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WE PROPOSE TO INVESTIGATE THE ROLE OF SUBANTARCTIC MODE WATER (SAMW) AND ANTARCTIC INTERMEDIATE WATER (AAIW) IN DETERMINING THE MAGNITUDE AND VARIABILITY OF SOUTHERN OCEAN CARBON UPTAKE. THE RECENT AVAILABILITY OF VERTICALLY RESOLVING BIOGEOCHEMICAL PROFILING FLOATS IN THE SOUTHERN OCEAN HAS DRAMATICALLY INCREASED THE NUMBER AND SPATIAL COVERAGE OF OBSERVATIONS THROUGHOUT THE ANNUAL CYCLE. THESE OBSERVATIONS COMBINED WITH SATELLITE OBSERVATIONS AND THE ECCO-DARWIN STATE ESTIMATE NOW PROVIDE A SIGNIFICANT NEW OPPORTUNITY TO IMPROVE OUR UNDERSTANDING OF THE MECHANISMS MAGNITUDE SEASONAL CYCLE AND VARIABILITY OF AIR-SEA CO2 FLUXES IN THIS REGION. WE WILL ADDRESS THE FOLLOWING GOALS: A. CHARACTERIZE SAMW AND AAIW BIOGEOCHEMICAL PROPERTIES AT THE TIME OF FORMATION AND DETERMINE THE MIXED LAYER PROCESSES THAT PLAY AN IMPORTANT ROLE IN SETTING THOSE PROPERTIES PRIOR TO SUBDUCTION INTO THE OCEAN INTERIOR B. DESCRIBE AND QUANTIFY THE PROCESSES THAT PLAY AN IMPORTANT ROLE IN GOVERNING CARBON ACCUMULATION AND OTHER BIOGEOCHEMICAL CHANGES TO SUBDUCTED SAMW AND AAIW BETWEEN INITIAL FORMATION AND PRIOR TO EXPORT FROM THE SOUTHERN OCEAN C. DETERMINE THE SPATIAL AND TEMPORAL INTERANNUAL VARIABILITY IN FORMATION PROPERTIES CARBON UPTAKE AND HOW THEY RELATE TO SURFACE FORCINGS SUCH AS WIND SPEED SEA ICE FRESHWATER FLUX HEAT FLUXES AND LARGER VARIABILITY ASSOCIATED WITH ENSO AND SAM WE HYPOTHESIZE SAMW AND AAIW ACQUIRE LITTLE CARBON THROUGH DIRECT AIR-SEA GAS EXCHANGE DURING THE WINTER FORMATION PERIOD. OUR PRELIMINARY RESULTS SUGGEST THESE WATER MASSES HAVE AN EXCESS OF CO2 RELATIVE TO THE ATMOSPHERE WHEN THEY FORM. ADDITIONALLY WE HYPOTHESIZE THAT INTERIOR OCEAN MIXING OF BIOGEOCHEMICAL PROPERTIES WITHIN SAMW AND AAIW AND WATER MASS TRANSFORMATION OF SAMW AND AAIW BY DIAPYCNAL MIXING WILL BE OF GREATER IMPORTANCE IN SETTING EXPORTED BIOGEOCHEMICAL PROPERTIES THAN INITIAL SURFACE AIR-SEA FLUXES. WE FURTHER HYPOTHESIZE THAT SAMW WILL EXHIBIT SIMILAR VARIABILITY IN BIOGEOCHEMICAL PROPERTIES AS IT DOES IN PHYSICAL PROPERTIES WITH AN APPROPRIATE LAG FOR AIR-SEA GAS EXCHANGE. THE PROPOSED WORK ADDRESSES NASA ROSES A.5 CARBON CYCLE SCIENCE TOPIC 3.2.2 CARBON FLUXES BETWEEN OCEANS AND THE ATMOSPHERE BY ADVANCING OUR UNDERSTANDING OF OCEAN CARBON UPTAKE MAGNITUDE MECHANISMS PATTERN AND VARIABILITY. THE WORK ALSO ADDRESSES TOPIC 3.1.3 FLUXES AND BIOGEOCHEMISTRY OF CARBON WITHIN OCEANS BY IMPROVING OUR UNDERSTANDING OF CARBON STORAGE IN MODE WATERS THROUGH VALIDATION AND ANALYSIS OF ECCO USING FLOAT OBSERVATIONS AND THEREBY INCREASING OUR ABILITY TO MODEL FUTURE CHANGES IN SOUTHERN OCEAN CARBON STORAGE.

$810,461FY2022National Aeronautics and Space AdministrationNASA

University Of Hawaii, Honolulu

Investigators

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WE PROPOSE TO INVESTIGATE THE ROLE OF SUBANTARCTIC MODE WATER (SAMW) AND ANTARCTIC INTERMEDIATE WATER (AAIW) IN DETERMINING THE MAGNITUDE AND VARIABILITY OF SOUTHERN OCEAN CARBON UPTAKE. THE RECENT AVAILABILITY OF VERTICALLY RESOLVING BIOGEOCHEMICAL PROFILING FLOATS IN THE SOUTHERN OCEAN HAS DRAMATICALLY INCREASED THE NUMBER AND SPATIAL COVERAGE OF OBSERVATIONS THROUGHOUT THE ANNUAL CYCLE. THESE OBSERVATIONS COMBINED WITH SATELLITE OBSERVATIONS AND THE ECCO-DARWIN STATE ESTIMATE NOW PROVIDE A SIGNIFICANT NEW OPPORTUNITY TO IMPROVE OUR UNDERSTANDING OF THE MECHANISMS MAGNITUDE SEASONAL CYCLE AND VARIABILITY OF AIR-SEA CO2 FLUXES IN THIS REGION. WE WILL ADDRESS THE FOLLOWING GOALS: A. CHARACTERIZE SAMW AND AAIW BIOGEOCHEMICAL PROPERTIES AT THE TIME OF FORMATION AND DETERMINE THE MIXED LAYER PROCESSES THAT PLAY AN IMPORTANT ROLE IN SETTING THOSE PROPERTIES PRIOR TO SUBDUCTION INTO THE OCEAN INTERIOR B. DESCRIBE AND QUANTIFY THE PROCESSES THAT PLAY AN IMPORTANT ROLE IN GOVERNING CARBON ACCUMULATION AND OTHER BIOGEOCHEMICAL CHANGES TO SUBDUCTED SAMW AND AAIW BETWEEN INITIAL FORMATION AND PRIOR TO EXPORT FROM THE SOUTHERN OCEAN C. DETERMINE THE SPATIAL AND TEMPORAL INTERANNUAL VARIABILITY IN FORMATION PROPERTIES CARBON UPTAKE AND HOW THEY RELATE TO SURFACE FORCINGS SUCH AS WIND SPEED SEA ICE FRESHWATER FLUX HEAT FLUXES AND LARGER VARIABILITY ASSOCIATED WITH ENSO AND SAM WE HYPOTHESIZE SAMW AND AAIW ACQUIRE LITTLE CARBON THROUGH DIRECT AIR-SEA GAS EXCHANGE DURING THE WINTER FORMATION PERIOD. OUR PRELIMINARY RESULTS SUGGEST THESE WATER MASSES HAVE AN EXCESS OF CO2 RELATIVE TO THE ATMOSPHERE WHEN THEY FORM. ADDITIONALLY WE HYPOTHESIZE THAT INTERIOR OCEAN MIXING OF BIOGEOCHEMICAL PROPERTIES WITHIN SAMW AND AAIW AND WATER MASS TRANSFORMATION OF SAMW AND AAIW BY DIAPYCNAL MIXING WILL BE OF GREATER IMPORTANCE IN SETTING EXPORTED BIOGEOCHEMICAL PROPERTIES THAN INITIAL SURFACE AIR-SEA FLUXES. WE FURTHER HYPOTHESIZE THAT SAMW WILL EXHIBIT SIMILAR VARIABILITY IN BIOGEOCHEMICAL PROPERTIES AS IT DOES IN PHYSICAL PROPERTIES WITH AN APPROPRIATE LAG FOR AIR-SEA GAS EXCHANGE. THE PROPOSED WORK ADDRESSES NASA ROSES A.5 CARBON CYCLE SCIENCE TOPIC 3.2.2 CARBON FLUXES BETWEEN OCEANS AND THE ATMOSPHERE BY ADVANCING OUR UNDERSTANDING OF OCEAN CARBON UPTAKE MAGNITUDE MECHANISMS PATTERN AND VARIABILITY. THE WORK ALSO ADDRESSES TOPIC 3.1.3 FLUXES AND BIOGEOCHEMISTRY OF CARBON WITHIN OCEANS BY IMPROVING OUR UNDERSTANDING OF CARBON STORAGE IN MODE WATERS THROUGH VALIDATION AND ANALYSIS OF ECCO USING FLOAT OBSERVATIONS AND THEREBY INCREASING OUR ABILITY TO MODEL FUTURE CHANGES IN SOUTHERN OCEAN CARBON STORAGE. · GrantIndex