Major changes have occurred in the Arctic Ocean over the last two decades, including the unprecedented spin-up of the Beaufort Gyre circulation and the emergence of Arctic Atlantification. The Arctic atmospheric circulation over the Canada Basin was unusual. However, the wind-driven spin-up of the Beaufort Gyre would have been much weaker had it not been for sea ice decline. The sea ice decline not only fed the ocean with meltwater, but also made other freshwater components more available to the Beaufort Gyre through mediating the ocean surface stress. This dynamical effect of shifting surface freshwater from the Eurasian Basin towards the Amerasian Basin also resulted in halocline salinification and the uplift of the halocline lower boundary in the eastern Eurasian Basin. Numerical simulations reveal that, in comparison to the sea ice condition in the 1980s, the sea ice condition in the 2010s increases the response of the Arctic Ocean to Arctic Oscillation and Beaufort High wind perturbations by up to 50% for integrated freshwater content and by up to about 100% for upper ocean velocity regionally. The Empirical Orthogonal Function (EOF) analysis of Arctic annual sea surface height for the last two decades indicates that the first two modes of the upper ocean circulation have active centers associated with the Arctic Oscillation and Beaufort High variability, respectively. In the presence of sea ice decline, the first two EOFs can better distinguish the ocean variability driven by the two atmospheric circulation modes. Therefore, the recent major changes in the Arctic Ocean are indicators of climate change as is the sea ice retreat. Analysis of CMIP6 models reveals that the Arctic Ocean is one of the ocean areas most susceptible to climate change. We identified that the Arctic Ocean warms faster than the global average, a phenomenon we call Arctic Ocean Amplification.