The International Hydrographic Organization recognizes the Arctic Ocean as an ocean, although some oceanographers call it the Arctic Mediterranean with limited pathways and water exchange with the larger sub-Arctic oceans. There are two main pathways by which the Arctic Ocean connects with the global ocean circulation, notably the Pacific-Arctic Ocean and the Atlantic-Arctic Ocean gateways. Standard processing of satellite radar altimetry is faced with severe difficulties in the presence of sea ice and as such they do not provide regular routine monitoring of the Arctic sea level. The key approach to derive sea ice thickness estimation in the Arctic Ocean is by satellite altimetry. The caveat is that the uncertainty estimation is challenging and that the existence of in situ observations of snow depth, snow density, and sea ice thickness are sparse. The averaged Arctic sea level change also exhibits large interannual variation and the shorter averaging period reveals a period of sea level increase and sea level drop.