Southwest Pacific Gyre Dynamics During the Common Era: A New Perspective From Deep-Sea Antipatharians
Abstract
The South Pacific Gyre (SPG) is the largest ocean gyre on earth. It is an integral component of the global climate system, and acts as a critical carbon sink in the global carbon cycle. The SPG modulates heat and marine productivity patterns in the south Pacific through mixing of oligotrophic subtropical waters and nutrient rich subpolar waters. In the southwest Pacific, marine productivity is controlled by seasonal variations in the East Australian Current (EAC).
Recent observations suggest strengthening mid-latitudes westerlies have driven the acceleration of SPG boundary currents, forcing oligotrophic EAC waters further south, creating a climate change 'hotspot' in the southeastern Pacific and decreasing biodiversity and pelagic fishery size. These changes have been attributed to anthropogenic activity, but we lack data on baseline variability: instrumental productivity records only span recent decades and high-latitude paleo-proxies are often too low-resolution to provide insight on anthropogenic timescales. This creates large uncertainties in managing future marine resources and global climate forecasts. Here we present a reconstruction of SPG surface dynamics over the last 3kyr from carbon and nitrogen isotopes (δ13C and δ15N) in three deep-sea Antipatharian corals from New Zealand. Antipatharians live for millennia and their skeletons preserve the isotopic signature of the plankton detritus from the surface. Antipatharian δ13C and δ15N reflect exported surface production, while 14C reservoir age captures mixing of subtropical and subpolar waters. We introduce three annually-decadally resolved reservoir age, δ13C and δ15N reconstructions constrained with 14C and U/Th dates to quantify SPG variability over the last 3kya. Our corals demonstrate highly variable and rapid changes in exported primary production during the late Holocene, potentially driven by anomalous southward EAC penetration during the 2-3kya interval (Komugabe-Dixson et. al, 2016). Our results provide a useful baseline context for modern climate and ocean changes in the south Pacific, and will help inform marine resource management.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMPP43C1948H
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSESDE: 1620 Climate dynamics;
- GLOBAL CHANGEDE: 1630 Impacts of global change;
- GLOBAL CHANGEDE: 4928 Global climate models;
- PALEOCEANOGRAPHY