Arctic Ocean bathymetry and its connections to tectonics, oceanography and climate
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Active ice sheet conservation cannot stop the retreat of Sermeq Kujalleq glacier, Greenland
Active conservation of an ice sheet seeks to reduce ice sheet mass loss and sea level rise. Here we explore the response of Sermeq Kujalleq in Greenland to limiting warm water inflow to the fjord it terminates by raising the sill by an artificial barrier at its mouth. We asynchronously couple an ice sheet model with a fjord model, and simulate glacier evolution with varying climate scenarios from the year 2020 to 2100. The tallest barrier cools the fjord water and reduces melt at the ice front. But this has minor impacts on glacier retreat under SSP5-8.5 and SSP2-4.5. Cooling the atmospheric forcing to 1990s levels reduces glacier retreat, but even reducing water temperatures with a barrier cannot stabilize the glacier. The glacier seems to be in an unstoppable phase of marine ice sheet instability on a rapidly deepening retrograde sloping bed and in water much deeper than in 2000s.
Event triggers and opinion leaders shape climate change discourse on Weibo
Understanding how real-world events and opinion leaders shape climate change discussions is vital for improving communication and policy formulation to meet global carbon mitigation goals. This study analyzed 5.3 million original posts from Weibo (2012–2022), China’s largest social media platform, to examine climate change discourse. We found five event types triggering 48 discussion peaks, including online activities, international conferences, extreme weather, domestic policies, and international news. Posts generally conveyed positive attitudes, though sentiment decreased during haze pollution and the COVID-19 pandemic. Network analysis revealed seven opinion leader groups with distinct strategies: official media and institutions emphasized political will, global initiatives, and socio-economic implications, while universities and grassroots individuals focused on scientific reality and personal actions. Celebrities and unofficial accounts often highlighted geopolitical topics, especially China-US relations. We suggest reducing fragmented echo chambers and fostering personal connections through digital media platforms to enhance public awareness.
Onshore intensification of subtropical western boundary currents in a warming climate
Subtropical western boundary currents (WBCs) refer to swift narrow oceanic currents that flow along the western edges of global subtropical ocean basins. Earlier studies indicated that the WBCs are extending poleward under a warming climate. However, owing to limited observations and coarse resolution of climate models, how greenhouse warming may affect the zonal structure of the WBCs remains unknown. Here, using seven high-resolution climate models, we find an onshore intensification of the WBCs in a warming climate. The multimodel ensemble mean of onshore acceleration ranges from 0.10 ± 0.08 to 0.51 ± 0.24 cm s−1 per decade over 1950–2050. Enhanced oceanic stratification associated with fast surface warming induces an uplift of the WBCs, leading to the projected change. The onshore intensification could induce anomalous warming that exacerbates coastal marine heatwaves, reduces ability of the coastal oceans to absorb anthropogenic carbon dioxide and destabilizes methane hydrate stored below the sea floor of shelf regions.
Climate change threatens crop diversity at low latitudes
Climate change alters the climatic suitability of croplands, likely shifting the spatial distribution and diversity of global food crop production. Analyses of future potential food crop diversity have been limited to a small number of crops. Here we project geographical shifts in the climatic niches of 30 major food crops under 1.5–4 °C global warming and assess their impact on current crop production and potential food crop diversity across global croplands. We found that in low-latitude regions, 10–31% of current production would shift outside the climatic niche even under 2 °C global warming, increasing to 20–48% under 3 °C warming. Concurrently, potential food crop diversity would decline on 52% (+2 °C) and 56% (+3 °C) of global cropland. However, potential diversity would increase in mid to high latitudes, offering opportunities for climate change adaptation. These results highlight substantial latitudinal differences in the adaptation potential and vulnerability of the global food system under global warming.
Mixed-layer lipidomes suggest offshore transport of energy-rich and essential lipids by cyclonic eddies
Mesoscale eddies are ubiquitous features in the ocean affecting the cycles of nutrients and carbon. Cyclonic eddies formed in Eastern Boundary Upwelling Systems can substantially modulate primary production by phytoplankton and the vertical and lateral export of organic carbon. However, the impact of eddy activity on the biochemical composition of eukaryotic phytoplankton, bacteria and archaea and associated consequences for carbon and energy flows are largely unknown. Here, we investigated the microbial lipidome in the surface ocean in and around a cyclonic eddy formed in the coastal upwelling system off Mauritania. We show that the eddy contained almost three times the amount of lipids compared to the surrounding open-ocean and coastal waters. The eddy lipid signature with energy-rich triacylglycerols and essential fatty acid-containing membrane lipids of eukaryotic phytoplankton origin was further significantly different from the ambient waters. Strong variability in lipid distributions within the eddy was related to differences in microbial community composition. Estimates indicate that in the Mauritanian upwelling area, as much as 9.7 ± 2.0 gigagrams of lipid carbon per year is delivered to the open ocean by coastal cyclonic eddies potentially fueling higher trophic levels and contributing to the maintenance of secondary productivity and carbon export offshore.
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