In the midst of debates about climate change and its effects on the oceans, a puzzle has captured the attention of scientists and experts, as it defies the trend of warming of the oceans. This mystery is an anomaly in the current landscape and is located on the Atlantic coast of Canada and Greenland.
Called the "cold blob," this phenomenon has been under observation for the past decade in the area. This term is used to refer to this unusual and mysterious nature, as it represents a patch of cooler temperatures amid global warming of the oceans.
Experts point out that this phenomenon is related to the slowdown of a global ocean circulation system known as the Atlantic Meridional Overturning Circulation (AMOC). This is responsible for transporting warm water from the tropics to the north of the Atlantic and sends cold water to the south, below the surface.
A new study suggests that large-scale weather patterns may also influence the formation of the "cold blob." This analysis highlights the importance of the North Atlantic Oscillation (NAO) in the formation of the phenomenon. And it is that during the positive phase of the NAO, the winds over the subpolar North Atlantic intensify, promoting a loss of heat similar to removing the surface of a hot liquid to cool it.
Laifang Li, a professor at Pennsylvania State University and co-author of the research, explained that this process is similar to cooling a hot cup of coffee, where intensifying winds at the ocean surface have a similar cooling effect.
“When we want to cool a hot cup of coffee, we stir the surface, and that promotes heat loss. That is exactly what intensifying winds are going to do with the ocean surface – it has a direct cooling effect,” she detailed.
The researchers suggest that the NAO may play an equally important role as the AMOC in creating the "cold blob." The positive phase of the NAO has become more dominant in the last century, which helps explain the persistence of this anomaly.
"Previous studies have focused primarily on the role of ocean circulation in transporting heat to this region," said Yifei Fan, a PhD candidate at Pennsylvania State University and lead author of the research. “Our study, based on observations, quantifies the role of atmospheric circulation change in the cold drop. And that's important because few existing analyzes have focused on the atmospheric circulation that contributes to this long-term change in sea surface temperature," he added.
Despite its anti-global warming appearance, the "cold blob" does not debunk climate change entirely, but rather is a complex manifestation.
Although some studies suggest that this phenomenon may be related to slowing glacier melt in the region, researcher Li is not convinced of a direct connection. Due to the multiple interactions between the atmosphere, ocean, and cryosphere, the relationship between the "cold blob" and Arctic sea ice still requires further study.
Despite its limited range at the ocean surface, the "cold blob" is considered significant due to its location in a critical region for the formation of deep waters and its possible impact on the AMOC, a crucial component of the climate system in the North Atlantic. "It is located in the deep-water formation region that is critical for AMOC, an important heat transport mechanism that maintains habitable climate in the mid-latitudes of the North Atlantic," Li said.
