Going with the flow: Understanding tides For the creatures that live near the ocean shores, the rhythm of the tides is an important part of life. Just like the rising and setting of the sun, or the cycle of the seasons, the tides dictate what they do, and when, and how.
For humans here in Tofino and Ucluelet, this is no different: Paying attention to the tides (something that comes naturally once you have lived here a while) makes life easier.
Tides are caused by the gravitational pull of both the Sun and the Moon on our planet. When the Sun and Moon are in line (either at full moon, when the Earth is lined up between the Sun and the Moon, or at new moon, when the Moon is between us and the Sun) their gravitational forces are pulling in the same direction, and the tides are strongest.
The gravitational force does not only pull on the oceans; it also pulls on the atmosphere, and on the planet itself. The pull on the oceans can cause deformation of the oceans’ surfaces of up to tens of metres (the height difference between high and low tide). The atmosphere is fluid, too, but since it is much thinner than the ocean the deformation up there can be several kilometres—but we never see that from down here.
Likewise, the solid planet is much stiffer. Deformation from an earth tide can be up to several centimetres—something that scientists can measure, but that we would never notice ourselves.
Here on the west coast we get two high tides, and two low tides each day. The Earth rotates once on its axis in approximately 24 hours. But the Moon is actually orbiting around the Earth in the same direction as the Earth is rotating—so from down here it seems that the Moon is moving more slowly. That is why sunrise is roughly at the same time every day (every 24 hours) but moonrise gets 50 minutes later every day. And, since the tides are most strongly influenced by the Moon (since it is closer) the tides also become 50 minutes later each day.
So, if you pay attention to the cycles of the Moon, here on the west coast you barely need to refer to a tide table.
The greatest tidal range is around the full and new moon, with the high tides around noon and midnight, and the difference between high and low of 10 or even 12 metres. The smallest tides are at the half-moons, with the lows around noon and midnight, and a difference of only a few metres between high and low tide.
All of that moving water generates currents. At high and low tide, the water is not moving and so there will not be current (this is true only for the open coast—but not for places with lots of inlets and islands, e.g. the east side of Vancouver Island). The strongest currents occur between a big high and a big low—for example, mid-morning or mid-afternoon around the full moon.
Paying attention to the tides when you visit Tofino and Ucluelet helps you have your best visitor experience. Here are a few examples of how you can use the tides:
Exploring the shorelines is best done at low tide. For example, at Chestermans Beach, you can only walk out to Frank Island at low tide. And you want to make sure that you don’t walk out there on a rising tide, because you might find yourself trapped there for 6 hours waiting for the tide to fall!
Examining tide pools also can only be done when the tide is out. Creatures that live in the pounding surf for half of the day are suddenly left high and dry, clinging to rocks, or waiting out the tide in tranquil rock pools.
Bearwatching trips are best done on a morning low tide (so just after the full or new moon) when bears are most active, foraging for crabs and barnacles along the shoreline.
Going with the flow: Understanding tides
Surf spots change hourly, both as the water depth changes and as the current of the incoming or outgoing tide influences how the waves break. Each spot is different, though—check with a local surf spot about what tide is best to surf your location.
Fish also move according to the tides and the current, so a fishing spot that seems dead might be just hopping with fish a few hours later.
Intelligent sea kayakers use the tide tables to predict current directions and strengths in their route planning, to make their paddling easier. The most extreme tidal range of the year is on the solstice full and new moons.
This little video showcases one of my favourite places to explore on an extreme low tide:
- Text, photos & video by Jacqueline Windh©
