The Gulf Stream, part of the Atlantic Meridional Overturning Circulation, carries warm tropical water northward along the European coast, significantly moderating winter temperatures in Denmark and Norway—without it, these regions would be as cold as similarly-positioned areas in Canada. However, this warming effect could weaken or even collapse in the coming decades. Climate change is causing Greenland’s ice sheet to melt, adding massive amounts of fresh water to the North Atlantic, which disrupts the density-driven currents that power the Gulf Stream system. If the Gulf Stream were to substantially weaken, Northern Europe could experience much harsher winters, disrupted weather patterns, and altered rainfall, while the shift would also affect global ocean heat distribution and sea levels, with potentially severe consequences for ecosystems and human societies worldwide.