Impact of Recent Westerly Wind Trends on the Southern Ocean.

The currents of the Southern Ocean have a major impact on the biology and chemistry in the oceans, the formation of Antarctic sea-ice, and the transfer of heat and carbon from the atmosphere into the oceans, regulating Earth’s climate. The strong near-surface atmospheric winds that blow across the southern hemisphere play a key role in causing the flow within the Southern and neighboring oceans. Observations have shown substantial changes in these winds over the last four decades, including a strengthening and movement towards the south pole of the peak winds at the end of the twentieth century, that has paused since 2000. Given the known linkages between winds and ocean flow it is reasonable to anticipate that the observed wind trends will lead, or have already led, to changes in Southern Ocean trends. However, this has not yet been examined in detail. This project will address the knowledge gap by quantifying the impact the recent wind pauses and regional variations in wind trends on the Southern Ocean. This project will provide training for an AGU Bridge program graduate student and for several undergraduate students, incorporate findings into lesson plans, engage with local Baltimore City schools through informal outreach activities and summer camps, and broaden participation in the geosciences by building on existing NSF GEOPaths projects. This research will improve our understanding of the response of the Southern Ocean to temporal and regional variations in southern hemisphere wind stresses using a combination of ocean and climate model simulations together with observations. Idealized simulations with abrupt changes in the wind and buoyancy forcing will be analyzed to quantify the magnitude and time scales of the response of the Southern Ocean to changes in westerly winds. Researchers will then use simulations forced by observed atmospheric changes and ocean observations to quantify how much of the recent changes in the Southern Ocean can be explained by trends in the winds. Addressing key knowledge gaps with new diagnostics applied to next-generation ocean and climate models will improve our understanding of the causes of recent changes in the Southern Ocean and their impact on Antarctic and global climate. It will also provide insights into future changes, both near and long-term, when weak trends in the zonal winds are expected as the ozone hole slowly recovers, and later in the century when wind changes will likely depend on the balance between stratospheric ozone recovery and continued increases in greenhouse gases. 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.