Today only three populations of gray whales are found in the Pacific Ocean. The North Atlantic population was extirpated in the early 18th century.
Nevertheless, in 2010, two observations were recorded in the Mediterranean: one off the coast of Israel and another off of Barcelona, Spain. Researchers were able to confirm that it was the same individual. In 2013, a new sighting was recorded off the shores of Namibia, in Africa.
Based on DNA analysis of gray whale fossils, the Atlantic and Pacific populations used to be the same population. The results, published in 2015, reveal that dispersion between the two oceans took place several times before and at least once after the last ice age.
Today, melting Arctic sea ice is opening up the Bering Strait and the Northwest Passage to the Atlantic Ocean. Thus, whales could more easily stray north and stay longer in the area to feed. The absence of ice might allow them to travel from west to east.
These genetic data on gray whales and recent observations in the Atlantic suggest the possibility that this species might be expanding its range again.