The North Atlantic is experiencing record-breaking warmth, with sea-surface temperatures soaring to almost 4 degrees Celsius above normal. The anomalous warming is occurring in a large swath stretching almost one-third of the way across the Atlantic westward from the northwestern coast of Africa. Scientists are concerned that the warmer-than-normal waters might help strengthen storms that form in the eastern Atlantic and eventually spawn hurricanes.
Unprecedented Warming in the North Atlantic
Satellite data reveal that some surface waters in the area are almost 4 degrees Celsius (about 7 degrees Fahrenheit) above normal for this time of the year. The average sea-surface temperature for the portion of the Atlantic that stretches from the equator to 60 degrees north was 22.7° C (nearly 73° F) on June 10, about 1 degree C higher than the average recorded from 1991 through 2020. The previous record for the same date occurred in 2010.
Possible Factors Contributing to the Warm-Up
The cause of the unusual warm-up isn’t clear, but here’s a rundown of several factors that might be at play.
The dearth of Sahara Dust:
Occasionally, vast swathes of desert dust from the Sahara waft across the ocean, carried by winds stirred up by a semi-permanent high-pressure system dubbed the “Azores high” due to its proximity to those islands. But lately, the Azores high has weakened and shifted southwest away from Africa. So those winds that typically pick up and transport Saharan dust westward over the North Atlantic are calmer and largely dust-free. As a result, solar radiation that normally would be scattered back into space by the dust reaches the ocean surface, warming the dark waters.
Decreased Air Pollution:
In 2020, new emissions rules kicked in for long-haul container ships that spew sulfate-rich exhaust plumes. There’s been some speculation that less pollution could lead to more heating. With fewer plumes scattering sunlight back into space, more radiation reaches the sea surface. But some studies suggest that the cooling effect of ship plumes may have been minor to begin with.
Global Warming Trends:
This year marks the return of El Niño, a climate phenomenon whose hallmark is warmer-than-normal sea-surface temperatures along the equator west of South America. In general, El Niño boosts average surface temperatures both on land and at sea worldwide. Human-caused climate change has done the same.
Uncertainty Surrounding Hurricane Formation:
The unusually warm waters of the North Atlantic may tend to strengthen storm systems that later develop into tropical depressions and then hurricanes. But the El Niño that’s now developing in the equatorial Pacific may hamper their formation by strengthening winds in the upper atmosphere that can shear the tops off nascent hurricanes. How active this year’s hurricane season will be depends on which of these forces will prevail.
In conclusion, the unprecedented warming of the North Atlantic is a cause for concern, especially given the potential impact on hurricane formation. While the exact cause of the warm-up remains unclear, a combination of factors related to climate change and natural variability could be at play. As always, scientists will continue to monitor the situation and provide updates as new information becomes available.