The tale of two ice shelves: Zachariae Isstrøm and Nioghalvfjerdsfjorden, Northeast Greenland

Oceanography and gravity data of Northeastern Greenland reveal ocean
temperature and bathymetry in front of Zachariae Isstrøm (ZI) and
Nioghalvfjerdsfjorden (79N), which hold a 1.1-m sea-level rise ice volume
equivalent but underwent different evolutions. Sub-surface, warm, salty
water of Atlantic origin has easier access to ZI than to 79N because of
bathymetric barriers. We reconstruct ice removal by the ocean at the
grounding line and floatation retreat from thinning to explain the
observed grounding line retreat since 1979. The agreement between observed
and calculated retreat demonstrates that ocean thermal forcing is a major
control on the glacier evolution and undercutting of grounded ice must be
included in numerical ice sheet models to reproduce the high rates of
retreat.