greasjäästä

Grease ice is a term used in glaciology and oceanography to describe a very early stage of sea ice formation. It appears as a soupy, oily layer on the surface of the water, resembling grease or slush. This stage is characterized by a concentration of ice crystals that are not yet interlocked or frozen together to form a solid sheet. The crystals are typically small and dispersed, giving the water a duller appearance than the surrounding unfrozen ocean.

Grease ice forms when the water temperature drops below its freezing point, which is slightly lower than that of freshwater due to the presence of salt. As the water cools sufficiently, ice crystals begin to nucleate and grow. These initial crystals are often disc-shaped and float independently. They gradually accumulate, forming the characteristic greasy texture. This stage is transient and can develop into other forms of sea ice, such as frazil ice or nilas, depending on factors like wind, wave action, and further cooling.

The formation of grease ice is an indicator of impending significant sea ice development. It is often observed in polar regions during the onset of winter. Understanding grease ice is important for predicting the progression of sea ice cover, which has implications for navigation, climate studies, and marine ecosystems. The transition from grease ice to more consolidated ice forms can occur rapidly if conditions remain favorable for ice growth.