Harrold Bergman moved into Arthur harbor in the beginning of March, the year 2010 (see photo: Harrold at the mouth of Arthur harbor). Since then he has been twisting and turning, turtling and calving, and showing us many new faces. He has been included in many of our photos for the UAB team in Antarctica, but seems to be shrinking day by day. I tried to take photos of him every day this past week to see if we’d notice a change in composure, composition, but perhaps the myriad of photos donated to this blog may show changes better.
Ice bergs have a distributed mass above and below water; 10% above and 90% below. Because of this they run aground on the varied bathymetry of the harbors and inlets around Antarctica, scouring all the animals and plants off the bottom. Harrold is presumably atop a small ridge which is a rim in the bowl shaped Arthur Harbor. The berg turns the water around it an aquamarine color deceiving your senses into the expectation of rustling palms and sweet pina coladas (see photo harrold2). This color is present in the berg after a rain (see photo 3.27 close up) and turns it a blue shade which is accentuated by any snow fall. The sun and clouds often change the color of the mountains, glaciers and icebergs into an array of Easter-like hues on clear days around here, which are becoming few and far between. And still it is cold.
Ice bergs are created by calving of a glacier, which is the weakening of the glacial ice by tidal fluctuations resulting in a separation of glacier and ice. There are many classes of iceberg. Harrold seems to be a medium sized iceberg meaning he is around 15-45 meters tall and 60-120 meters wide. Other sizes are classified as small, large and very large (very scientific).
The smaller bergs are called either “growlers” if they are less than 1 meter by 5 meters or are called “bergy bits” if they are from 1-5 meters by 5-15 meters (see photo hero to harrold). To describe the shape of the iceberg you first categorize it as either tabular or non-tabular, meaning that it looks like a plateau or it doesn’t. If it is non-tabular then the berg can fall into the categories of a dome, pinnacle, wedge, dry dock, or blocky (which is the same as tabular but in the shape of a block). The iceberg sheds layers by calving itself, creating the growlers or bergy bits and brash ice we often see in Arthur Harbor (see ice water and brash photos).
Harrold had a friend named Monty (see photo harrold and monty), who was a large dry dock, and he came to visit for three days. We could see him for two days past Norsel Point, and then he moved on east pausing at Killer Whale rocks to greet Harrold for a day (see boating map for a better track image). Now he is off somewhere to the South East I believe.
Ice bergs are generally driven by strong subsurface currents, because most of their mass is below water. Wind driven currents and strong winds that we see in Antarctica don’t have nearly as strong an impact on these large ice chunks as you may think. It’s important to watch the track of an iceberg, especially in the North Atlantic, where they can enter shipping channels, and most famously sink boats (such as the Titanic). Icebergs are monitored for shipping and oceanographic purposes in the Antarctic by the National Ice Center (http://www.natice.noaa.gov) and to track global change caused by shifts in iceberg production or loss of ice shelves (http://www.hamilton.edu/news/exp/larissa).
Harrolds bit-by-bit death, perhaps untimely because of his prolonged and sedentary stay in Arthur harbor, brings a slough of brash ice and a film of ice cubes on the surface of the water when the winds are right. This of course is not the only source of the ice, the glacier also calves regularly as Jim discussed in detail earlier this season. Icebergs can take anywhere from a day to four years to melt depending on the temperature above and below water, the sun, their movement and size. People prognosticate that Harrold will melt away, or ‘explode’ before the end of April. It will be a sad day when our friend who has been here as long as we have, takes leave of us and scatters across the sea.
This blog was brought to you by Kate Schoenrock. Photos were generously provided by Stacey Murray and John Alan Maschek, and many more than are linked here are in our Flickr photostream. Much of the information from icebergs is from solcomhouse.com. You can go to this link to learn more about Antarctic icebergs: http://www.solcomhouse.com/Antarctica.htm