Eustasy video

Eustatic sea-level changes refer to the world-wide changes in the height of the sea surface with respect to land areas.  In regards to long term climate changes, eustatic sea-level change is largely due to changes in the amount of water locked up in the ice sheets and mountain glaciers.  As an ice sheet melts, sea level rises and as ice sheet grows, sea level falls.  This process also happens on shorter timescales, and the research project I am working on at the moment is looking to see how changes in the ice sheets has affected sea level over the last 500 years in the North Atlantic.

A logical idea, however, I thought it would be fun to make a video to show the students this process as it is one of the main causes of sea-level change.  I slightly underestimated how long it would take my freezer to make a mini ice sheet (with blue food coloring – to make it more interesting and make the sea level change clearer), however, once my ice sheet had frozen, I used time lapse photography to create a video of the ice melt causing eustatic sea-level rise in an 'ocean' in my kitchen!

The finished product:

One must be aware that this video suggests the sea level rises uniformly across the whole ocean as the ice sheet melts.  In regards to ice sheets and mountain glaciers, the picture isn’t that simple as a big lump of ice has its own gravitational field, in the same way as the moon does. When the ice sheet is at its biggest, the sea is pulled towards the ice, resulting in higher sea level closest to the ice sheet.  When the ice melts, the ‘ocean tide’ moves away from the ice sheet and the greatest sea level rise is in fact furthest away from the ice sheet.  More details can be found in this research paper.  Our present research project trys to pick out these patterns of sea-level change around the North Atlantic to work out which ice sheets may be contributing to sea-level change.