All About Ice!

Both the North and South polar ice caps play a huge role in the Earth's hydrologic cycle.  The ice caps have existed for millions of years and their fluctuations in size have direct affects on life on Earth.  At least 5 times during the Earth's history the ice caps have expanded both north and south towards the equator and remained there for around a million years.  These phases are known as ice ages.  In more recent history, the yearly fluctuations of the ice cap sizes determines how much water is locked into the ice caps and therefore how much free water is flowing through the World Ocean (thus affecting the mean sea level). 

Below are pictures of the North and South polar ice caps.

North Pole (changes in extent between 1979 and 2003)

Thermal View of South Pole (Antarctica)

When large pieces of ice are either melted or broken off of the ice caps, icebergs are formed.  Icebergs are giant free-floating packs of ice that are larger below the surface than above (typically only one ninth of the iceberg is shown above water).  A beautiful picture of an iceberg during sunset off the coast of Newfoundland is shown next. 

Iceberg during sunset around Newfoundland

Icebergs can also make fairly interesting noises as they move and pass each other.  Such sounds are documented and examples can be heard in the video provided through the link below.  *Noises get really interesting at 1:26!!!

Noisy Icebergs

Below is a map produced to show the extent of ice present around the North Pole in both the winter (left) and summer (right).  This image was created using the SSM/I (Special Sensor Microwave/Image) on the DMSP series of Department of Defense satellites.  The black dot on the images represents the North Pole.  As you can see, the ice extends much further south into the Atlantic, throughout North America and Europe, during the winter than it does during the summer. 



Light Attenuation for Various Colors of Light in Water

A light's wavelength is directly related to how deep the light can penetrate a body of water.  As light travels through water, it is scattered and absorbed by the water molecules, ions and particulates in the water.  The decrease in light intensity over distance is referred to as attenuation. 

Beer's Law can be used to determine how much of a light source reaches what depth of water based on its wavelength and corresponding attenuation coefficient.  Based on the attenuation coefficients for red, orange*, yellow, green, blue and voilet light, their calculated % Incident Light versus Depth of Water are shown below in Figure 1.  All colors start at a % Incident Light of 1% because the natural log cannot be taken for 0%. 

Figure 2 shows the same information but on a logarithmic scale to yield straight lines. 

*Note: Two coefficients were given for the color range of orange so the graphs show lines for an Orange1 with a coefficient of 0.650m^-1 and an Orange2 with a coefficient of 0.350m^-1. 

 Figure 1

Figure 2

As the figures suggest, as a light's wavelength increases (red has the largest wavelength, violet has the smallest) the light is attenuated more quickly.  Hence, colors like red and orange attenuate much faster than blues and violet.