Exceptional Changes in the AMOC During the Industrial Era
Abstract
The Atlantic meridional overturning circulation (AMOC) plays an essential role in climate through its redistribution of heat and its influence on the carbon cycle. Short observational datasets preclude a longer-term perspective on the modern state and variability of AMOC, for which we must therefore use paleoclimate reconstructions. Here, we use sediment grain size analysis and reconstruction of the AMOC surface temperature fingerprint to examine Holocene changes in the AMOC and its constituent components. We reveal that the AMOC has likely been anomalously weak over the past 150 years (since the end of the Little Ice Age, LIA; 1850 CE), and is associated with exceptional surface and deep ocean circulation patterns. We explore differences between various AMOC proxies, as well as constrain Holocene variability in individual AMOC components. The Industrial era weakening was likely caused by the combination of relatively weak Nordic Overflows and Labrador Sea convection. We suggest that enhanced freshwater fluxes from the Arctic and Nordic Seas, towards the end of the LIA, sourced from melting glaciers and thickened sea-ice that had developed earlier throughout the Neoglacial and LIA, led to the exceptional recent AMOC weakening. The lack of a subsequent recovery may result from hysteresis or anthropogenic forcing during the twentieth century. Finally we present productivity related proxies which demonstrate the impact recent AMOC changes have had on ecosystems within the North Atlantic.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMPP14A..04T
- Keywords:
-
- 1616 Climate variability;
- GLOBAL CHANGEDE: 1626 Global climate models;
- GLOBAL CHANGEDE: 4901 Abrupt/rapid climate change;
- PALEOCEANOGRAPHYDE: 4912 Biogeochemical cycles;
- processes;
- and modeling;
- PALEOCEANOGRAPHY