"Could part of the sea level change be due to warming of the oceans causing expansion of the water?"
I have not seen calculations on that. In general, a one degree rise in water temperature will cause water the volume to expand by about 1/10,000.. i.e. 10,000 gallons of water at 70 degrees Fahrenheit would make 10,000 gallons at 71 degrees. One issue would be that the water is probably not warming all the way to bottom. That's a worthy question though. I'll ask somebody who will know.
How Stuff Works indicates there are 326,000,000,000,000,000,000 gallons of water on earth. If one assumes that the majority is in the oceans, and if the oceans temperature increased by 1 degree, then an additional 32,600,000,000,000,000 gallons by volume would be added. It is estimated 1.6% of all earths water is in the polar ice caps or 5,216,000,000,000,000,000 gallons. Seems like a 1 degree rise in water temperature would raise the oceans a considerable amount.