Fields of Green

A continent of purest blue begins to flow, an unstoppable force

That spills towards the sea in cinematic slow motion.

Pristine shades of sapphires that break apart

Across the grounding line; a shattered

Kaleidoscope of powder and

Periwinkle that bares the

Effervescence of its

Contents.

 

Torn free from their shackles these shattered monuments drift menacingly across a desolate Seascape, broken colossi of ice that enticingly allow only the tiniest sliver of frozen flesh to

Break the surface.

 

Hidden amongst          this      frigid   minefield –

a          jaded emerald

made   from    the       grounded minerals     of

a distant          home. Conspicuously  it picks its

way     through           the       glaring crowds, and

floats   purposefully towards more open      waters.

 

Embraced by every warmer wave,

The stone is hewn in two;

And softly falls in to its grave,

So life may start anew.

A green iceberg sighted in the Weddell Sea, Antarctica on February 16th, 1985 (Image Credit: AGU/Journal of Geophysical Research: Oceans/Kipfstuhl et al 1992).

This poem is inspired by recent research, which has found a possible explanation for why some icebergs are green.

The Antarctic Ice Sheet is a giant mass of glacial ice that flows outward from the mainland of Antarctica to float on the ocean as an ice shelf, and at the front of this ice shelf tides and currents cause large chunks of ice to break off and float away as icebergs. The ice from glaciers tends to blue because in ice the absorption of light at the red end of the spectrum is six times greater than at the blue end, which means that almost all of the light apart from blue light gets absorbed before it reaches our eyes. Any bubbles in the ice cause it to appear less blue, as they scatter the light before it can be absorbed.  As icebergs tend to be made up of ice that contains some bubbles, they normally appear bluish-white in colour. However, explorers and sailors have long reported seeing green icebergs around certain parts of Antarctica, with scientists previously unsure as to what causes this colouration.

This new research proposes that iron oxides in rock dust from Antarctica’s mainland are responsible for the green hue of these icebergs. As glaciers flow across rocks on the mainland, they grind them into a fine powder known as glacial flour. When these glaciers encounter the sea, this glacial flour flows into the water, but if the rock dust becomes trapped under the ice, then these particles can instead become lodged inside an iceberg when it breaks away. Measurements of ice from the Amery Ice Shelf (a large body of floating ice in East Antarctica) have revealed high concentrations of iron, suggesting that it is indeed iron‐oxide minerals that are causing some icebergs to turn green. As iron is a key nutrient for phytoplankton (the foundation of the oceanic food web), this would suggest that green icebergs might play an important role in helping to support marine life, by transporting iron from the Antarctic mainland to the open ocean.

An audio version of this poem can be heard here:

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