A detailed analysis of deep-decoupling/deep-coupling oscillations in the Welander model

Area of Science:

• Oceanography
• Climate Science
• Geophysics

Background:

• The conceptual Welander model simulates ocean temperature and salinity evolution.
• It uses two vertically stacked boxes representing surface and deep water.
• Interactions occur via diffusion and convective adjustment.

Purpose of the Study:

• To comprehensively study oscillations in the Welander model with smooth, non-instantaneous switching.
• To identify and characterize different oscillation types based on diffusive and convective mixing phases.
• To investigate the impact of gradual freshwater influx on oscillation transitions.

Main Methods:

• Utilized a smooth, non-instantaneous switching function in the Welander model.
• Analyzed parameter space to identify regions for different oscillation types.
• Simulated the effects of gradual freshwater influx on model dynamics.

Main Results:

• Identified four distinct oscillation types based on mixing phases.
• Confirmed that characteristic Welander deep-(de)coupling oscillations persist but require faster switching.
• Demonstrated transitions between oscillation types induced by freshwater influx.

Conclusions:

• Smooth switching functions reveal complex oscillatory behaviors in the Welander model.
• Sustained deep-decoupling oscillations necessitate rapid switching dynamics.
• Freshwater forcing can dynamically alter ocean mixing regimes.