Origin and evolution of the North Atlantic Oscillation

Area of Science:

• Paleoclimatology
• Atmospheric Science
• Geology

Background:

• The North Atlantic Oscillation (NAO) is a major driver of North Atlantic climate variability.
• Understanding the historical emergence and evolution of the NAO is crucial for climate science.
• Previous research has not fully explored the deep-time origins of the NAO.

Purpose of the Study:

• To determine when the North Atlantic Oscillation (NAO) first emerged.
• To investigate the long-term evolution of the NAO over geological timescales.
• To link the NAO's development to continental drift and orographic changes.

Main Methods:

• Analysis of time-slice paleoclimate simulations.
• Simulations covered the breakup of the supercontinent Pangea, starting 160 million years ago.
• Investigated changes in atmospheric circulation and climate patterns.

Main Results:

• A present-day-like NAO mode gradually formed between 80 and 60 million years ago.
• NAO emergence was driven by North Atlantic Ocean expansion and increased land-ocean contrast.
• This led to a regime transition in Northern Hemisphere winter circulation, including jet stream shifts and strengthened storm tracks.

Conclusions:

• The NAO's evolutionary history is linked to continental evolution and orography.
• The expansion of the North Atlantic Ocean and mountain building significantly influenced NAO development.
• This study provides insights into the long-term dynamics of major climate patterns.