Ice mélange refers to a mixture of sea ice types, icebergs, and snow without a clearly defined floe that forms from shearing and fracture at the ice front. Ice mélange is commonly the result of an ice calving event where ice breaks off the edge of a glacier. Ice mélange affects many of the Earth's processes including glacier calving, ocean wave generation and frequency, generation of seismic waves, atmosphere and ocean interactions, and tidewater glacier systems. Ice mélange is possibly the largest granular material on Earth, and is quasi-2-dimensional.
Etymology
Mélange or melange means "mixture" and originates from the Old French word "meslance". Ice mélange has also been referred to as "sikkussaq" or "sikkusak", which is a Greenlandic word meaning packed by ice or surrounded by sea ice. The word is derived from the word "siku", which means sea ice.
Influence on fjord seiches
Fjord seiches are created by the calving and capsize of large icebergs and mélange movement. It has been shown that such events create long-period, large-scale surface gravity waves and seiches. The presence of ice mélange slows down the propagation of both external and internal seiches and introduces band gaps where energy propagation (group velocity) vanishes. If energy is introduced into the fjord within the period range covered by a band gap, it will remain trapped as a fading oscillatory mode near its source, thus contributing to localized energy dissipation and ice mélange fragmentation. Understanding the connection between seiches and ice mélange is important for several reasons. First, seiches cause commotion within the mass of ice mélange that typically fills the fjord, thereby causing further break-up and capsize of the sea ice. Second, their relationship determines how the fjord will respond to forcing by the external ocean beyond. Third, seiches offer a means of quantifying the energy associated with iceberg calving and capsize, when direct local measurements of the event are impractical due to the hazards of deploying instruments on or below ice mélange.
Examples
Jakobshavn Isbræ, Greenland
The Jakobshavn Isbræ, or Jakobshavn Glacier, has a large drainage basin and is one of Greenland’s largest and fastest-flowing outlet glaciers. Large calving produces a long floating ice tongue that rapidly melts in spring suggesting that the tongue is formed by a dense pack of calved icebergs and is an ice mélange. Through visual observations of Jakobshavn Isbræ’s proglacial ice mélange it can be determined that the mélange forms a semirigid, viscoelastic cap over the innermost 15–20 km of the fjord, motion of the mélange is primarily contained by deformation within and along the margins of the mélange, and icebergs within the mélange gradually disperse and become isolated from each other as they move down the fjord. Seasonal variations in ice mélange strength can influence the evolution of Jakobshavn Isbræ’s terminus position, and therefore glacier flow. Sea ice formation in winter solidifies the ice mélange and bonds icebergs and large ice masses, thereby increasing the mélange buttressing of the glacier terminus. Thus, sea ice and ice mélange act together to influence glacier breakup dynamics by preventing calving and enabling the terminus to advance. In addition to the rapid horizontal movement of the ice mélange during calving events, ocean waves generated by calving icebergs cause the mélange to experience vertical displacements.