California has been in the news lately for the impacts of its ongoing drought on agriculture, forests, and municipal water. Far less attention has been paid to what is going on in the Pacific Ocean just off its coast. That’s a shame, because this region is in the throes of a sea surface temperature anomaly that has been dubbed the “warm blob,” which is wreaking havoc on sea lions and sea birds, and may even be one of the causes of the drought.
To understand what is going on, it is important to first understand the California Current, which flows from the Gulf of Alaska down along the West Coast. The current can be thought of as the inverse of the Gulf Stream; it is caused by the same types of large-scale forces in the ocean and atmosphere. But where the Gulf Stream sends warm water toward northern Europe, the California Current sends cold water southward. It is the cause of the cool summers and foggy conditions that the northern California and Oregon coasts are known for, and it sets up prevailing winds from the warmer land surface that push waters offshore. This pushes nutrient-rich waters up from the ocean bottom toward the surface – a process called upwelling. This upwelling in turn drives tremendous plankton growth, the basis of the local food chain, and creates a thriving environment for fish, birds and marine mammals.
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At least, that’s how it is supposed to work. But since the fall of 2013, the cold waters in the Gulf of Alaska – the ones that the California Current should be sending down the West Coast – haven’t been very cold. In fact, they’ve been about 5o degrees warmer than normal, over an area 1,000 miles across and 300 feet deep. Climatologists are calling this the “warm blob.” The blob seems to have its origins in warmer temperatures thousands of miles away in the tropics. Now it is big enough that it has impacted weather across the continent. The associated ridge of high-pressure air is powerful enough to warp the jet stream, contributing to California’s drought by keeping warm, dry air over that region, while funneling Arctic air toward the northeastern U.S. A recent study connected the “warm blob” to the very cold winters in the Northeast over the past two years.
It turns out that what is good for sweater sales in New England is terrible for wildlife in the Pacific Ocean. Since the cold water of the current is needed to drive the upwelling of nutrients that feed the whole food chain, the anomalously warm waters of the “blob” have caused a precipitous decline in upwelling. In turn, scientists are seeing very low populations of the tiny, shrimp-like creatures called copepods that are a dietary staple for many of the fish off the California coast. And the effects of these changes on marine life are becoming tragically evident, particularly for sea lions and seabirds.
In January 2015, sick and starving sea lion pups began stranding in alarming numbers on California’s beaches. These pups, born the summer before, should still have been with their mothers, nursing and fattening up to a weight of 70 pounds or more. Instead, many were closer to the weight of a newborn (20 pounds). Many were also dehydrated, and suffering from ulcers and respiratory infections as well, which indicates stress and malnourishment. Normally, fish are abundant near the sea lions’ breeding grounds. But it appears that the absence of nutrient upwelling has driven the fish out to deeper, colder water further offshore. Female sea lions, in turn, must abandon their pups for long periods of time and venture much further afield to forage. Between the longer time left alone, and the extra energy that the mothers expend to travel, the pups are simply not able to get enough to eat. As of mid-April, the number of pups that had stranded on California beaches had skyrocketed to over 2,500. Nearly half of these have died, despite heroic efforts from rehabilitation centers.
And sea lions aren’t the only species suffering. Cassin’s auklets are robin-sized seabirds that gather in flocks up and down the West Coast to feed on copepods and other plankton in the upwelling zone. Over the past year, they have been dying in “massive, unprecedented” numbers – thousands have washed ashore, and the total number of dead has been estimated at 50,000 to 100,000. Tellingly, they don’t appear to have died from illness or exposure to toxins; instead, it appears they have starved to death. As with sea lions, food web changes associated with the “warm blob” – namely a dramatic reduction in plankton numbers – seem to be the major culprit.
The big question that no one has definitively answered yet is: Is the warm blob the product of climate change? Perhaps not. It may actually be mostly driven by long-term ocean cycles, and may signal that the start of an El Niño cycle or a shift in the longer-term Pacific Decadal Oscillation, (PDO), which has been in a cool phase for the past five years or so, and may be moving into a warm phase. Both El Niño and warm-phase PDO take heat stored in the ocean and transfer it to the atmosphere. The bad news is that the ocean has been storing an awful lot of heat, since 90% of the extra heat from climate change ends up being stored in the ocean. So either shift may bring a spike in global air temperatures in the year ahead. Either way, what’s taking place in the Pacific Ocean now is almost certainly a glimpse of what a warmer future will look like.
Author
Aimee Delach
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