merijääpeitteissä

Merijääpeitteissä refers to the frozen seawater that covers parts of the Earth's oceans. This phenomenon is most prevalent in the polar regions, particularly the Arctic and Antarctic oceans. The formation of sea ice begins when the ocean surface temperature drops below the freezing point of saltwater. Unlike freshwater ice, sea ice typically forms at around -1.8 degrees Celsius (28.8 degrees Fahrenheit) due to the presence of salt.

As the water freezes, most of the salt is expelled, a process called 'brining'. This leaves the ice with a much lower salt content than the surrounding seawater, although it is not entirely fresh. Over time, this trapped brine can migrate out of the ice, making older sea ice less salty.

The extent and thickness of sea ice cover vary significantly throughout the year due to seasonal changes in temperature. In the summer months, sea ice melts and retreats, while in the winter, it expands and grows. This seasonal cycle is a critical component of the Earth's climate system, influencing ocean circulation, weather patterns, and albedo (the reflectivity of the Earth's surface).

Sea ice plays a vital role in polar ecosystems, providing habitat for various species, including seals, polar bears, and penguins. It also affects human activities in polar regions, such as shipping, fishing, and resource exploration. Scientific research on sea ice is crucial for understanding climate change, as the observed decline in Arctic sea ice extent over recent decades is a significant indicator of global warming.