Sedimentary records of nitrogen isotope in the western tropical Pacific linked to the eastern tropical Pacific denitrification during the last deglacial time

AbstractAn unprecedented extreme positive Indian Ocean Dipole event (pIOD) occurred in 2019, which has caused widespread disastrous impacts on countries bordering the Indian Ocean, including the East African floods and vast bushfires in Australia. Here we investigate the causes for the 2019 pIOD by analyzing multiple observational datasets and performing numerical model experiments. We find that the 2019 pIOD is triggered in May by easterly wind bursts over the tropical Indian Ocean associated with the dry phase of the boreal summer intraseasonal oscillation, and sustained by the local atmosphere-ocean interaction thereafter. During September-November, warm sea surface temperature anomalies (SSTA) in the central-western tropical Pacific further enhance the Indian Ocean’s easterly winds, bringing the pIOD to an extreme magnitude. The central-western tropical Pacific warm SSTA is strengthened by two consecutive Madden Julian Oscillation (MJO) events that originate from the tropical Indian Ocean. Our results highlight the important roles of cross-basin and cross-timescale interactions in generating extreme IOD events. The lack of accurate representation of these interactions may be the root for a short lead time in predicting this extreme pIOD with a state-of-the-art climate forecast model.

Download Full-text

Glider observations of the North Equatorial Current in the western tropical Pacific

Journal of Geophysical Research Oceans ◽

10.1002/2014jc010595 ◽

2015 ◽

Vol 120 (5) ◽

pp. 3586-3605 ◽

Cited By ~ 29

Author(s):

Martha C. Schönau ◽

Daniel L. Rudnick

Keyword(s):

Tropical Pacific ◽

North Equatorial Current ◽

Western Tropical Pacific ◽

The North ◽

Equatorial Current

Download Full-text

Physical forcing and the dynamics of the pelagic ecosystem in the eastern tropical Pacific: simulations with ENSO-scale and global-warming climate drivers

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f03-100 ◽

2003 ◽

Vol 60 (9) ◽

pp. 1161-1175 ◽

Cited By ~ 49

Author(s):

George M Watters ◽

Robert J Olson ◽

Robert C Francis ◽

Paul C Fiedler ◽

Jeffrey J Polovina ◽

...

Keyword(s):

Global Warming ◽

Phytoplankton Biomass ◽

Southern Oscillation ◽

Tropical Pacific ◽

Trophic Levels ◽

Eastern Tropical Pacific ◽

Ecosystem Models ◽

Pelagic Ecosystem ◽

Physical Forcing ◽

Physical Effects

We used a model of the pelagic ecosystem in the eastern tropical Pacific Ocean to explore how climate variation at El Niño Southern Oscillation (ENSO) scales might affect animals at middle and upper trophic levels. We developed two physical-forcing scenarios: (1) physical effects on phytoplankton biomass and (2) simultaneous physical effects on phytoplankton biomass and predator recruitment. We simulated the effects of climate-anomaly pulses, climate cycles, and global warming. Pulses caused oscillations to propagate through the ecosystem; cycles affected the shapes of these oscillations; and warming caused trends. We concluded that biomass trajectories of single populations at middle and upper trophic levels cannot be used to detect bottom-up effects, that direct physical effects on predator recruitment can be the dominant source of interannual variability in pelagic ecosystems, that such direct effects may dampen top-down control by fisheries, and that predictions about the effects of climate change may be misleading if fishing mortality is not considered. Predictions from ecosystem models are sensitive to the relative strengths of indirect and direct physical effects on middle and upper trophic levels.

Download Full-text