Why recent water temperatures in the North Atlantic have scientists buzzing

It's been well documented that ocean temperatures have been on the rise across the globe for the past few decades.

However what's happening with the warming waters in the North Atlantic over the past few weeks has the science community buzzing. 

Temperatures in the North Atlantic are warming at new record levels this spring, based on data compiled by NOAA satellites and produced by the University of Maine.

In early June, sea surface temperatures in the North Atlantic were as warm as 0.5 degrees above the previous record and more than one degree above the 1982-2011 average. 

The reason for this recent record warmth of 2023 is still under investigation.

Climate scientists agree that climate change and the ongoing warming in our oceans is no doubt a contributing factor. However they also agree that it is much more probable there are multiple factors at play right now. 

Blocking pattern in the North Atlantic

One of the most likely factors is the recent atmospheric setup over the North Atlantic. Over the past few weeks and months, you've no doubt heard me talking during my forecasts about the persistent blocking pattern over the Labrador Sea, Greenland and Iceland.

This pattern has led to the lengthy stretches of cooler and wetter weather we've experienced this spring in Atlantic Canada — particularly last week, when parts of the Maritimes saw over 100 mm of rain in just five days.

This blocking setup in the high latitudes of the North Atlantic means that there is higher than normal pressure in that region. This also typically leads to lower than normal pressure near Bermuda and the Azores, which has been the case this spring.

A weaker sub-tropical high equates to weaker easterly trade winds. These winds increase upwelling of cooler water from below the surface. Without those strong trade winds, there's a greater opportunity for the tropical Atlantic Ocean to bake in late spring sunshine.

As a result, one of the areas with the largest sea surface temperature anomalies right now is in the "Main Development Region" in the tropical Atlantic. This area, which is key for tropical development, is already reaching temperatures not normally seen until August and September. 

Saharan desert dust

Another possible factor is that there is much less dust than normal over the Atlantic Ocean right now.

Weaker easterly trade winds mean less clouds of dust blowing from the Sahara desert and into the North Atlantic.

These clouds of dust generally have a cooling effect this time of year, as they reflect away the solar radiation that heats the ocean water.

A 2021 NASA study predicted less Saharan dust in the coming years, largely in part due to warming ocean temperatures in the North Atlantic.  

Impacts on hurricane season 

No matter the causes, this record warmth in the North Atlantic is not good news for hurricane season.

Warmer tropical Atlantic Ocean waters typically lead to more tropical storms and hurricanes, with more fuel available for developing systems.  

However as discussed in the hurricane outlook a few weeks ago, a rapidly developing El Niño may help counter any storms that do develop in the tropical Atlantic.

El Niño events typically lead to stronger wind shear in the tropical Atlantic. This wind shear can suppress the development and growth of tropical storms. 

The atmospheric battle of the warming Atlantic vs. the ongoing El Niño will be one to watch throughout the summer and fall.