Subglacial hydrology can exert an important control on ice flow by affecting drag at the ice-bedrock interface. Here, we report on a series of subglacial drainage events (outbursts) along the Northeast Greenland Ice Stream (NEGIS), initiating as far inland as ~500 km from the margin of Zachariae Isstrøm. The drainage events are associated with local transient uplift, followed by prolonged subsidence, measured by satellite synthetic aperture radar interferometry (DInSAR). In downstream regions, drainage events are associated with a local speed-up in ice flow. The high spatiotemporal resolution of the DInSAR measurements allows for a detailed mapping of the drainage propagation pathway. We show that multiple drainage cascades have occurred along the same identified pathway over the years 2020-2022. Finally, the propagation speed of subglacial water flow is found to vary greatly along NEGIS, suggesting that fundamental differences may exist in the subglacial environment.

Earth is warming and sea levels are rising as land-based ice is lost to melt, and oceans expand due to accumulation of heat. The pace of ice loss and steric expansion is linked to the intensity of warming. How much faster sea level will rise as climate warms is, however, highly uncertain and difficult to model. Here, we quantify the transient sea level sensitivity (TSLS) of the sea level budget in both models and observations. Models show little change in sensitivity between the first and second half of the 21st century for most contributors. The exception is glaciers and ice caps (GIC) that have a greater sensitivity pre-2050 (2.8±0.4 mm/yr/K) compared to later (0.7±0.1 mm/yr/K). We attribute this change to the short response time of glaciers and their changing area over time. Model sensitivities of steric expansion (1.5±0.2 mm/yr/K), and Greenland Ice Sheet mass loss (0.8±0.2 mm/yr/K) are greater than, but still compatible with, corresponding estimates from historical data (1.4±0.5 mm/yr/K and 0.5±0.1 mm/yr/K). Antarctic Ice Sheet (AIS) models tends to show lower rates of sea level rise with warming (‑0.0±0.3 mm/yr/K) in contrast to historical estimates (0.4±0.2 mm/yr/K). This apparent low bias in AIS sensitivity is only partly able to account for a similar low bias identified in the sensitivity of GMSL excluding GIC (3.2±0.5 mm/yr/K vs 2.2±0.4 mm/yr/K). The balance temperature, where sea level rise is zero, lies close to the pre-industrial value, implying that sea level rise can only be mitigated by substantial global cooling.