Comparison of SSH anomalies derived from open ocean bottom pressure measurements (from NOAA DART® systems) with multi-satellite merged altimeter missions and coastal tide gauge records

George Mungov (NOAA/NESDIS/NCEI/OGSSD, Boulder, Colorado, United States)


Yongsheng Zhang (NOAA/NESDIS/NCEI/OGSSD, Silver Springs, Maryland, United States)

Event: 2020 Ocean Surface Topography Science Team Meeting (virtual)

Session: Science III: Mesoscale and sub-mesoscale oceanography

Presentation type: Type Forum

The purpose of our study is to investigate the possible application of NOAA DART® (Deep-ocean Assessment and Reporting of Tsunamis) data beyond tsunami research. We compare DART® data with coastal tide gauge observations and satellite altimeter records. DART® systems are designed to measure changes in water column pressure at the ocean floor caused by passing tsunamis and to send the data to tsunami warning centers. DART® in-situ measurements are the only reliable indicator of generated tsunamis and their magnitude.
Today DART® data are used in tsunami research and forecasting employing relatively short time segments lasting from several hours to several days. This study investigates the time scales where DART® observations reliably represent open-ocean water level variations. We compare 17 selected DART® records against merged satellite altimeter and coastal tide gauge observations. DART® ocean bottom pressure measurements are transformed to SSHA using gridded atmospheric pressure data from the NOAA 20th Century Reanalysis project. Altimeter time series as multi-satellite merged sea surface height anomalies (SSHA) are picked from the 1/4 degree gridded optimal interpolated daily sea level anomalies from NOAA archives. Coastal tide gauge records are extracted from NOAA and international sources.
We found that there is a good match between DART® adjusted SSHA and altimeter SSHA and coastal tide gauge records in regions with high atmospheric dynamics. These regions are: the North Pacific Ocean near Japan and the Aleutian Islands and Alaska; around the Hawaii Islands; the West Atlantic off the East Coast of the United States, and the Caribbean Basin. Our findings indicate that in these regions DART® adjusted SSHA characterize the open-ocean water level variations in the frequency band one cycle per 7 to 12 (14) days. For lower frequencies (periods longer than 1 cycle per 12-14 days), DART® systems do not record the long period pressure variations due to BPR container plastic deformations. For frequencies higher than 1 cycle per 5-7 days, local conditions at DART® deployment sites and at the coastal stations are dominating. We suggest that DART® and altimeter records could be used in parallel, as DART® data discover the “fine” or high-frequency components, while altimeter data represent low-frequency components, such as the seasonal cycle.
George Mungov
United States