Centennial changes in North Pacific anoxia linked to tropical trade winds

Curtis Deutsch; William Berelson; Robert Thunell; Thomas Weber; Caitlin Tems; James McManus; John Crusius; Taka Ito; Timothy Baumgartner; Vicente Ferreira; Jacob Mey; Alexander van Geen

doi:10.1126/science.1252332

USGS · 70115060

Centennial changes in North Pacific anoxia linked to tropical trade winds

Curtis Deutsch·William Berelson·Robert Thunell·Thomas Weber·Caitlin Tems·James McManus·John Crusius·Taka Ito·Timothy Baumgartner·Vicente Ferreira·Jacob Mey·Alexander van Geen

View original source ↗Export metadata ↓

Abstract

Climate warming is expected to reduce oxygen (O 2 ) supply to the ocean and expand its oxygen minimum zones (OMZs). We reconstructed variations in the extent of North Pacific anoxia since 1850 using a geochemical proxy for denitrification (δ 15 N) from multiple sediment cores. Increasing δ 15 N since ~1990 records an expansion of anoxia, consistent with observed O 2 trends. However, this was preceded by a longer declining δ 15 N trend that implies that the anoxic zone was shrinking for most of the 20th century. Both periods can be explained by changes in winds over the tropical Pacific that drive upwelling, biological productivity, and O 2 demand within the OMZ. If equatorial Pacific winds resume their predicted weakening trend, the ocean’s largest anoxic zone will contract despite a global O 2 decline.

Explore related subjects

Science Article

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Curtis Deutsch, William Berelson, Robert Thunell, Thomas Weber, Caitlin Tems, James McManus, John Crusius, Taka Ito, Timothy Baumgartner, Vicente Ferreira, Jacob Mey, Alexander van Geen. 2014. Centennial changes in North Pacific anoxia linked to tropical trade winds. https://doi.org/10.1126/science.1252332

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2026

Forest canopy decline under elevated CO2 during the Paleocene-Eocene Thermal Maximum

Uncertainty remains regarding the impact of rapid anthropogenic warming on forest ecosystem structure, biodiversity, and function. As an analog, we reconstruct forest canopy density and compositional change in Wyoming, USA, through the Paleocene-Eocene Thermal Maximum (PETM), an interval of abrupt carbon increase and warming ~56 million years ago. We develop a proxy to quantify leaf area index and assess shifts in floral composition using palynomorphs. Forest canopies opened abruptly at onset of PETM warming, landscape erosion increased, and vegetation shifted from broad-leaved angiosperm to fern- and palm-dominated ecosystems. When combined with regional data, these patterns suggest that continental-scale changes in plant communities cause landscape destabilization. These shifts also have implications for multimillennial-scale hydrologic and carbon cycle feedbacks in the climate system.

Wyoming↗

USGS2026

Predictable seismic cycles result from structural rupture barriers on oceanic transform faults

Earthquakes of magnitude ( M ) >5.5 on oceanic transform faults (OTFs) repeatedly rupture the same locked patches, sometimes quasiperiodically. These patches are separated by “barriers” that halt earthquake propagation and slip mostly aseismically. However, the physical processes governing this systematic behavior remain unclear. We analyzed two barriers along the Gofar transform fault that have arrested ~15 M 6 earthquakes over the past three decades. Ocean bottom seismometer data indicate that the barriers hosted intense microseismicity before the mainshocks and comprise multistrand faults and transtensional stepovers with 100- to 400-m lateral offset. These characteristics contradict earthquake rupture termination models invoking velocity-strengthening friction or large geometric steps and instead point to damage-enhanced porosity and dilatancy-strengthening mechanisms. By isolating rupture segments, the barriers regulate the quasiperiodic recurrence of OTF earthquakes.

Science↗

USGS2026

A 481 m-high landslide-tsunami in a cruise ship-frequented Alaska fjord

Early in the morning of 10 August 2025, a >64 × 10 6 –cubic meter landslide struck Tracy Arm fjord in Alaska. The landslide was preconditioned by glacial retreat caused by climate change. The resulting 481-meter runup megatsunami followed an initial 100-meter-high breaking wave traveling at >70 meters per second. The landslide was preceded by several days of microseismicity, which increased in rate and magnitude until ~1 hour before failure. The landslide produced globally observed long-period seismic waves equivalent in size to a moment magnitude 5.4 earthquake. A long-period (~66 second) global seismic signal, produced by a landslide-induced seiche trapped within the fjord, persisted for up to 36 hours, the second time a days-long seiche had thus been observed. With fjord regions increasingly visited by cruise ships, and climate change making similar events more likely, this unanticipated, near-miss event highlights the growing risk from landslides and tsunamis in coastal environments.

Alaska↗