New research led by University College London (UCL) and Woods Hole Oceanographic Institution (WHOI) provides evidence that a key cog in the global ocean circulation system hasn’t been running at peak strength since the mid-1800s and is currently at its weakest point in the past 1,600 years. If the system continues to weaken, it could disrupt weather patterns from the United States and Europe to the African Sahel, and cause more rapid increase in sea level on the U.S. East Coast.