evidence: Rising sea temperatures lead to reduction in polar bears since the last ice age [...] We see a disturbing link between population decline and environmental changes. A relatively small increase in the sea surface temperature, and in turn a small reduction sea ice, resulted in a rather dramatic decline in the population of the polar bear. [...] "We see a disturbing link between population decline and environmental changes. A relatively small increase in the sea surface temperature, and in turn a small reduction sea ice, resulted in a rather dramatic decline in the population of the polar bear. The relationship is not linear," continues Eline Lorenzen.