Cold land, Warm oceanIt's warm but there's lots of snow. According to "Watt's up with that" the land surrounding the Arctic ocean is cold, but the oceans are warm. Warm ocean means lots of precipitation falling as snow in winter. Now it is interesting to look at how the last Interglacial ended. The temperature rose (sea level fell) steadily and faster than during the current Interglacial. Then it crashed with the sea level falling at 1cm a year: That's a lot of snow and ice build up.
Maybe at the end of an Interglacial the ocean is warm, but then the Sun gets weaker, and/or lots of junk gets thrown into the atmosphere by volcanoes. So the land gets cold. Lots of snow. Not enough Summer melt. Bingo.