Last Thursday, blue whales were spotted in Southern California's Del Mar and La Jolla. Experts report that this is the closest these large mammals have ever come to our shores.

Some say this could be explained by the recent upwelling of cold ocean water this summer. Upwelling is a phenomenon that refers to wind-driven water, usually cooler and richer in nutrients, replacing the existing warmer water in our ocean. More people using the beaches in hot weather results in upwelling.

Because of the increase in upwelling regions, there has been an increase in krill around this region as well. These crustaceans are regular prey of blue whales, so this may explain why they have been swimming closer to shores this summer.

Compared to gray whales, blue whales are said to have a less regular migratory pattern. Now, this unpredicted pattern could continue bringing blue whales closer to our shore. As upwelling persists, they could be staying nearby until the end of the month. If so, this is a good whale watching season to catch sightings of the world's largest mammal.