The Situation in Whitefish Bay
by Eric
Holst, Monday, March 28 at 9:14 PM
There could very well be a 12' deep
ridge of wind-rowed ice out at the edge of the ice field. Wind-rowed brash ice
can pile up even deeper than that in certain situations One such situation
would be exactly what we've got at the boundary between Whitefish Bay and the
larger expanse of Lake Superior: the edge of a thick ice field that's had all
winter to establish itself, which is then subjected to a long time period of
sustained large wave action beating against its outer edge, along with
sustained wind blowing from the open water against the ice toward the bracing
shoreline behind it.
That's not to say that there's somehow
12' of ice in the specific location where the up-bound ships have been lined up
and waiting. They intentionally chose to heave-to and wait in the part of the
ice field that's likely to remain "fast" (i.e. stable) plate ice
throughout the wind/wave event of the last few days. It's also not the
authorities' fault that the ships have been delayed, it's weather.
Copy & paste from an explanation I
wrote up elsewhere online earlier today, which might be preaching to the choir,
but might also provide some background:
Even today (March 28th) after winds
have dropped below gale force, relatively robust northwesterly winds are still
putting immense pressure on the field of ice in Whitefish Bay. Under those
conditions it's not easy or wise for ships to try to move up-bound / against
the wind / against the wind-driven pressure on the field of ice, especially if
those up-bound ships are traveling empty. The ice at the edge of the field,
after several days of strong on-shore (northwesterly) winds and waves like
we've seen in recent days, can be transformed from thick, wide, stable plates
of ice into "brash ice" - a chaotic jumble of huge chunks of ice that
have been tossed by waves, broken up, rolled around, re-fused, and pushed on
top of itself until the wind-rowed "ridge" of brash ice at the
fringes of the field can be stacked ten, twenty, or even thirty feet deep
-under- the water, like ice cubes stacking down into a glass of water as more
ice cubes get added to the top of the drink. If an empty ship, riding
relatively high in the water, tries to fight that brash ice while it's still
actively under wind pressure (in this case, northwest winds are blowing from
the direction that does the trick in Whitefish Bay), said empty ship could end
up with ice underneath her and get very, very stuck.
So what the up-bound ships and the
icebreakers have been doing over the past few days is very wisely waiting for
the winds to abate/change direction. They're waiting in a good spot - further
back/south from the edge of Whitefish Bay, where the ice is still more in big
stable plate form and easier/safer to hold position in. What seems to be
unfolding now is that several down-bound loaded ships have arrived near the
edge of the ice field. They have likely begun to encounter brash ice at the
edge of the field and proceeded until they can no longer make progress through
the ice. Where you see them now is not where they have gone to anchor, but
where they have come to a stop in the ice. Seems as though the icebreakers are
attempting to escort those down-bound ships through the ice first. There are a
number of advantages to that strategy given the current situation. Loaded ships
sit deeper in the water and have a better chance of handling thick, deep
accumulations of brash ice. These ships are traveling in the same direction the
wind is currently blowing, which might make it easier for them to fight their
way through the worst of the brash ice zones at the edge of the ice field. The
first two loaded/downbound ships also happen to be the two freighters with more
horsepower than any other ships on the Lakes - the Edwin H. Gott and Edgar B.
Speer. Those ship's horsepower make them some of the best candidates for
freighters that can handle heavy ice conditions. That, combined with the fact
that they're loaded and traveling with the winds, makes them a better
"bet" for icebreakers to work with first, while the northwest winds
and cold temperatures are still making conditions challenging.
A change in wind direction can make for
a world of difference in whether or not ships can navigate a field of ice,
especially in areas where previous winds and waves from the opposite direction
have formed thick ridges/zones of deeply-stacked brash ice chunks. Warmer
weather doesn't hurt either. At Whitefish Bay, both a warm-up in air temps. and
a change in winds to a nearly opposite direction from past few days' wind event
are forecast to begin developing on Tuesday. Sometimes within minutes or just a
few hours of the moment that shoreward wind pressure is removed from an ice
field, and winds either calm or switch to an off-shore directions, ships are
suddenly able to transit the recently formidable ice with relative ease,
especially when there are escort icebreakers around. If the wind switch indeed
unfolds tomorrow (Tuesday, March 29th) as forecast, the up-bound convoy would
likely be able to get moving.
Other
previously mentioned factors have also figured in the Coast Guard icebreakers'
decision-making process over the last few days. Unseasonably cold temperatures
and visibility reduction from wind-driven snow have also made conditions more
challenging and added to the stack of factors that led to the Coast Guard
having the up-bound convoy sit tight. Such situations are relatively common
early and late in the shipping season on the Great Lakes. What's new is that
we're gaining an increasingly to-the-minute, detailed, up-close view of such a
situation as it unfolds, and more and more people are gaining the ability to
ask questions about what's going on. With the proliferation of social media
information and opportunities for commentary and interaction comes an impetus
to spread good information and encourage interest from the general public based
on accurate information and positive engagement!
