WASHINGTON — The internet was abuzz Thursday evening following a report by the Wall Street Journal that President Donald Trump has expressed interest in buying Greenland. By Friday, it had become clear Greenland has no interest in selling, but jokes about penguins, polar bears and climate change kept flying.

But while the idea seemed custom built for the Twitter mockery cycle, the U.S. does have vital national security interests in Greenland, a semi-autonomous part of Denmark — and the region is attracting attention from competitor China as well.

Under a self-rule act passed in 2009, Greenland has control over its domestic infrastructure or economic policy issues, but Denmark maintains veto power on security issues. Even if Denmark was interested in selling Greenland — and it appears they are not — it is likely the government in Nuuk could block it.

However, the U.S. doesn’t really need all of Greenland for strategic reasons, because of the basing agreements it already has, including one of the U.S. military’s most important strategic tracking systems.

Located on the northwestern coast of Greenland, Thule Air Base is the U.S. military’s northernmost base and the only installation north of the Arctic Circle. It is home to the 12th Space Warning Squadron, a cadre of Air Force officers and enlisted personnel that provide 24/7 missile warning and space surveillance using a massive AN/FPS-132 radar.

Thule’s position on the globe and its radar’s 240 degrees of coverage — which projects over the Arctic Ocean and Russia’s northern coast — make it an ideal location to track intercontinental ballistic missiles and satellites in low-Earth orbit, including polar orbit satellites.

Besides being a critical site for missile defense and space situational awareness, Thule hosts the Defense Department’s northernmost deep-water seaport and airfield. Those assets would come into play in any sort of military conflict in the arctic, giving the Pentagon forward- basing options if needed.

It’s not just America who acknowledges the strategic importance of Greenland, either. Look no further than China, which has repeatedly attempted to gain infrastructure on the island.

In 2016, a Chinese company attempted to buy a former U.S. military base in Greenland, and the government in Denmark stepped in, vetoing the deal. At the time, Danish officials were quoted anonymously in the press, saying they had resisted the deal as a favor to its longtime American ally.

Then in 2018, a Chinese government-owned firm was announced as a likely winner for a contract to build a new airport. The 3.6 billion Danish krone (U.S. $560 million) contract would have given China major economic power over the local government, and decision makers in both Washington and Copenhagen worried it could lead to the U.S. being pushed out of Thule – or give Beijing a ready-made airport that could accommodate Chinese military planes in case of a conflict.

Eventually Copenhagen and Nuuk reached an agreement, with generous financial support from Denmark’s coffers, to pick a different contractor. But it is likely that China will continue to push for entry into Greenland, underlining its strategic importance once again.

Asked if the Pentagon has received any new guidance regarding Greenland, department spokeswoman Lt. Col. Carla Gleason said “Our relationship with the Kingdom of Denmark, of which Greenland is a part, has not changed. We have a long-standing defense relationship, and work together on a wide range of security challenges.”