New studies reveal alarming threats to global ocean currents, ice sheets, and sea levels.

A deep ocean current around Antarctica that has been relatively stable for thousands of years could head for "collapse" over the next few decades due to global warming. Such a sudden shift could affect the planet's climate and marine ecosystems for centuries to come. The loss of nutrient-rich seawater near the surface could damage fisheries. The collapse would also impact a nearby Atlantic Ocean current, known as the Atlantic Meridional Overturning Circulation, which affects weather patterns in the U.S. and Europe. Climate change is to blame for the currents to slow down and potentially collapse.