 Solution

Long-term thinning lowers the latent heat inventory that must be supplied before a patch of sea ice disappears. Thin ice is also more mobile and vulnerable to mechanical breakup. A smaller fraction of multi-year sea ice therefore increases susceptibility to a warm or windy summer. Thin ice grows relatively rapidly in winter because it conducts heat more readily, giving a stabilizing response that partly opposes continued thinning without cancelling sustained warming.