A new-generation internal tide model based on 30 years of satellite sea surface height measurements: multiwave decomposition and isolated beams
Year: 2025
Type: article
Abstract: A new-generation internal tide model ZHAO30yr is constructed using 30 years of sea surface height measurements from 1993 to 2022 made by 15 satellite altimetry missions. The model contains 8 mode-1 constituents (M2, S2, N2, K2, K1, O1, P1 and Q1) and 4 mode-2 constituents (M2, S2, K1 and O1). These constituents are respectively extracted by the same mapping technique that consists of two rounds of plane wave analysis with a spatial bandpass filter in between. Their prerequisite wavelengths are calculated from climatological annual-mean hydrographic profiles in the World Ocean Atlas 2018. Model errors are estimated to be 0.5-1 mm for all semidiurnal and diurnal constituents. The model is evaluated using 1 year of independent altimetry data in 2023. The global internal tide field is decomposed into multiconstituent multimodal multidirectional internal waves. Multiwave decomposition reveals unprecedented new features previously masked by multiwave interference. Numerous long-range internal tidal beams are observed to be associated with notable topographic features. Semidiurnal beams off the Amazon shelf and diurnal beams in the Arabian Sea are studied in detail. The M2 and K1 internal tide constituents are examined for their multiwave decomposition and isolated beams on a global scale.
Source: Earth system science data
Author: Zhongxiang Zhao
Language: English
Subfield: Oceanography
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,509
Awards: SATELLITE ALTIMETRY IS THE ONLY PRACTICAL TECHNIQUE FOR MAPPING INTERNAL TIDES ON A GLOBAL SCALE. HOWEVER THE TRADITIONAL POINT-WISE HARMONIC ANALYSIS HAS ITS INHERENT LIMITATIONS IN EXTRACTING INTERNAL TIDES FROM SATELLITE ALTIMETER DATA BECAUSE OF THE COMPLEX NATURE OF THE GLOBAL INTERNAL TIDE FIELD AND MESOSCALE CONTAMINATION. WE HAVE DEVELOPED A PLANE WAVE FIT METHOD TO ADDRESS THIS CHALLENGE. IN THIS METHOD INTERNAL TIDES ARE EXTRACTED USING DATA IN A FITTING WINDOW (ABOUT ONE WAVELENGTH) RATHER THAN AT ONE SINGLE SITE. THIS MAPPING TECHNIQUE IS SUPERIOR TO POINT-WISE HARMONIC ANALYSIS FOR THE FOLLOWING REASONS: FIRST IT SEPARATELY RESOLVES INTERNAL TIDAL WAVES WITH DIFFERENT PROPAGATION DIRECTIONS; SECOND IT SUPPRESSES MESOSCALE CONTAMINATION BY EXTRACTING INTERNAL TIDES WITH BOTH SPATIAL AND TEMPORAL COHERENCE. TAKING ADVANTAGE OF 20 YEARS OF MULTISATELLITE SSH MEASUREMENTS WE HAVE CONSTRUCTED GLOBAL MAPS OF M2 S2 O1 AND K1 INTERNAL TIDES. RECENTLY WE HAVE MADE SIGNIFICANT PROGRESS IN EXAMINING THE TEMPORAL VARIABILITY OF THE INTERNAL TIDE FIELD. WE DIVIDE THE MULTIYEAR ALTIMETER DATA INTO SMALL TIME WINDOWS. THIS ENABLES US TO CONSTRUCT YEARLY INTERNAL TIDE FIELDS FROM 1995 ONWARD. THIS ANALYSIS WILL LEADS TO THE NEXT-GENERATION INTERNAL TIDE MODEL IN WHICH THE AMPLITUDE AND PHASE ARE TIME VARIABLES. THE TRAVEL TIME CHANGES OF INTERNAL TIDES ARE AFFECTED BY THE UPPER OCEAN WARMING. THUS WE BRING UP A NEW CONCEPT OF INTERNAL TIDE OCEANIC TOMOGRAPHY (ITOT) TO MONITOR OCEAN WARMING ON A GLOBAL SCALE. ITOT IS MUCH LIKE ACOUSTIC TOMOGRAPHY (MUNK ET AL. 1995) BUT THAT THE WORK WAVE IS INTERNAL TIDES. ITOT MEASURES OCEAN TEMPERATURE CHANGES BY PRECISELY MEASURING TRAVEL TIME CHANGES OF LONG-RANGE INTERNAL TIDES. ITOT OFFERS A LONG-TERM LOW-COST ENVIRONMENTALLY-FRIENDLY TECHNIQUE FOR MONITORING GLOBAL OCEAN WARMING. MORE RECENTLY WE HAVE EVALUATED THE PERFORMANCE OF OUR INTERNAL TIDE MODEL IN THE CENTRAL NORTH PACIFIC USING 4 YEARS OF CRYOSAT-2 DATA. WE FOUND SIGNIFICANT VARIANCE REDUCTION BEFORE AND AFTER THE M2 INTERNAL TIDE CORRECTION. THE RESULT SUGGESTS THAT OUR INTERNAL TIDE MODEL IS A RELIABLE AND EFFICIENT MODEL. WE PROPOSE TO CONDUCT SUCH KIND OF EXAMINATION ON THE GLOBAL SCALE AND USING DATA FROM OTHER SATELLITES. IN ADDITION IT IS ALSO BENEFICIAL TO INTER-COMPARE INTERNAL TIDE MODELS CONSTRUCTED USING DIFFERENT MAPPING TECHNIQUES. OUR PROPOSED WORK WILL FOCUS ON THE FOLLOWING THREE TOPICS: (1) CONSTRUCTION OF THE NEXT-GENERATION MODEL WITH TIME-VARIABLE AMPLITUDE AND PHASE: (A) CONSTRUCT 20 YEARLY INTERNAL TIDE FIELDS FROM 1995 2014; (B) CONSTRUCT 12 MONTHLY INTERNAL TIDE FIELDS; (C) QUANTIFY THE TEMPORAL VARIATIONS OF AMPLITUDE AND PHASE. (2) DEVELOPMENT OF THE ITOT TECHNIQUE FOR MONITORING GLOBAL OCEAN WARMING: (A) EXAMINE ALONG-BEAM PHASE CHANGES; (B) BUILD TRANSFER FUNCTION FROM SPEED CHANGE RATE TO OCEAN TEMPERATURE CHANGE; (C) CALIBRATE WITH FIELD MEASUREMENTS (E.G. ARGO XBT AND MOORINGS). (3) EVALUATION AND IMPROVEMENT OF OUR INTERNAL TIDE MODEL: (A) REFINE PARAMETERS IN PLANE WAVE FITTING REGION BY REGION; (B) COMPARE WITH OTHER ALTIMETER-BASED INTERNAL TIDE MODELS; (C) EVALUATE OUR MODEL USING ALTIMETER DATA FROM OTHER SATELLITES. THIS PROPOSAL ECHOES THE OSTST SOLICITATION OF NASA AS FOLLOWS. (1) THIS PROPOSAL UTILIZES OVER 20 YEARS OF MULTISATELLITE ALTIMETER DATA (T/P JASON-1/2 ERS-1/2 ENVISAT AND GFO) TO CONSTRUCT THE NEXT-GENERATION INTERNAL TIDE MODEL. MEANWHILE ALTIMETER DATA FROM OTHER SATELLITES (CRYOSAT-2 ALTIKA AND SENTINEL-3) WILL BE USED TO EVALUATE OUR INTERNAL TIDE MODEL. (2) OUR INTERNAL TIDE MODEL MAY BE USED TO CORRECT INTERNAL TIDE SIGNALS IN SWOT AS WELL AS PREVIOUS NADIR-LOOKING ALTIMETER MISSIONS. (3) THE PROPOSED ITOT TECHNIQUE CAN INFER THE SEA LEVEL RISE CAUSED BY HYDROSTATIC THERMAL EXPANSION SEPARATED FROM CONTRIBUTION OF MELTING ICE. ITOT SUPPORTS NASA'S OPERATION AND APPLICATION OF ALTIMETER SATELLITES., Global Internal Tide Model from Satellite Altimetry by Resolving Multiconstituent Multimodal Multidirectional Waves
OpenAlex ID: W4413297168