Exchange of water between the Ross Gyre and ACC assessed by Lagrangian particle tracking

To reach upwelling and downwelling zones deep within the Southern Ocean seasonal sea ice cover, water masses must move across the Antarctic Circumpolar Current and through current systems including the Ross Gyre, Weddell Gyre, and Antarctic Slope Current. In this study we focus our attention on the Lagrangian exchange between the Ross Gyre and surrounding current systems. We conducted numerical experiments using five-day 3-D velocity fields from the Southern Ocean State Estimate with a particle tracking package to identify pathways by which waters move from near the Antarctic coastal margins or Antarctic Circumpolar Current into the interior of the Ross Gyre, and to identify the time scales of variability associated with these pathways. Waters from near the Antarctic margins enter the Ross Gyre along the western and northern boundaries of gyre until the gyre separates from the Pacific-Antarctic Ridge near fracture zones. At this juncture, Antarctic Circumpolar Current-derived inflow dominates the across-gyre transport up to the Antarctic margin. Transport and exchange associated with different time-average components of flow are calculated to determine the relative contributions of high- and low-frequency and time-mean components.