Abstract

Surface melting occurs across many of Antarctica’s ice shelves, mainly during the austral summer. The onset, duration, area and fate of surface melting varies spatially and temporally, and the resultant surface meltwater is stored as ponded water (lakes) or as slush (saturated firn or snow), with implications for ice-shelf hydrofracture, firn air content reduction, surface energy balance and thermal evolution. This study applies a machine-learning method to the entire Landsat 8 image catalogue to derive monthly records of slush and ponded water area across 57 ice shelves between 2013 and 2021. We find that slush and ponded water occupy roughly equal areas of Antarctica’s ice shelves in January, with inter-regional variations in partitioning. This suggests that studies that neglect slush may substantially underestimate the area of ice shelves covered by surface meltwater. Furthermore, we found that adjusting the surface albedo in a regional climate model to account for the lower albedo of surface meltwater resulted in 2.8 times greater snowmelt across five representative ice shelves. This extra melt is currently unaccounted for in regional climate models, which may lead to underestimates in projections of ice-sheet melting and ice-shelf stability.

Understandably, material concerns dominate the policy conversation around sustainability and systemic transformation. Yet at the root level, our crises are created and perpetuated by factors in our psychology and meaning—making. 

From consumerist values to evolutionary impulses that skew our perceptions and political behaviours, these inner dynamics subtly dictate the course of our external world. It’s why Donella Meadows, the lead author of The Limits to Growth, saw this arena of “mindsets” as the “deepest leverage point for change.”

Abstract

Constraining the relationship between temperature and atmospheric concentrations of carbon dioxide (pCO2) is essential to model near-future climate. Here, we reconstruct pCO2 values over the past 15 million years (Myr), providing a series of analogues for possible near-future temperatures and pCO2, from a single continuous site (DSDP Site 467, California coast). We reconstruct pCO2 values using sterane and phytane, compounds that many phytoplankton produce and then become fossilised in sediment. From 15.0-0.3 Myr ago, our reconstructed pCO2 values steadily decline from 650 ± 150 to 280 ± 75 ppmv, mirroring global temperature decline. Using our new range of pCO2 values, we calculate average Earth system sensitivity and equilibrium climate sensitivity, resulting in 13.9 °C and 7.2 °C per doubling of pCO2, respectively. These values are significantly higher than IPCC global warming estimations, consistent or higher than some recent state-of-the-art climate models, and consistent with other proxy-based estimates.

cross-posted from: https://lemmy.world/post/16776366

Reuters.com

cross-posted from: https://lemmy.world/post/16748184

Axios.com

cross-posted from: https://lemmy.world/post/16748041

"As long as humans fill the atmosphere with fossil-fuel emissions, the heat will only get worse—vulnerable people will continue to die," an author of the analysis said.