- Mar 2021
“That was not predicted,” said Joel Hirschi, principal scientist at the centre and senior author of the research. It highlights how current seasonal forecasting models are unable to predict these warm summers. And it underscores the paradox that, far from ushering in a frigid future for, say, Paris, a cooler North Atlantic might actually make France’s summers more like Morocco’s.
As in the paragraph above, here the long-term warming hole has been conflated with the short-term North Atlantic cold anomaly, which are phenomena with very different timescales and causes.
Predicting future short-term North Atlantic cold anomalies and subsequent possible heat waves would be done using seasonal forecasting models. Predicting the longer-term impacts of an AMOC slowdown would be done using climate models run under different emissions scenarios.
Conflating the two mechanisms and timescales has resulted in some confusion in this part of the article.
Scientists at the U.K.’s National Oceanography Centre have somewhat counterintuitively linked the cold blob in the North Atlantic with summer heat waves in Europe. In 2015 and 2018, the jet stream, a river of wind that moves from west to east over temperate latitudes in the northern hemisphere, made an unusual detour to the south around the cold blob. The wrinkle in atmospheric flow brought hotter-than-usual air into Europe, they contend, breaking temperature records.
Here, the decadal-scale warming hole that is possibly linked to AMOC slowdown has been conflated with the shorter-term cold anomaly that featured record low North Atlantic sea surface temperatures in 2015.
The authors of the NOC study are careful to make this distinction in their article:
It is important to distinguish between this long-term warming hole and the short-term 2015 cold anomaly that is the focus of our study.
The long-term warming hole that is the focus of this New York Times article is not the same thing as the short-term 2015 cold anomaly. The two phenomena have very different timescales and different causes. Current understanding suggests that the short-term 2015 cold anomaly was caused by successive winters with extreme heat loss, i.e. it was largely driven by changes in air-sea heat exchange. The longer-term warming hole may have been caused by the AMOC slowdown, as discussed in this article.
For more information on the 2015 cold anomaly and its causes, see this review article led by Simon Josey.
- Aug 2017
Global Ocean Circulation Appears To Be Collapsing Due To A Warming Planet
I'm a little hesitant about the title. The slowdown of the Atlantic Meridional Overturning Circulation is not the same thing as the "collapse of global ocean circulation". It might be more accurate to say that the AMOC is at risk of collapsing in a warming world.
Also, it's worth noting that although we understand that there is a connection between AMOC and the amount of carbon dioxide in the atmosphere, the mechanisms involved in this connection are still under investigation.
This link appears to go to an irrelevant article. Here are two relevant articles on the "warming hole":
Evidence is growing that the comparatively cold zone within the Northern Atlantic could be due to a slowdown of this global ocean water circulation.
For example, this study (Rahmstorf et al, 2015):