Many of Antarctica's ice shelves experience significant surface melting
each season, yet it is generally assumed that nearly all the produced
meltwater re-freezes rather than being lost as runoff. Individual events
of direct surface meltwater loss to the ocean have been documented, but
were thought to be rare. We here present evidence of widespread
through-ice-shelf drainage of supraglacial lakes, observed across
various Antarctic ice shelves. We demonstrate that meltwater can
accumulate for many melt seasons, in lakes that are often covered by an
ice lid. Such buried lakes can drain into the sub ice shelf ocean cavity
nearly instantaneously, creating an ice doline. These doline formation
events are observed year-round and likely occur via a through-cutting
crevasse that propagated from the lake bed by hydrofracture. The removal
of a large load from the top of the floating ice shelf results in
flexural uplift in the region around the drained lake basin. These
surface elevation changes can be monitored using high-resolution
satellite remote sensing data, such as ICESat-2 laser altimetry and
digital elevation models created from WorldView stereo satellite imagery
pairs. We show that doline formation has the potential significantly
change the surrounding ice shelf surface hydrology, leading to different
processes with opposing effects on ice shelf stability. If the surface
depression formed by the former lake bed acts to capture meltwater and
channels it straight down to the ocean via the newly-created drainage
pathway, this process could halt supraglacial meltwater system growth
and thus prevent meltwater from reaching areas more vulnerable to
hydrofracture. However, if flexural uplift diverts meltwater flow around
the doline and delivers it to adjacent areas on the ice shelf surface,
this can lead to repeated hydrofracture in multiple locations and thus
act to destabilize the ice shelf. Which of these mechanisms dominates
over time on each ice shelf may ultimately be crucial for its long-term
resilience in a warming climate.