The Polar Regions

Although the polar ice caps have been in existence for millions of years, scientists disagree over exactly how long they have survived in their present form. It is generally agreed that the polar cap north of the Arctic Circle, which covers the Arctic Ocean, has undergone contraction and expansion through some 26 different glaciations in just the past few million years.

       

  

http://www.youtube.com/watch?v=t7T7beACtQs


North Polar Ice Cap

South Polar Ice Cap


Icebergs

An Iceberg is a floating mass of freshwater ice that has broken from the seaward end of a glacier or a polar ice sheet. Icebergs are typically found in open seas, especially around Greenland and Antarctica. 



They form mostly during the spring and summer, when warmer weather increases the rate of calving (separation) of icebergs at the boundaries of the Greenland and Antarctic ice sheets and smaller outlying glaciers. In the Northern Hemisphere, for example, about 10,000 icebergs are produced each year from the West Greenland glaciers, and an average of 375 flow south of Newfoundland into the North Atlantic shipping lanes, where they are a hazard to navigation. 

  

Cool iceberg video!
http://www.youtube.com/watch?v=pnyK624FC4Y

Polor Ice Fluctuations

The poles go through cycles of ice advance and retreat every year depending on the season. However, it is the average diminishing ice concentrations that trouble scientists. Presented here are two years of ice concentration data from the NASA QuikSCAT satellite. NOAA uses this data to observe major trends in ice concetration.

http://www.youtube.com/watch?v=ZkunS0WmYJk

Light

As light passes through water, it is absorbed and scattered by water molecules, ions, and suspended particles, including silt and micro-organisms.  It is also absorbed by organisms for photosynthesis, to be used in their life process.  This decrease in the intensity of light over distance is known as attenuation.  Seawater transmits only a small portion of the electromagnetic spectrum, primarily in the visible range.  Light energy is attenuated very rapidly with depth, particularly the longer infrared wavelengths.  The intensity of light at any depth can be calculated using Beer's Law: I_z = I₀e ^–kz therefore by rearranging terms  z = -ln(I_z/I₀)/k

The attenuation coefficient k varies with the clarity of the water.  The clearer the water, the smaller the attenuation coefficient and the greater the light penetration.  In typical open ocean water, about 50% of the entering light energy is attenuated in the first 10 m (33 ft), and almost all the of the light is attenuated 100 m (330 ft) beneath the surface.

This graph shows how much visible light (%) broken down into the familiar spectrum of red, orange, yellow, green, blue, and violet and to what depth it can reach.