GRACE-Based Assessment of Interannual Snow Water Equivalent Variability and Climate Teleconnections over the Northern Hemisphere.

Snow Water Equivalent (SWE) is a critical component of the terrestrial water cycle, yet its large-scale variability and sensitivity to climate teleconnections remain poorly constrained due to sparse in situ observations and uncertainties in land surface models. Using monthly GRACE and GRACE-FO observations from 2003–2024, this study investigates the interannual variability of Northern Hemisphere SWE and its relationship with major climate oscillations, including the El Niño–Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), and the Pacific Decadal Oscillation (PDO). GRACE-derived terrestrial water storage anomalies are disaggregated to estimate SWE variability using a mass-conserving, GRACE-constrained framework over regions north of 34.5°N, corresponding to approximately 65% of the global seasonal snow-covered land area. Empirical Orthogonal Function (EOF) analysis of detrended and deseasonalized SWE anomalies reveals that the first three modes explain approximately 45–60% of total interannual SWE variance. ENSO is significantly correlated with the second and third SWE modes (r = 0.4–0.6, p < 0.05), which together account for 10–25% of regional SWE variance in western North America and parts of Central Asia. ENSO-related SWE anomalies exhibit a clear dipole structure and a lagged response of 1–4 months, with stronger sensitivity during the melt season than the accumulation season. In contrast, NAO-driven modes dominate SWE variability across northern Europe, explaining up to 30% of regional variance. These results demonstrate that large-scale climate teleconnections modulate SWE primarily through persistent precipitation anomalies rather than temperature alone, while ENSO explains a limited but quantifiable fraction of hemispheric-scale snow mass variability.

Keywords: GRACE, Snow water equivalent, ENSO, Climate change, precipitation, snow.