USAP-DC

Part 1: Because of the manner in which it is formed at high latitudes in the Antarctic ice, Antarctic Bottom Water (AABW) is the coldest, saltiest and densest water on the planet. The global circulation of is often quantified via the transport in a two-dimensional, latitude/depth coordinate space. However, AABW formation, northward flow and distribution between the Atlantic, Indian and Pacific basins are fundamentally three-dimensional processes. AABW is formed in a handful of distinct sites around the Antarctic coast, notably the southern Weddell Sea, the western Ross Sea, along the Ad´elie coast, and in Prydz Bay. AABW is one of the key components of the global ocean overturning circulation, and plays a critical role in regulating Earth's climate, on multi-decadal-to-millennial time scales. Part 2: Mapping of AABW transport to northern basins is not well constrained, with conflicting conclusions drawn in previous studies. At one extreme the ACC has been suggested to be a “conduit" that simply allows each variety of AABW to transit directly northward. At the other extreme, it has been suggested that the ACC “blends" all shelf AABW sources together before they reach the northern basins. To close the gap in understanding, this collaborative project draws on three complementary analytical tools: process-oriented modeling of AABW export across the ACC, a high-resolution global ocean model, and an observationally-constrained estimate of the global circulation. The proposed identification and mechanistic understanding of AABW pathways. This project will also advance the careers of three postdoctoral researchers and two early-career faculty members, and will continue collaborative links between the PI and a foreign investigator. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Person	Role
Stewart, Andrew	Investigator and contact
Thompson, Andrew	Investigator
Purkey, Sarah	Investigator

Antarctic Ocean and Atmospheric Sciences	Award # 2023303
Antarctic Ocean and Atmospheric Sciences	Award # 2023259
Antarctic Ocean and Atmospheric Sciences	Award # 2023244

USAP-2023244_1

None in the Database

Repository	Title (link)	Format(s)	Status
USAP-DC	Ocean CFC reconstructed data product	Not Provided	exists
Figshare (open repository)	Code for reproducing the ocean-biogeochemical experiments in Sun et al. (2024)	None	exists
NOAA's National Centers for Environmental Information (NCEI)	Hydrographic data collected from the Bellingshausen and Amundsen seas (NCEI Accession 0210639)	None	exists

1. Stewart, A. L., Chi, X., Solodoch, A., & Hogg, A. M. (2021). High‐Frequency Fluctuations in Antarctic Bottom Water Transport Driven by Southern Ocean Winds. Geophysical Research Letters, 48(17). (doi:10.1029/2021gl094569)
2. Wilson, E. A., Thompson, A. F., Stewart, A. L., & Sun, S. (2022). Bathymetric Control of Subpolar Gyres and the Overturning Circulation in the Southern Ocean. Journal of Physical Oceanography, 52(2), 205–223. (doi:10.1175/jpo-d-21-0136.1)
3. Stewart, A. L., Neumann, N. K., & Solodoch, A. (2023). “Eddy” Saturation of the Antarctic Circumpolar Current by Standing Waves. Journal of Physical Oceanography, 53(4), 1161–1181. (doi:10.1175/jpo-d-22-0154.1)
4. Cimoli, L., Gebbie, G., Purkey, S. G., & Smethie, W. M. (2023). Annually resolved propagation of CFCs and SF6 in the global ocean over eight decades. Journal of Geophysical Research: Oceans, 128, e2022JC019337. (doi:10.1029/2022JC019337)
5. Stewart, A. L., McWilliams, J. C., & Solodoch, A. (2021). On the Role of Bottom Pressure Torques in Wind-Driven Gyres. Journal of Physical Oceanography, 51(5), 1441–1464. (doi:10.1175/jpo-d-20-0147.1)
6. Si, Y., Stewart, A. L., & Eisenman, I. (2022). Coupled ocean–sea ice dynamics of the Antarctic Slope Current driven by topographic eddy suppression and sea ice momentum redistribution. Journal of Physical Oceanography, 52(7), 1563-1589. (doi:10.1175/JPO-D-21-0142.1)
7. Solodoch, A., Stewart, A. L., McC. Hogg, A., & Manucharyan, G. E. (2023). Machine Learning‐Derived Inference of the Meridional Overturning Circulation From Satellite‐Observable Variables in an Ocean State Estimate. Journal of Advances in Modeling Earth Systems, 15(4), e2022MS003370. (doi:10.1029/2022MS003370)
8. Si, Y., Stewart, A. L., & Eisenman, I. (2023). Heat transport across the Antarctic Slope Front controlled by cross-slope salinity gradients. Science advances, 9(18), eadd7049. (doi:10.1126/sciadv.add7049)
9. Moorman, R., Thompson, A.F. Wilson, E.A. (2023). Coastal polynyas enable transitions between high and low West Antarctic ice shelf melt rates. Geophysical Research Letters, 50, e2023GL104724. (doi:10.1029/2023GL104724)
10. Schmidgall, C.R., Si, Y., Stewart, A.L., Thompson A.F. & Hogg A.McC (2023). Dynamical controls on bottom water transport and transformations across the Antarctic Circumpolar Current, Journal of Physical Oceanography, 53, 1917-1940. (doi:10.1175/JPO-D-22-0113.1)
11. Prend, C.J., MacGilchrist, G.A., Manucharyan, G.E., Pang, R.Q., Moorman, R., Thompson, A.F., Griffies, S.M., Mazloff, M.R., Talley, L.D. & Gille, S.T. (2024). Ross Gyre variability modulates oceanic heat supply to the West Antarctic continental shelf. Communications Earth & Environment, 5, 47. (doi:10.1038/s43247-024-01207-y)
12. Sun, S., Thompson, A.F., Yu, J. & Wu, L. (2024). Transient overturning changes cause upper-ocean nutrient decline in a warming climate. Nature Communications, 15, 7727. (doi:10.1038/s41467-024-52200-0)
13. Flexas, M., Thompson, A.F., Robertson, M.L., Speer, K., Sheehan, P. & Heywood, K.J. (2024). Pathways of inter-basin exchagne from the Bellingshausen Sea to the Amundsen Sea. Journal of Geophysical Research Oceans, 129, e2023JC020080. (doi:10.1029/2023JC020080)