The Meteo-Tsunami of June 10th

154

Submitted by the Sources of
Knowledge Forum

At 4PM on Wednesday, the 10th of June, a large meteo-tsunami wave arrived on the west coast of the Northern Bruce Peninsula, causing the water levels to rise and fall over several hours. It caused significant damage in Baptist Harbour and probably elsewhere. 

The Sources of Knowledge Forum operates a network of three high-resolution water level recorders, located in Tobermory outer harbour, Baptist Harbour and in the lee of Devil Island east of Russell Island. This network captured an unusually detailed description of this uncommon event, which will be available shortly as an article on the Sources of Knowledge website. 

The event arrived simultaneously with a storm front which moved from southwest to northeast at about 100 km/hr. A useful mental image is to think of it as a bow wave to the storm’s boat, and the water level oscillations that continued for several hours after the storm passed as the wake of that storm/boat. The water level at Devil Island, recorded every minute from noon to midnight on the 10th, is shown in the accompanying chart, along with the abrupt barometric pressure variations recorded at Tobermory as the storm passed.

The water level at Devil Island, recorded every minute from noon to midnight on June 10th, along with the abrupt barometric pressure variations recorded at Tobermory as the storm passed.

This “bow wave”, as it arrived at Devil Island from the open lake, takes the form of a 15 cm rise in lake level over 4 minutes, followed by a 30 cm drop over the next 15 minutes. A very similar pattern was recorded 5 minutes later in Tobermory harbour, and an hour later in diminished form at Parry Sound. This slow change in water level might go unnoticed to someone on the shore but it represents a 30cm high wave, moving to the northwest at 100 km/hr, with peak to trough separation distance (semi-wavelength) of tens of kilometres. That is a lot of water being lifted up and then dropped down! 

At Baptist Harbour, which has a natural resonance of 16 minutes, the bow wave acted like the clapper to a bell and set the harbour into water level oscillations – a seiche – reaching almost 2 metres at one point. 

We would welcome any observations of unusual water level activity or actual damage occurring on our coastline in the eight hours following the 4PM onset on June 10. Please send them as emails to info@sourcesofknowledge.ca. 

Water level variations from noon to midnight at Devil Island (heavy trace) compared to barometric pressure variations (light trace) measured in Tobermory Harbour. Water level scale is on the left, pressure scale on the right. Water levels are plotted relative to a baseline of zero prior to the arrival of the storm.