Antarctic Bottom Water (AABW) forms the deepest limb of the meridional
overturning circulation (MOC) and is a key control on global exchanges
of heat, freshwater, and carbon. Density differences that drive the MOC
have their origin, in part, in coastal polynyas. Prydz Bay polynyas in
East Antarctica are a key source of Dense Shelf Water (DSW) that feeds
AABW to the Atlantic and Indian Oceans. However, several poorly
understood mechanisms influence the pathways and change water mass
properties of the DSW on its way to the abyss. To better understand
these mechanisms, we release Lagrangian particles in a 10 km resolution
simulation of the Whole Antarctic Ocean Model and analyze the resulting
tracks using novel cluster analysis. Our results highlight the role of
mixing with other water masses on the shelf in controlling the fate of
DSW and its eventual contribution to AABW. When advected beneath the ice
shelf, DSW can mix with fresh Ice Shelf Water (ISW), becoming less dense
and making future AABW formation less likely. This study confirms that
towards the shelf break along the Antarctic Slope Current, mixing with
circumpolar deep water (CDW) forms modified circumpolar deep water
(mCDW) and influences DSW export as AABW. Our findings indicate that the
pathway from DSW to AABW is sensitive to mixing with ambient waters on
the shelf. An important implication is that with future increase in ice
shelf melt and CDW warming, AABW production is likely to decline, even
if DSW production in coastal polynyas remains constant.