Sea ice thickness measurement using episodic infragravity waves from distant storms

© G.Redvers/Tara Expeditions

Tara Arctic

Peter WADHAMS, Martin J. DOBLE

Cold Region Science and Technology, Volume 56, Issue 2-3, May 2009, p.98-101.

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The thinning and retreat of Arctic sea ice is one of the most dramatic manifestations of recent climatewarming. Though ice extent can be routinely monitored by satellite, ice thickness is far more difficult tomeasure operationally.We show that small amplitude, long period waves — termed infragravity waves — canbe used to measure ice thickness at basin scales by determining their travel time between measurementsites. The waves travel at a different speed in ice than in open water, the difference being a sensitive functionof ice thickness. We present measurements from near the North Pole where the travel time of 15 s waves isreduced by around 7 h for a typical 2 m ice thickness. Our results demonstrate that a basin-scale observationnetwork which can track the effect of global change on Arctic sea ice thickness is practical and feasible usingcurrent technology.