Study finds Atlantic Ocean circulation weakening A new study has worrying conclusions about changes to a vital aspect of the global climate system. Why it matters: The apparent weakening of the Atlantic Meridional Overturning Circulation (AMOC) — largely because of melting ice — is a reminder that climate change could bring about nasty surprises in the future. Nature Geoscience on Thursday, researchers reported the AMOC — a system of ocean currents that includes the Florida Current and the Gulf Stream — is in its "weakest state in over a millennium." The AMOC is the oceans' thermohaline circulation, and it plays an important role in managing the global climate, including keeping temperatures in Europe warmer than they would otherwise be for its latitude.