OCN 780 Seminar | North Atlantic salinity extremes emerge under AMOC slowdown | Iwakiri

Presenter: Dr. Tomoki Iwakiri

Title: North Atlantic salinity extremes emerge under AMOC slowdown

The Atlantic Meridional Overturning Circulation (AMOC) is projected to weaken under anthropogenic warming, yet how climate variability will respond remains unclear. This study explores the potential emergence of new forms of climate variability due to the AMOC transition. We analyze a sustained global warming scenario from CMIP6 and show that AMOC weakening triggers the extreme upper-ocean salinity variability in the North Atlantic, with amplitudes far exceeding historical levels. The variability amplifies as it travels across the basin, linked to a slowdown of the Gulf Stream and sharpened spatial salinity contrast. An idealize, theory-guided model demonstrates that mean state changes promote salinity extremes, with their amplification critically dependent on the salinity–temperature coupled mode. Once the AMOC slowdown is underway, enhanced variability can arise even under a CO 2 removal scenario, implying that amplification of salinity variability is unavoidable despite climate mitigation efforts. Furthermore, this salinity variability contributes to sea surface height increases, driving compound extremes of salinity and sea surface height, and potentially impacting the European coast.

Location: MSB-100

Time: 3:00 pm to 4:15 pm