Global decline in ocean memory over the 21st century

Area of Science:

• Climate Science
• Oceanography
• Environmental Science

Background:

• Ocean memory, defined as the persistence of ocean conditions, is a key factor for climate system predictability beyond weather timescales.
• Sea surface temperature (SST) anomalies are a primary indicator of ocean memory.

Purpose of the Study:

• To investigate the projected changes in ocean memory over the coming decades.
• To identify the primary drivers of these changes and their implications for climate prediction and marine resource management.

Main Methods:

• Analysis of year-to-year persistence of sea surface temperature anomalies.
• Modeling the impact of upper-ocean mixed layer depth shoaling due to global surface warming.
• Assessment of regional thermodynamic and dynamic feedback contributions.

Main Results:

• A projected steady decline in global ocean memory over the next decades.
• The primary driver identified as the shoaling of the upper-ocean mixed layer depth due to surface warming.
• Increased effectiveness of stochastic forcing on SST anomalies as the mixed layer shallows, leading to more high-frequency noise.

Conclusions:

• Reduced ocean memory will shorten the lead times for accurate persistence-based predictions of sea surface thermal conditions.
• This decline poses new challenges for predicting climate extremes.
• Management of marine biological resources under climate change may be significantly impacted by these changes in ocean predictability.