4-Icebergs and Sea Ice*

Iceberg in New Bonaventure Bay
which is off Trinity Bay (see maps below)

Newfoundland, Canada

Source:www.townofbonavista. com 

Since we just saw our third iceberg drifting by ‘our’ Bonaventure Bay, I thought I will devote today’s blog to the phenomenon of icebergs in general in hopes that there will be a good explanation of how icebergs get into these bays. I must admit, it is time that I give icebergs some thought other than admiring them when I am lucky enough to see them crossing Greenland in a plane.

Source: Environment Canada

Icebergs form when ice calves off glaciers into the sea. Roughly 10% of the mass is above the sea, the remaining 90% are submerged. Incidentally, the latest research shows that the calving of large/huge icebergs actually causes' glacial earthquakes', a function of the calving glacier moving backwards once relieved of its front (the calved portion), then moving forward again. Earthquakes with a magnitude of 5 on the Richter scale have been observed in Greenland. Source: LiveScience.

Since glaciers owe their existence to snow (and pressure), the ice in molten form will be fresh water. Newfoundland’s icebergs calve off the western side of Greenland and then they will remain in cold water ocean currents (blue arrows on map below).

Source: Path of Cold and Warm Atlantic Currents

Icebergs will drift with the current around Buffin Bay in the north and then head southward toward the Labrador Current. The time for an iceberg to reach Newfoundland depends on the location of where it calved, on the wind intensity and environmental conditions an iceberg is exposed to as well as on the currents' speed as they differ somewhat. Overall, it may take between 1-3 years for an iceberg to reach 45 degrees North. Only an estimated 1 - 2% of large (!) icebergs will reach 45 degrees N--this is where they would cross one of the most important routes for ships of the entire Atlantic Ocean and this is where they would encounter the warm Gulf Stream, the North Atlantic Drift (see map above, red arrow).  And, this is where the Titanic encountered its fate in April 1912.

Source: University Corporation for Atmospheric Research (UCAR) 

After the tragic accident of the Titanic, an International Ice Patrol was formed which helped avert another such tragic iceberg-ship collision; however, collisions do occur.

Below you see a map produced by the International Ice Patrol for July 2, 2014. As one can see the outer iceberg limit is beyond 45 degrees N, so these icebergs will definitely have an impact on shipping. Below see the warning that was posted for all ships in the area:

Source: weather.noaa.gov.

As mentioned above, ship collisions with icebergs occur relatively frequently. Here is a chart showing
particulars on this topic:

Source: National Geographic

Iceberg frequencies appear to have increased as would be logical considering that global warming would cause more ice to break off continental glaciers. The following graph shows iceberg occurrence for 108 years and it appears that frequencies increase, even when discounting extreme years such as 1984 and 2007.

The chart below shows the locations of known ship-iceberg collisions within the time frame of 110 years, from 1890 to 2000:

Chart showing known locations of ship collision with icebergs in the NW Atlantic
 Credit: Brian T. Hill / Institute for Ocean Technology 

 Sea Ice

In contrast to icebergs -- the product of ice formed over continents--sea ice is simply frozen ocean water; it grows and melts in accordance with the prevalent temperatures. Roughly, 15% of the world's oceans are covered by sea ice during part of the year.

Instead of absorbing the energy, ice surfaces reflect solar energy back into the atmosphere which keeps the temperatures in polar regions relatively cool. It thus follows that the more sea ice melts the more energy water will be able to absorb and thus the warmer the globe will get. The warmer it gets the more sea ice will melt--so this is a cycle that reinforces itself temporarily stopped by the polar nights.

Sea ice is instrumental for the formation of ocean currents. As sea ice forms, salt is for the most part pushed into the water below the ice. Water with high salt content has a greater density than salt-free water and sinks. Cold, dense and salty water sinks and moves towards the equator along the bottom of the oceans with warm water  flowing from the equator on top of it. It therefore follows that  if there is less sea ice, a change in the ocean currents will occur at some point.

The extent of sea ice is closely monitored; below you find a graph showcasing the last four years which is contrasted with the mean value of the last 20 years of the 20th century.

Copyright (2014) EUMETSAT 

Because sea ice is under the effect of winds, currents and temperatures, it undergoes various deformations. Thus it is usually classified according to age and according to its drifting ability. If the ice is attached to land or an iceberg, it is considered fast ice (= fastened ice), otherwise  it is called drift ice.The boundary between fast and drift ice is called fast ice boundary. Drift ice itself  can be found more offshore and is broken up into large pieces, the floes. Pack ice refers to either drift ice proper or to an area which has a lot of floes closely packed together.

Arctic Sea Ice Extent March 2014
Credit: National Snow and Ice Center

* NOTE: The source for the content of this blog originates from public domain sources such as Environment Canada, the University Corporation for Atmospheric Research (UCAR), the National Snow and Ice Data Center, Ocean and Sea Ice SAF, National Geographic, and EUMETSAT.