Springtime warming over Northern Mid-High-latitude Land profoundly affects plant life cycles and water resources, yet large model uncertainty limits climate risk assessment. Here, we develop a novel emergent constraint that targets the key uncertainty source—model divergence in surface-albedo feedback linked to historical snowmelt sensitivity. This approach halves the spread of projected warming and reveals a pronounced geographical asymmetry. Under the high-emission scenario (SSP5-8.5), current climate models underestimate end-of-century warming over Eurasia by 0.80°C but overestimate it over North America by 0.44°C. These refined projections substantially alter ecological outcomes: the start of the growing season is predicted to advance by about 18 days in Eurasia and 8 days in North America, representing a 3-day greater advance and 1-day delay compared with original estimates. Our findings offer a more reliable basis for assessing climate change impacts on ecosystems and water resources and highlight the urgency of region-specific adaptation strategies.
Snow dampens sounds, but anecdotal reports concisely describe audible propagating collapse events—firnquakes—in Antarctic and Arctic snowfields. We propose combining granular and continuum mechanics to form a testable theory for conditioning, triggering, and propagation of firnquakes consistent with scarce data. A central condition for collapse events is unconsolidated firn at depth. As firn grains compact, stresses are transmitted along force chains which carry the overburden and transition into a continuous medium by pressure sintering. This granular legacy creates solid-like supports of denser layers that keep the material below unconsolidated. Dynamic amplification triggers local brittle failure of the supports, which induces a cascade of collapse propagation. Using bulk density from ice cores as proxy for stiffness, we find the flexural wave speed by collapsing supports matches the recorded firnquake velocities on the order of 100 m/s. Our theory is to be tested in firn sheets and other compacting granular materials.
Kinetic energy (KE) transfer between spatial scales contributes to the ocean's energy budget by linking scales of KE supply and KE dissipation. Numerical simulations have indicated that for scales smaller than the baroclinic deformation radius, cross-scale KE transfer has complex spatial and temporal variability, modulated by mixed layer properties, fronts, and eddies. Here, over a decade of upper-ocean surface velocity data, collected from high-frequency radar within the Santa Barbara Channel, are used to estimate cross-scale KE transfer. The transfer of KE across 7 km has strong seasonal and interannual variations linked to energy exchange with the atmosphere. This study observationally confirms (a) the importance of the surface divergence field in determining the direction of the KE transfer and (b) the equi-partitioning of KE transfer between divergent and straining motions. The temporal variability in KE transfer suggests that surface forcing influences the long-term redistribution of energy between scales.
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