Icebergs - a major threat to navigation
Once again, I would like to thank Dr. Billy R. Caldwell, Ph.D, a prominent geologist and author of the popular book, "Geology in the Bible" (bcgeology@sbcglobal.net), for providing me with a wealth of knowledge on icebergs. If one would like to talk with Dr. Caldwell, his phone number is (817) 246-5477. His book has been published by Exposure Publishing. I found it a thoroughly interesting read, even for a non-religious person.
Icebergs are a mass of ice that has become detached, or calved, from the edge of an ice sheet or glacier and is floating on the ocean. Because ice is slightly less dense than water, about one-ninth of the total mass of a berg projects above the water.
Icebergs differ from other ocean ices. Sea ice is formed directly from the freezing of ocean water. Pack ice is tightly packed fragments of sea ice. Ice floes are small, floating ice fragments that separate from pack ice. Fast ice is ice attached to a shore.
Icebergs are mostly white because the ice is full of tiny air bubbles. The bubble surfaces reflect white light giving the iceberg an overall white appearance. Ice that is bubble-free has a bluish tint which is due to the same light phenomenon that tints the sky.
The bluish streaks of clear, bubble free ice often seen in icebergs results from the refreezing of meltwater which fills crevasses formed in the glacier as it creeps over land. The ice is blue because of the natural light-scattering characteristics of pure ice. Occasionally, airborne dust or dirt eroded from land ends up on the glacier surface eventually forming a noticeable darkened brown or black layer (in any orientation) within the ice of a floating iceberg.
Greenland is the source of most of the icebergs in the North Atlantic, where the iceberg season lasts roughly from February to October. Greenland and other North Atlantic icebergs are usually peaked and irregular in shape. Antarctic icebergs are tabular, with flat tops and steep sides.
Before the development of radar, sonar and the Global Positioning System, sailors on watch in the Arctic region would listen for distinctive sounds to help them determine whether icebergs were close or far away.
A fantastic variety of shapes result from the deterioration process of icebergs. Despite the fact that no two icebergs are the same, there are certain categories of shapes that are used for iceberg observation. Often the terms, tabular, blocky, wedge, dome, pinnacle and drydock are used.
For those who wish to look beyond the beauty of icebergs, there are many things to look for which can make iceberg watching more interesting. Besides estimating the iceberg's size and shape, there are many features which may be noted. Colored streaks, caves and tunnels, old and new waterline notches and even objects such as boulders or birds are seen on icebergs. Even more spectacular is the occasion of an iceberg calving and rolling which can often be heard from a good distance.
To answer a Press subscriber's question, we did see a lot of small "growler-type" icebergs in the waters near the glaciers in southeastern Alaska on our recent voyage in late July.
These "growlers" can damage boats, because they are nearly impossible to see, especially at night. Most of these icebergs are at least 80 percent under water!
The most famous glacier was the one that sank the Titanic on the night of April 14, 1912. During that time, there was no moon to light up the water as it had already set for the date. The waters were also unusually calm. The iceberg was believed to be much bigger underwater than it appeared above the surface of the ocean. The large object literally cut through the ship like a hot knife through butter.
Also, icebergs were seen much farther to the south than usual at that time of year. A pair of Texas State University astronomers theorized that a rare lunar event, a "supermoon," which is a full or new moon making its closest approach to Earth. These supermoons appear much bigger and brighter than an ordinary moon. This phenomenon also exerts a greater gravitational pull that can magnify the moon's effect on ocean tides. We had a recent "supermoon" this past July.
On Jan. 4, 1912, the most extreme supermoon in 1,400 years may have led to extreme tidal activity that dislodged icebergs from a glacier in Greenland and pushed them southward into the ocean currents and ultimately towards Titanic's path from New York to London on its maiden voyage.
NORTH IDAHO WEATHER REVIEW AND LONG-RANGE OUTLOOKS
The first three weeks of August were the driest on record in the Coeur d'Alene area and most other parts of the so-called Inland Empire. The huge wildfires continued to rage in virtually all directions.
Since early June, we've only received less than a third of our normal precipitation in town. Our skies have been clogged with smoke and dust on-and-off for more than a full month.
This past Wednesday was the 36th day this blistering summer of 2015 with afternoon highs at or above 90 degrees. As of this Friday, Aug. 21 writing, we've likewise observed a half dozen days locally with triple-digit readings.
Nearly 400,000 acres in neighboring Washington were still burning as winds were picking up across the region late Thursday and early Friday.
I wish to thank more than 50 individuals, mostly Coeur d'Alene Press subscribers, that called me this week, not all on Thursday, to ask about the chances of rain in our part of the country between now and early September. I told them that only dust and more smoke was in the 6-to-10-day outlooks for the region, but that God could easily produce rain and change the dire forecasts.
This is what I told more than 100 churches that I called on Thursday across North Idaho. They agreed to pray for rain in their Saturday and Sunday services. The response to my phone calls was overwhelmingly positive. Thanks to one and all.
Our long-range outlooks are quite hopeful for rain as we head towards the very end of August into early September. Keep praying folks that we don't see any more major wildfires in the meantime.
Cliff Harris is a climatologist who writes a weekly column for The Press. His opinions are his own. Email sfharris@roadrunner.com