hold on there — don’t paddle with your arms!  No no.  If I were propelling myself all this way just with my arm muscles, I surely would already have developed tendonitis or carpal tunnel, or would at the least be very, very sore — and I’m not even past Vancouver Island yet!  Don’t paddle with your arms; instead, concentrate on your core — use your abs to turn your torso back and forth, letting your shoulders do their own butterfly dance.  The ends of your paddle should dip into the water without hardly bending your arms at all.  Now that’s an efficient paddle stroke.  I’ll be doing about 1.5 million of these “paddle crunches” on my way to the Inian Islands, so I bet my adolescent dream of sexy abs will finally come true (even if they remain almost translucent for want of melanin, in true Alaskan style).  And if the cold air stimulates my beard to finally sprout — well, I reckon I’ll step onto the dock at the Hobbit Hole looking about like the dude from 300, brandishing a paddle instead of a spear.

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Sunrise over the Strait of Georgia. Getting up at 4:30 a.m. helps me beat the worst of the winds.

But even the strongest, most fearsome kayaker can’t get by on brawn alone here in the Inside Passage.  Tidal currents in these constricted waterways can run up to nearly 20 knots — paddling against that would tucker out even the 300 dude within half a mile.  Instead, you’ve got to play the tides to your advantage — and to do that, it helps to understand a bit about how tides work.

We all know that the moon is mainly responsible for tides on Earth.  The watery orb, orbiting the Earth every month and about 1% of Earth’s mass, exerts enough gravitational pull to distort our oceans rather dramatically.  The waters under the moon are drawn up towards it — this is the “lunar bulge.”  Picture an Earth with no continents — picture Waterworld, and you’ve made it to Dryland, one small island on a planetary ocean.  You sit on the beach, looking out for “smokers,” and watch the tide rise and fall.  What would happen?  As this watery world turns on its axis, the lunar bulge would follow under the moon, and once a day, Dryland would pass through the lunar bulge, and the tide would rise up and lap at your toes.

Kelp: a surefire indicator of which way the tidal current is moving.  In this case, dead against me.

Kelp: a surefire indicator of which way the tidal current is moving. In this case, dead against me.

But this isn’t the whole story, because most places on Earth have not one high tide per day, but two.  To understand that, we need to recognize that the moon doesn’t simply orbit around the Earth — in fact, the Earth and moon both orbit around their common center of mass.  In a sense, the Earth orbits the moon just as much as the other way around — the two are twin yo-yos connected by the same gravitational string — snip it, and they would hurtle off into space in opposite directions.  That’s centrifugal force (think of your last merry-go-round ride) and it works on our oceans too.  The upshot is that there isn’t just one lunar bulge, but two: the gravitational bulge we already met on the side facing the moon, and a second bulge on the side facing away from the moon, swirled outward by centrifugal force.  Spin your Waterworld globe again, and now Dryland is passing through two lunar bulges — hence two high and two low tides each day.

But that still isn’t the whole story, because the sun gets in on the act too.  Much bigger than the moon, the sun is also much much further away, and so exerts less than half the tidal force that the moon does.  Still, it changes everything: now, we have 4 bulges to reckon with: our two lunar bulges, and two smaller solar bulges.  The main effect of this new solar nuance is to dampen or amplify the tides, depending on the cosmic geometry.  If the Earth, moon, and sun are in an “L”, with Earth at the corner and the moon and sun out at the tips (as when the moon appears half full), the 4 bulges will be on 4 different “sides” of Earth, and these “neap” tides will be correspondingly moderate.  But when the Earth, moon, and sun are aligned in an “i”, as during full or new moons, now the lunar and solar bulges overlap each other, in effect creating two massive bulges and causing the huge “spring” tides (nothing to do with season) that can ebb out to reveal the most grotesque of intertidal creatures and flood right up into the trees.

Gotta stretch the legs after long cruising in the kayak...

Gotta stretch the legs after long cruising in the kayak…

But of course, this still isn’t the whole story, because this isn’t Waterworld (yet); there are continents — huge hunks of rock that interrupt the nice, tidy round-the-world march of the lunar and solar bulges.  When these bulges hit a continent, they can’t continue, and that wave of water (for tides are waves) gets deflected, spinning off along the continent according to the confusing laws of physics on a rotating sphere, spiraling in the ocean basins until they begin interacting with the next bulge marching through.  Put it all together (and many other nuances that I’ll spare you and spare myself), and it’s no wonder it took us a long time to figure out all the details.  Isaac Newton had gotten the broad strokes right, and Lord Kelvin had built the first English tide predicting machine back in the 1880s.  Tides, unlike weather, are predictable, but as with so many of our greatest discoveries, this one was only finally made in order to kill people.

As the Allies prepared to invade Nazi-occupied France in 1944, in what would become the historic D-Day attack on the beach at Normandy, they had to know the tides with certainty — whether the tide was in or out would mean the difference between a successful storm vs. beaching the boats 100 yards further out and slogging through mudflats under heavy machine gun fire.  Arthur Doodson was the man who finally worked out the mathematics, using 11 pairs of harmonic constants and incorporating dozens of tidal components.  The flooding tide (not yet high — a compromise between the demands of the Air Force and Navy) carried the Allies up the beach and to victory.  One could even say it turned the tide of the war.

I took shelter from the wind on a miles-long log raft across from the pulp mill at Nanaimo Bay.

I took shelter from the wind on a miles-long log raft across from the pulp mill at Nanaimo Bay.

One last thing about tides: why are they so goddamn big and powerful here on the Inside Passage, with all its bays and inlets and narrow straits?  Turns out that it’s all about resonance — like the way the high E string of a guitar vibrates sympathetically when you pluck the low one.  Bear with me for one last analogy, because this is the best way it was ever explained to me.  Imagine walking across a room with a glass of water — chances are, you won’t spill, right?  We do it all the time.  But now imagine walking across the room with a washbasin full of water — try as you might, it’s probably going to slosh out all over your jeans and carpet — and the reason is resonance.  Every vessel, depending on its size, has a natural “period” over which it “likes” to fluctuate.  The washbasin, being about 2 feet across, resonates with the “forcing” — in this case, your walking stride which is about the same size.  With every step, you’re amplifying the wave that’s building inside, until it soaks you.  Out in the ocean, the “forcing” has a period of 12 hours or so (from one high tide to the next) and it turns out that bays like Glacier Bay where I grew up, or the infamous Bay of Fundy, are the right size that they “like” to oscillate every 12 hours — they resonate — and the result is a ship-tossing tidal maelstrom.  This effect is felt to a greater or lesser extent all up and down the crenelated coastline of the Inside Passage maze.  No surprise — it’s felt especially strongly at the Inian Islands.  In fact, North and South Inian Passes, on either side of the archipelago, are world-class hotspots in tidal power potential (thankfully this won’t be developed anytime soon, given there’s nobody around demanding that power, and given these lands are protected Wilderness).  Here’s a clip, if you haven’t seen it, of the nourishing tide flooding into Hobbit Hole cove.  What a dynamic place!

So you want to play the tides right up here in the Inside Passage.  Will you come back from a beer in town and find your boat safely tied above the water, or floating out to sea?  Will you wake up and find the water close at hand, or a quarter mile down a rocky slippery shore, a nasty schlep for your boat and gear?  Will paddling the next strait be a sweat-dripping siege against the current, or a pleasant river ride, finger interlaced above your head as you admire the mountains?  I definitely have to play the tides right tomorrow, as I head for dangerous Seymour Narrows, a tight constriction between islands where water doesn’t flow through, it explodes, clawing at the tight channel walls like a caged beast.  Seymour Narrows is a river — only addled, schizophrenic — it can never decide which way it wants to flow.  It bursts in on the flood, and then there’s this instant of peace — slack water — it’s the weightlessness you feel at the apex on a playground swing, before you plunge back the other way.  Luckily, I’ll be hitting Seymour at half moon (that means the smaller neap tides) and I’m watching it real careful.  I’ll get through just fine.

Sweet Campsite.

Sweet Campsite.

For all the tidal madness of the Inside Passage, heretofore I’ve been much more concerned about winds.  I’ve been battling a headwind for 5 straight days, and I’m plum exhausted.  During my hike, the wind really wasn’t a big deal — sure, I complained about it in a couple of posts, but it never stopped me from getting where I wanted to go.  Wherever your beach is, go there for a minute: see the shells underfoot and hear the surf — and now feel a stiff breeze on your face — maybe 20 knots.  It’s enough to make your coat flap, and you might put your sunglasses on to protect against the odd windblown bug or salt spray.  But your feet are planted on the solid sand, and you easily set off walking.  But now imagine that the wind sets the entire beach into motion, like a giant treadmill, and unless you get walking you’re pulled inexorably backwards.  That’s what it’s like out here on the water… the wind itself is one thing, but then I look to the side and the whole ocean is surging back towards Port Angeles.

After doing battle each day, I turn on my VHF radio and hear the metallic voice: “Extended marine forecast for Pacific waters, issued by Environment Canada at 0400 … Fog implies visibility less than one mile … Strait of Georgia north of Nanaimo:
“Wednesday … Winds northwest one-zero to two-zero knots, strengthening to northwest one-five to two-five knots in the afternoon …
“Thursday … Winds northwest one-zero to two-zero knots, strengthening to northwest one-five to two-five knots in the afternoon …
“Friday … Winds northwest one-zero to two-zero knots, strengthening to northwest one-five to two-five knots in the afternoon.”

Sigh.  It’s a little disheartening.  Yet I’m still making headway, and it gives me confidence that when things change, when the winds and tides are right, I’ll be straight cruising.

 

 

One Comment Post a comment
  1. Mike Rivers #

    HI Zach,
    Well I’m finally headed out of Waldport Monday 7/21, headed towards Gustavus via ferry from Bellingham, with a layover in Juneau for a family art show opening. I set up a Spotwalla for me at:

    https://spotwalla.com/tripViewer.php?id=aa5f53caca87ccf82

    I’ll be tracking you from my trip and maybe I’ll be able to spot you and wave from the Columbia and/or see you in port along the way!

    Paddle safely and watch the big wake from those ferries!

    Mike Rivers

    July 19, 2014

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