by hausen » March 26, 2022, 10:39 pm
Guest wrote:6 boats stopped all day Saturday in Whitefish Bay. Is that due to heavy ice or bad weather?
It could be said to be both! Or, put another way, ice
is weather. But in the spirit of the way the question was asked:
It's a combination of wind acting on the ice in Whitefish Bay, waves acting on the edge of the ice field at the opening of Whitefish Bay to greater Lake Superior, and unseasonably cold air and large wind-driven waves beyond the ice on the open lake.
As Roger alluded to above, when wind puts pressure on an ice field (i.e. when it blows the ice toward a shoreline, especially a narrowing or encircling bay), it can make it very difficult for a ship to move through, even if that ice field might otherwise be relatively easily negotiable on a day with calm winds or winds blowing in a different direction. The line of ships currently waiting to exit Whitefish Bay upbound might not actually be "stuck" so much as they know that trying to fight the ice field while it's under so much pressure from wind is probably not going to yield much success. They seem confident that the location where they're stopped, in thick plate ice that's 'fast' (i.e. strongly attached to shorelines on all sides), is one where the ice field isn't likely to be able to start moving and bring the ships with it into dangerously shallow water or dangerous proximity to shore.
Out at the ice front, large waves being driven in from the northwest might be breaking up the edge of the plate ice that formed and thickened in Whitefish Bay over the winter. It's common in such situations for the waves to build a "windrow" or series of windrows at the ice edge: a zone of densely-packed large chunks of broken, rolled, churned, and re-fused ice that can pile up into thick ridges several feet taller than the rest of the ice field, and even more importantly could have been pushed into a dense jumble of ice chunks that can be stacked dozens of feet (several meters)
down into the water. Windrowed ice can be difficult for even heavy icebreakers to break through, especially when under active wind / wave pressure pushing it against the rest of the ice field shoreward, so even if the rest of the plate ice in Whitefish Bay was something the ships could negotiate, trying to bust out through a windrow or two while it's still being built/under wind and wave pressure might not be the best idea either.
Additionally, if the ships currently waiting in Whitefish Bay were somehow able to make it to open water this weekend, unseasonably cold air temperatures and northwesterly gale-driven waves would make it difficult to exit Whitefish Bay and find a good weather course out across Lake Superior without accumulating significant freezing spray, which is typically something ships try to avoid.
[quote="Guest"]6 boats stopped all day Saturday in Whitefish Bay. Is that due to heavy ice or bad weather?[/quote]
It could be said to be both! Or, put another way, ice [i]is[/i] weather. But in the spirit of the way the question was asked:
It's a combination of wind acting on the ice in Whitefish Bay, waves acting on the edge of the ice field at the opening of Whitefish Bay to greater Lake Superior, and unseasonably cold air and large wind-driven waves beyond the ice on the open lake.
As Roger alluded to above, when wind puts pressure on an ice field (i.e. when it blows the ice toward a shoreline, especially a narrowing or encircling bay), it can make it very difficult for a ship to move through, even if that ice field might otherwise be relatively easily negotiable on a day with calm winds or winds blowing in a different direction. The line of ships currently waiting to exit Whitefish Bay upbound might not actually be "stuck" so much as they know that trying to fight the ice field while it's under so much pressure from wind is probably not going to yield much success. They seem confident that the location where they're stopped, in thick plate ice that's 'fast' (i.e. strongly attached to shorelines on all sides), is one where the ice field isn't likely to be able to start moving and bring the ships with it into dangerously shallow water or dangerous proximity to shore.
Out at the ice front, large waves being driven in from the northwest might be breaking up the edge of the plate ice that formed and thickened in Whitefish Bay over the winter. It's common in such situations for the waves to build a "windrow" or series of windrows at the ice edge: a zone of densely-packed large chunks of broken, rolled, churned, and re-fused ice that can pile up into thick ridges several feet taller than the rest of the ice field, and even more importantly could have been pushed into a dense jumble of ice chunks that can be stacked dozens of feet (several meters) [i]down[/i] into the water. Windrowed ice can be difficult for even heavy icebreakers to break through, especially when under active wind / wave pressure pushing it against the rest of the ice field shoreward, so even if the rest of the plate ice in Whitefish Bay was something the ships could negotiate, trying to bust out through a windrow or two while it's still being built/under wind and wave pressure might not be the best idea either.
Additionally, if the ships currently waiting in Whitefish Bay were somehow able to make it to open water this weekend, unseasonably cold air temperatures and northwesterly gale-driven waves would make it difficult to exit Whitefish Bay and find a good weather course out across Lake Superior without accumulating significant freezing spray, which is typically something ships try to avoid.