"Winter ice" refers to the frozen water that forms during the coldest season of the year, winter. It is the solid state of water when the temperature falls below freezing, turning it into ice. Full definition
Is it thicker snow cover with subsequent slowing down of winter ice thickness growth rate? (neven1.typepad.com)
An area of ocean that extends from the permanent ice zone to the boundary where winter ice extent is at a maximum. (searcharcticscience.org)
As a result, more and more winter ice is growing on open stretches of water, making it thinner and more vulnerable to melting during its first summer. (newscientist.com)