There has to be liquid water in the Arctic Ocean to produce the snow that cools earth by increasing ice volume, advancing ice extent and increasing albedo. Every time earth gets warm, at some point, there is liquid surface water in the Arctic and then it snows and earth cools after every warm time. When earth is cool, there is no liquid surface water in the Arctic and it doesn't snow much, land ice melts and retreats and earth warms after every cool time.
Before the current ten thousand years, 130k years ago, 240k years ago, etc., water did not enter the Arctic until much of Greenland Ice melted. Therefore, it had to get warm more than now and the oceans wound up fuller than now, using the melted Greenland Ice, and the fuller oceans produced more snow than now to cut off the warm flow into the Arctic. That is why we had major warming and major ice ages then and not now.
Now, water always flows through the Arctic and a much smaller warming can melt the Arctic Sea Ice and turn on earth's ice machine with little or no help from Greenland Ice. A much smaller cooling can freeze the Arctic surface and it is not necessary to drop the oceans much to turn off the ice machine.
Now, in this ten thousand year warm period, we have warm and cool cycles with tighter limits and we have ocean rise and ocean fall with tighter limits. This will continue.
This is all in the ice core data. No model, other than earth and earth's data, is required to understand this.