Geophysical Research Letters最新文献

The seasonal delay of tropical rainfall is a robust feature under global warming. This study finds that the seasonal delay of tropical rainfall is much more pronounced under spatially patterned sea surface temperature (SST) warming compared to uniform SST warming. Through the lens of the atmospheric energetic framework, we show that the enhanced seasonal delay is primarily driven by the interhemispheric contrast in SST warming between the Northern and Southern Hemispheres, which intensifies the inter-seasonal difference in cross-equatorial atmospheric energy transport between transition seasons. The SST warming features are found to be crucial, characterized by both its seasonal cycle and annual mean. The former is closely related to the seasonal delay of SST, especially in the northern high latitude, while the latter is further demonstrated by an atmospheric model forced with the annual-mean spatially patterned SST warming.

The future tropical sea surface temperature (SST) changes profoundly impact global and regional climate. Under greenhouse warming, the reduction of Antarctic sea ice concentration (SIC) acts as an extratropical energy perturbation, exerting a substantial influence on the spatial distribution of tropical SST change. This study reveals a strong correlation between the current Antarctic SIC and tropical SST change, especially the interhemispheric asymmetry and El Niño-like pattern under greenhouse warming among CMIP6 models. Considering the commonly underestimated Antarctic SIC in CMIP6 models, this study applies an emergent constraint on the projected tropical SST response to greenhouse warming using the observed Antarctic SIC. The interhemispheric asymmetry in projected tropical SST warming can be markedly diminished in the multi-model ensemble mean, with a 30% reduction in the intermodel uncertainty. The spatial constraints on the projected tropical Pacific SST change produce a more pronounced and westward-extended El Niño-like warming pattern.

The Bølling-Allerød deglacial event is marked by high diatom productivity and opal deposition throughout the subarctic Pacific. This opal could either constitute a strengthened biological pump and thus carbon sequestration, or a weakened biological pump and release of marine-sequestered CO₂ to the atmosphere. We quantify silicic acid supply at IODP Site U1340 in the Bering Sea using biogenic opal and δ³⁰Si of Coscinodiscus, a diatom genus. These records, along with diatom environmental indicators, suggest the Bølling-Allerød had high silicic acid availability related to a shift from stratification to seasonal upwelling dynamics. We thus propose the primary cause of the high productivity event was increased macronutrient supply from vertical exchange that injected old, nutrient-rich, CO₂-rich waters into the surface. Enhanced CO₂ release from the subarctic Pacific may help explain critical intervals of CO₂ rise that occur at the onsets of the Bølling-Allerød and PreBoreal.

On early Mars, the integration of surface, groundwater, and climate systems into an integrated hydrological system remains poorly understood. The partitioning of precipitation, between surface and groundwater via infiltration, controls the Martian aquifer recharge rates and, subsequently, surface erosion processes. We investigate infiltration at two scales, near-surface and deep crustal. We estimate infiltration timescales, revealing that near-surface water loss enhances aeolian erosion over short periods (hours to days). Deep crustal recharge, which requires decades to centuries, affects the deep aquifer response and the water budget. Martian crustal heterogeneity influences infiltration dynamics and runoff production making them dependent on the duration of precipitation. This interaction suggests that the responses of the aquifers to recharge events and groundwater upwelling likely lag behind climate optimum conditions. The accommodation space between topography and aquifer influences Mars' water budget by transiently sequestering water, thus limiting the available water for surface evaporation and inclusion in climate dynamics.

Precise point positioning (PPP) of ships using Global Navigation Satellite System (GNSS) data reveals the precise movements of marine vessels. This method may quantify anomalies in sea surface height with implications for oceanographic monitoring, exploration, and tsunami warning. The GNSS PPP data from the R/V Sikuliaq, a research ship of the University of Alaska Fairbanks, were processed to detect a small local tsunami generated by the Lowell Point landslide, which occurred near Seward, Alaska, on 8 May 2022 (UTC). The GNSS receiver aboard the R/V Sikuliaq recorded the waves generated by the landslide, with a maximum wave amplitude of 6 cm and wave periods between 40 and 50 s. These results are consistent with simulations of the landslide event.

Future changes in the Beaufort Gyre liquid freshwater content (LFWC) are important for the local and global climate. However, traditional climate models cannot resolve oceanic and atmospheric eddies that are critical to the LFWC variations. In this study, we investigate physical processes controlling Beaufort Gyre LFWC changes in an eddy-resolving simulation. The model simulation largely reproduces the observed LFWC changes, and projects a long-term LFWC increase with an intensification of its decadal variability during the 21st century. Freshwater budget analysis suggests that future LFWC changes are strongly influenced by sea ice melt. The conversion from solid to liquid phase provides more liquid freshwater into the ocean. Meanwhile, sea ice loss enhances the efficiency of air-sea momentum transfer, leading to increased wind-driven freshwater convergence and its variability. The decadal variation of the LFWC will regulate Arctic freshwater exports and coincident with an O (0.5 Sv) change in the meridional overturning circulation.

Sterodynamic sea level (SdynSL) is an essential component of sea level that climate models can simulate directly. Here, we disentangle the impacts of intermodel uncertainty, internal variability, and scenario uncertainty on SdynSL projections from Coupled Model Intercomparison Project Phase 6 (CMIP6) models. Regarding the global mean, intermodel (scenario) uncertainty dominates before (after) ∼2070, while internal variability is negligible. At the regional scale, intermodel uncertainty is the largest contributor, whereas internal variability plays a secondary role mainly in the tropical Indo-Pacific Ocean. Scenario uncertainty becomes significant in certain regions toward the end of this century. The anthropogenic signal of global mean SdynSL emerges at the beginning of this century relative to 1971–2000. In contrast, the anthropogenic signals of regional SdynSL are likely to emerge over 70% of the global ocean by the 2090s, which could be advanced to the 2040s if model differences can be totally eliminated.

Rock dissolution is a common subsurface geochemical reaction affecting pore space properties, crucial for reservoir stimulation, carbon storage, and geothermal energy. Predictive models for dissolution remain limited due to incomplete understanding of the mechanisms involved. We examine the influence of flow, transport, and reaction regimes on mineral dissolution using 29 time-resolved data from 3D rocks. We find that initial pore structure significantly influences the dissolution pattern, with reaction rates up to two orders of magnitude lower than batch conditions, given solute and fluid-solid boundary constraints. Flow unevenness determines the location and rate of dissolution. We propose two models describing expected dissolution patterns and effective reaction rates based on dimensionless metrics for flow, transport, and reaction. Finally, we analyze feedback between evolving flow and pore structure to understand conditions that regulate/reinforce dissolution hotspots. Our findings underscore the major impact of flow arrangement on reaction-front propagation and provide a foundation for controlling dissolution hotspots.

Wet-bulb temperature extremes (WTEs) occur due to a combination of high humidity and temperature, and are hazardous to human health. Alongside favourable large-scale conditions, surface fluxes play an important role in WTEs; yet, little is known about how land surface heterogeneity influences them. Using a 10-year, pan-African convection-permitting model simulation, we find that most WTEs have spatial extents 2,000 $��{\text{km}}^2�$. They occur preferentially over positive soil moisture anomalies (SMA) typically following rainfall. The wet-bulb temperature is locally amplified by 0.5–0.6$��°�$C in events associated with smaller-scale SMA (50 km across) compared to events with larger-scale SMA (300 km across). A mesoscale cifrculation, resulting from stronger spatial contrasts of sensible heat flux, more efficiently concentrates moist, warm air in a shallower boundary layer. This mechanism could explain the underestimation of peak Twb values in coarser-resolution products. The role of antecedent SMA from recent rainfall may help issue localized early warnings.

A regime shift is an abrupt, substantial, and persistent change in the state of a system. We show that a regime shift in the September Arctic sea-ice extent (SIE) occurred in 2007. Before 2007, September SIE was declining approximately linearly. In September 2007, SIE had its largest year-to-year drop in the entire 46-year satellite record (1979–2024). Since 2007, September SIE has fluctuated but exhibits no long-term trend. The regime shift in 2007 was caused by significant export and melt of older and thicker sea ice over the previous 2–3 years, as documented in other studies. We test alternatives to the traditional linear model of declining September SIE, and discuss possible explanations for the lack of a trend since 2007.