It's just not that the oceans are warming over time. The largest body of water on Earth is the Pacific Ocean and its warmth is overwhelming the North American climate system. While you have blocking like a -EPO, -AO, -NAO you would think it would be very cold and forcing cold out of Canada, but reality is that we instead get the relative warmth off the Pacific Ocean not allowing the normal cooling effects from land and radiational cooling. Like you said though Arctic ice melt is also probably at play as well and that is melting because the lower latitudes are on fire along with the oceans too.