Udintsev Fracture Zone observational program to study Antarctic Circumpolar Current near Udintsev Fracture Zone using IESs

Cross-Frontal Fluxes in the Antarctic Circumpolar Current near Udintsev Fracture Zone

Principal Investigators: D. Randolph Watts and Kathleen Donohue

Across the Antarctic Circumpolar Current (ACC), fluxes of heat and momentum and other dynamical quantities establish the heat budget for the whole Southern Ocean, govern the strength of the ACC and its vital inter-ocean exchanges, and arguably govern the main vertical density structure of the world oceans. Yet, theoretical concepts, numerical models, and the sparse observational records give conflicting views of the mechanisms and magnitude of transfers across the ACC. South of about 55°S the puzzle is further confounded, because the heat fluxes associated with wind-driven Ekman transport and its counterbalancing meridional overturning circulation, that are strong and dominant at lower latitudes, become weak. At that latitude, it falls to cross-frontal processes arising from mean and eddying flow to complete the heat budget. It is particularly puzzling how fluxes cross the several ocean fronts, e.g., from Subantarctic Front to Polar Front to Southern ACC Front. Observations of heat and momentum fluxes and mixing are vitally needed at additional sites around the ACC to inform global climate modeling efforts. Of particular interest is how the oceanic meridional overturning circulation absorbs and redistributes heat and carbon that is critical to the earth's climate. The Udintsev Fracture Zone has been selected because the three main fronts (Subantarctic Front, Polar Front, and Southern ACC Front) converge closely together as they deflect equatorward where they encounter complex shallower ridges and exhibit strong eddy variability in the lee. Therefore, the Udintsev Fracture Zone emerges as a likely location for mean and eddy fluxes to combine to cross the entire ACC system.

Presentations

Ocean Sciences Meeting, Portland, Oregon, February 2018

Watts, D. R., K. L. Tracey and K. A. Donohue. Role of the Antarctic Circumpolar Current standing meanders in the downstream evolution of thermohaline properties. 305738, 2018. (Abstract)

UFZ is funded by the National Science Foundation under Award Number 1358470.

Disclaimer: Any opinions, findings and conclusions or recomendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation (NSF).