Geophysical Research Letters最新文献

The mechanisms by which ongoing climate change influences ocean Oxygen Minimum Zones (OMZs) are insufficiently understood, making it essential to examine their long-term variations under substantial climatic forcing. Here, we present the first planktic foraminifera iodine-to-calcium records in two Arabian Sea sediment cores: one located within the core of the modern OMZ in the north and other on its southeastern flank, enabling us to infer the lateral extent of the OMZ across the last glacial cycle. Our results indicate persistently stronger deoxygenation in the northern Arabian Sea throughout the last glacial cycle. The OMZ expanded southward during the Last Glacial Maximum—likely driven by reduced ventilation and increased productivity from enhanced winter mixing of nutrients. During deglaciation, it retreated northward as southern-sourced intermediate waters intruded and productivity declined. We suggest that changes in ventilation and productivity, rather than water temperature, exerted the dominant control on Arabian Sea OMZ variability.

Spatially synchronized extreme precipitation events are intensifying under anthropogenic warming. Accurate simulation of such compound extremes by global climate models underpins reliable climate projections for spatially compound risk assessment. Using complex network analysis combined with event synchronization, here we evaluate the performance of 11 Coupled Model Intercomparison Project Phase 6 (CMIP6) models in representing global synchronized structures of extreme precipitation during 1981–2014. Compared to state-of-the-art reanalysis data, CMIP6 models effectively capture the scale-dependent behavior of synchronized event pairs, particularly for teleconnections beyond 2,500 km. While the CMIP6 multi-model ensemble mean overestimates short-range (300–2,500 km) synchronization frequency by 5.7%, it well reproduces the overall network topology of global extreme precipitation. However, significant regional biases emerge in monsoon regions, where models systematically underestimate node connectivity by more than 20% during boreal summer, highlighting key areas for model improvement in simulating long-distance synchronized precipitation events.

Tropical cyclones (TCs) can be considered as Carnot heat engines, where thermodynamic efficiency depends on the sea surface temperature (SST) and TC outflow temperature (T_o) in the upper atmosphere. This study investigates how TC efficiency in the western North Pacific (WNP) Ocean varies under different El Niño-Southern Oscillation (ENSO) conditions: the Eastern Pacific (EP), the Central Pacific (CP), and the Mixed El Niño types, as well as La Niña. We also explore how these changes affect a TC's theoretical upper bound (potential intensity (PI)). Using a reanalysis data set from 1979 to 2024, we find that TC efficiency decreases during La Niña, due to warmer T_o, and increases during CP El Niño, where upper-level cooling dominates. EP and Mixed El Niño show more heterogeneous responses. These efficiency changes contribute to PI variability from −38 to +27%, depending on ENSO type and region.

Internal modes of climate variability, such as El Niño and the North Atlantic Oscillation (NAO), can have strong influences upon distant weather patterns, effects that are referred to as “teleconnections.” The extent to which anthropogenic climate change has and will continue to affect these teleconnections, however, remains uncertain. Here, we employ a covariance fingerprinting approach to demonstrate that shifts in teleconnection patterns affecting monthly temperatures between the periods 1960–1990 and 1990–2020 are attributable to anthropogenic forcing. We further apply multilinear regression to assess the regional contributions and statistical significance of changes in five key climate modes: the El Niño-Southern Oscillation, NAO, Southern Annular Mode, Indian Ocean Dipole, and the Pacific Decadal Oscillation. In many regions, observed changes exceed what would be expected from natural variability alone, further implicating an anthropogenic influence. Finally, we provide projections of how these teleconnections will alter in response to further changes in climate.

Changes in tropical cyclone (TC) movement are commonly attributed to those in the steering flow, beta effect, or topographic influences. However, a series of idealized simulations suggest that significant track deflections can still occur even under a steady steering flow on an f plane. TCs embedded in easterly flows of varying strength systematically deflect southward from the expected westward track when radiative effects are included. The resulting track deflection reaches approximately 200 km in some experiments over a 144-hr period, comparable to typical 72- to 96-hr forecast errors in global numerical weather prediction model. A potential vorticity tendency analysis reveals that the deflection primarily results from the diabatic heating and horizontal advection terms, each linked to asymmetries in the convection and wind fields, respectively. These asymmetries are initially triggered by vortex–flow interactions and further enhanced by radiative diurnal cycles. Our findings highlight the role of internal vortex asymmetries in modulating TC motion.