GFI/BCCR Seminar: The impact of oceanic near-inertial waves on climate

Markus Jochum (Niels Bohr Institute, Univ. of Copenhagen)

The impact of oceanic near-inertial waves on climate

Abstract

The latest version of the Community Climate System Model (CCSM4) is used to assess the climate impact of wind generated near-inertial waves (NIWs). Even with high-frequency coupling CCSM4 underestimates the strength of NIWs, so that a parameterization for NIWs is developed and included into CCSM4. Numerous assumptions enter this parametrization, the core of which is that the NIW velocity signal is detected during the model integration, and amplified in the shear computation of the ocean surface boundary layer module.

It is found that NIWs deepen the ocean mixed layer by up to 30%, but they contribute little to the ventilation and mixing of the ocean below the thermocline. However, the deepening of the tropical mixed layer by NIWs leads to a change in tropical sea surface temperature and precipitation. Atmospheric teleconnections then change the global sea level pressure fields so that the mid-latitude westerlies become weaker.