Microscopic fossil marine algae discovered at high altitudes in the Antarctic ice sheet interior were likely transported there 3 million years ago by strong winds acting in combination with significant ice sheet melt, according to a study in Nature Communications. The findings support the view that parts of the East Antarctic Ice Sheet are vulnerable to relatively modest warming.
The initial discovery of these ancient marine fossils high in the Transantarctic Mountains over 30 years ago sparked a heated debate regarding the stability of the East Antarctic Ice Sheet during the Pliocene (about 3 million years ago). One faction argues that the fossils indicate at least one period of dramatic ice sheet retreat (and thus sea level rise) and the emergence of algae-filled seas in the centre of Antarctica. The opposing faction argues against the extensive ice retreat and the mountain uplift required to transport the algae from these Antarctic seas, instead suggesting that the relatively light algae were more probably transported from the coast by strong winds. The arguments have raged back and forth for three decades.
Reed Scherer and colleagues combine a sophisticated ice-sheet model and a regional climate model to offer an intermediate solution. Although the authors’ results do not support glacier transport of the fossils from the Antarctic interior during the Pliocene, they reveal significant ice retreat around the margins of the East Antarctic Ice Sheet, and the emergence of large algae-rich marine embayments. Their data indicate that the removal of the weight of the ice further leads to uplift of the land and exposure of algae-draped coastal plains and islands to the effects of the wind. The authors’ regional climate model indicates that sufficiently strong wind transport pathways existed during the Pliocene in order to transport these exposed algae high into the ice sheet interior, thus offering an explanation for the algae’s presence, and discovery 3 million years later, in the Transantarctic Mountains.
The Pliocene climate is considered analogous to that predicted for the coming decades to centuries, and as such, these findings could have important implications for future ice sheet melt and sea level rise.