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August 23rd, 2009 – Gjoa Haven, Nunavut
by Zeta Strickland
Gjoa Haven, Nunavut (August 23): Today’s Crew Log comes from onboard educator Zeta Strickland, who’s discovered more about ice than she ever thought she would as Ocean Watch continues its way through the Northwest Passage:
Ice.
I expected I would learn a lot when I joined the Ocean Watch crew. As predicted, I’ve learned a fair bit of sailing terminology (I can now tell port from starboard), and I can now locate on a chart and correctly pronounce the names of many arctic villages and hamlets from Tuktoyaktuk to Gjoa (“Joe-ah”). But what I didn’t realize was how much I would learn about ice, and what I didn’t appreciate was how much there even was to know about ice.
Ice is the main item that determines how a trip in the Arctic will proceed. The ice dictates when you move and how far you go. This can be quite challenging because ice is also moving and changing, some days with astonishing speed. More than one would-be explorer of days gone by, who watched their boat be crushed by the ice, discovered it the hard way: Ice is serious stuff.
As Ocean Watch enters the next critical point of ice blockage along our route, just to the north in a body of water called Larsen Sound, all on board are watching the daily ice charts with increasing interest. As we’re not the sort to keep all the fun to ourselves, we’d like to invite you to take a look at the ice charts along with us, and play along at home in a little game we like to call: “Should We Go Yet?”
To begin, click on the attached ice chart from the Canadian Ice Service. These charts are put together each day from satellite data. So, do you see the chart? The white areas are land, or water outside the view of the satellite. The colored areas represent different concentrations of ice. On Sunday, we were positioned in Gjoa Haven, on the southeast side of King William Island, a round-ish island situated between 95W and 100W Longitude, and just below 70N Latitude. (Longitude lines are those vertical lines running north and south on the chart, latitude lines run horizontally, from east to west.) See the island? Great. The Boothia Peninsula is that large column of land to the east of our island, pretty much in the middle of the page. The water to the west of Boothia is called Larsen Sound.
Now that we have the geography, let’s look at all the colors. Each color represents a concentration of sea ice, and the key at the bottom of the page explains what each color means. Blue water is covered by less than 1/10 ice (10%), green areas are covered by 1/10-3/10. Yellow areas are covered by 4/10-6/10; orange and red are covered by 7-8/10 and 9-10/10 respectively. But there is more to this story than just the colors. Notice each color region on the map has letters; additional information can be learned about each region of ice by looking at the corresponding oval, or “egg,” at the bottom of the page – each letter on the map corresponds to an egg at the bottom.
Find the yellow region labeled on the map with the letter “F,” and the egg below labeled F. On the egg, each row and each column explains characteristics of that section of ice. The top number in the egg gives a more precise value for the percentage of ice than the color code. For example, the letter F section is yellow, meaning it is 4/10-6/10 of ice. Looking at the F egg below we see the actual percentage of ice in that area is 6, meaning 6/10 ice; that area is covered by 6/10 (60%) ice.
The second row of the egg describes how much of the ice in that area is of each type; our egg lettered F in the second row shows a 1 and 5, meaning that area is 1/10 one ice type and 5/10 of a different ice type. (Notice that 1+5 = 6, the number at the top of the egg.) This doesn’t actually tell us what types are present, so rows 3 and 4 further explain the type and floe size of ice present, and the numbers match up in columns.
Confused? I know, but stay with me a moment: in this area, 1/10 (row 2) of the ice is type 7 (row 3) and size 4 (row 4). (See how that stayed in the columns?) Move to the next column – in this yellow section 5/10 of the ice is type “4″ and size 4. To figure out what type 7 and 4 represent, as well as what size 4 actually means, you have to look to descriptive keys online that explain it all.
This can get complicated, but generally speaking, the bigger the number, the thicker (or wider) the ice. Numbers followed by dots are even thicker. So a 7 is thicker ice than a 3, but a “4.” is thicker than a 7 (without the period). Thickness, generally speaking, correlates with the age of ice: Ice formed this year tends to be thinner than ice that is several years old. In our case, letter F, the 7 means that ice is 30-70 cm thick, and the “4.” means that ice is more than 120 cm thick – the 4’s in the bottom row mean the ice is composed of medium-sized floes, 100m -500m across.
That explains the whole egg, but honestly, we generally are most interested in the top number, which is percentage of ice is that area. Simply put, Ocean Watch and her crew will carefully proceed through green areas, cautiously go through short stretches of yellow when necessary, and do everything we can to stay clear of the orange and red. And we always keep an eye out for old ice and icebergs. Icebergs we haven’t seen yet, but we will once we get closer to Greenland. Icebergs and old ice (ice more than two years old) are mainly made of pure water – there is very little salt present – which means the ice is hard! (We don’t want to hit that!)
We also look at the other symbols that may be present on the chart. At the north edge of both ice regions (72N), there is a south-pointing arrow with a 5 and a 6; these tell us that the north edge of that ice is moving south about 5 or 6 nautical miles a day. (A nautical mile is just a bit longer than a land mile.) The curly lines that look like a sideways “S” means there could be strips and patches of ice in areas that otherwise are fairly clear. Without a doubt, however, our absolute favorite symbol is three little horizontal lines on top of each other: This denotes ice-free water. Yes, we like that one quite a bit.
So now you know the basics of reading an ice chart. For the next several days as we head north you can download the most recent ice chart and follow along. Go here. When the map loads, select Western Arctic. Scroll down to the “Daily Concentration Maps” (in color), and select “Queen Maud Gulf” (either the pdf or gif). That’s our area. Take a look, and follow along at home. Should we stay near the west coast of the Boothia Peninsula, or go farther west? What’s our best path, and what kind of ice do you think we’ll go through? Teachers, there is a lesson all about the ice charts and these ice eggs here (PDF), and many more lessons about sea ice here.
And if you get any inside information on sea ice conditions, let us know. With fair winds and a little luck, we’ll see you in a few days on the north side.
- Zeta Strickland
This crew log submitted by Iridium OpenPort and Stratos
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(August 6): Today’s special crew log is a two-part collaboration from Ocean Watch skipper Mark Schrader and our on-board educator, Zeta Strickland of the Pacific Science Center. Though a stiff northwesterly wind filled in overnight, Ocean Watch is resting comfortably at anchor in the protected confines of Booth Island, and for the moment the crew has chosen discretion over valor and decided to take a lay day while the weather blows through. While we’re waiting, here are two reports, one by the captain on the current status of the voyage, and the other from Zeta in the third installment of her Teacher’s Log.














