"First, they should construct them in the outlet fjords of Greenland’s largest glaciers, like Jakobshavn. These fjords are often only a mile or two wide, and an

"First, they should construct them in the outlet fjords of Greenland’s largest glaciers, like Jakobshavn. These fjords are often only a mile or two wide, and an underwater dredging project there would resemble successful large-scale civil engineering projects, like the Palm Islands in Dubai. Greenland is also under the shared control of Denmark and the Greenlandic national government, two entities that might decide to undertake the construction project together." Even if the later stages (building 60-mile-long sills beneath floating ice) seem unlikely to be cost-efficient, this part definitely sounds like it could be feasible; It's especially notable to me amongst climate-related megaprojects in that it does not require any new developments, but rather uses extant, mature technologies. Building the sills would require "only" time and money.