Publication Date:
2017-12-15
Description:
Warm water of open ocean origin on the continental shelf of the Amundsen and Bellingshausen Seas
causes the highest basal melt rates reported for Antarctic ice shelves with severe consequences for the ice
shelf/ice sheet dynamics. Ice shelves fringing the broad continental shelf in the Weddell and Ross Seas melt
at rates orders ofmagnitude smaller. However, simulations using coupled ice–ocean models forced with the
atmospheric output of the HadCM3 SRES-A1B scenario run (CO2 concentration in the atmosphere reaches
700 ppmv by the year 2100 and stays at that level for an additional 100 years) show that the circulation
in the southern Weddell Sea changes during the twenty-first century. Derivatives of Circumpolar Deep
Water are directed southward underneath the Filchner–Ronne Ice Shelf, warming the cavity and dramatically
increasing basal melting. To find out whether the open ocean will always continue to power the
melting, the authors extend their simulations, applying twentieth-century atmospheric forcing, both alone
and together with prescribed basal mass flux at the end of (or during) the SRES-A1B scenario run. The
results identify a tipping point in the southern Weddell Sea: once warm water flushes the ice shelf cavity a
positive meltwater feedback enhances the shelf circulation and the onshore transport of open ocean heat.
The process is irreversible with a recurrence to twentieth-century atmospheric forcing and can only be
halted through prescribing a return to twentieth-century basal melt rates. This finding might have strong
implications for the stability of the Antarctic ice sheet.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Article
,
isiRev
,
info:eu-repo/semantics/article
Format:
application/pdf
