Low-Frequency Dynamic Ocean Response to Barometric-Pressure Loading

Changes in dynamic manometric sea level zm represent mass-related sea level changes associated with ocean circulation and climate. A study co-authored by AER scientists Rui Ponte and Mengnan Zhao uses twin model experiments to quantify magnitudes and spatiotemporal scales of zm variability caused by barometric pressure pa loading at long periods ( 1 month) and large scales ( 300 km) relevant to Gravity Recovery and Climate Experiment (GRACE) ocean data. Loading by pa drives basin-scale monthly zm variability with magnitudes as large as a few centimeters. Largest zm signals occur over abyssal plains, on the shelf, and in marginal seas. Correlation patterns of modeled zm are determined by continental coasts and H/f contours (H is ocean depth and f is Coriolis parameter). On average, zm signals forced by pa represent departures of  10% and  1% from the inverted barometer effect zib on monthly and annual periods, respectively. Basic magnitudes, spatial patterns, and spectral behaviors of zm from the model are consistent with scaling arguments from barotropic potential vorticity conservation. The study also compares  zm from the model driven by pa to zm from GRACE observations. Modeled and observed zm are significantly correlated across parts of the tropical and extratropical oceans, on shelf and slope regions, and in marginal seas. Ratios of modeled to observed zm magnitudes are as large as ∼0.2 (largest in the Arctic Ocean) and qualitatively agree with analytical theory for the gain of the transfer function between zm forced by pa and wind stress. Results demonstrate that pa loading is a secondary but nevertheless important contributor to monthly mass variability from GRACE over the ocean.

Fig 1 resized.jpg

Figure 1 -  Standard deviation of manometric sea level in centimeters, estimated from model output for the period 1993-2017

Citation: Low-Frequency Dynamic Ocean Response to Barometric-Pressure Loading

G. Piecuch, I. Fukumori, R. M. Ponte, M. Schindelegger, O. Wang, M. Zhao

Phys. Ocean., 52, 2627-2641, 2022.


Principal Scientist, Atmosphere, Ocean and Climate

Staff Scientist, AER