An anomaly in global sea level rise is explained by deep ocean heating

Key Points:

• Climate scientists have long tracked global mean sea level (GMSL) rise by accounting for energy flows causing it, but since 2016, the GMSL "budget" appeared incomplete, missing contributions from deep ocean heat.
• New research published in Earth's Future shows that including heat expansion from ocean depths below 2,000 meters nearly closes the GMSL budget since 2016, attributing about 0.4 mm/year (10%) of sea level rise to deep ocean warming.
• The study relied on combining satellite data, Argo buoy measurements (which only reach 2,000 m), ice sheet and glacier mass balance, and climate reanalysis models to estimate deep ocean heat content, since direct measurements below 2,000 m are limited.
• This finding highlights the growing importance of deep ocean warming in accelerating sea level rise and underscores the need for expanded deep ocean monitoring, such as deploying more Deep Argo buoys.
• Researchers plan to investigate whether recent deep ocean temperature changes are due to natural variability, human-induced climate change, or both, using advanced coupled climate models.