Are the Sermilik Fjord glaciers terminus-controlled, runoff-controlled, or runoff-adapting? Decomposition of glacier speed maps at Helheim, Fenris, Midgard, and Pourquoi-Pas Glaciers Previous research has identified three common seasonal patterns (“types”) of ice flow at Greenland glaciers (Moon et al., 2014; Vijay et al., 2019). Some glaciers have a consistent type, while others change from year to year. Neighboring glaciers may have the same or different type. Previously, types were identified by examining flow at a single point. This limitation may affect the inferred variability. We use principal component (PC) / empirical orthogonal function (EOF) analysis to decompose maps of ice speed (Joughin et al., 2018; Joughin, 2021; Howat, 2020; Scambos et al., 206; Rosenau et al., 2015; Solgaard & Kusk, 2021) at four glaciers feeding Sermilik Fjord over 2014-2021. This improves on the previous single-point method by yielding temporal patterns (PCs), which allow types to be identified, plus their associated spatial patterns (EOFs). Helheim Glacier shows the most spatial and temporal heterogeneity of the four glaciers. PC #1 (95% of the variance in 2014-2021 speed) suggests primarily terminus control (p=0.003) but also some runoff control (p=0.05). PC #2 (1% of the variance in 2014-2021 speed) shows only runoff control (p=0.006). Previous work found that Helheim can be either terminus- or runoff-controlled. Fenris Glacier is runoff-adapting (PC #1, 66% of the variance in 2014-2021 speed). This disagrees with previous work that classified it as terminus-controlled. On Midgard Glacier, PC #1 (79% of the variance in 2014-2021 speed) is consistent with runoff-adapting behavior (p<0.0001). EOF #2 shows that the lowest 4 km is more runoff-controlled (p<0.00001) or terminus-controlled (p=0.04) than the upstream area. Our conclusion agrees with previous work that classified Midgard as runoff-adapting. Since separating from Midgard in 2009, Pourquoi Pas Glacier has slowed near the terminus while accelerating upstream. EOF #1 shows this pattern (67% of the variance in 2014-2021 speed); its PC shows runoff control. Previous work classified Pourquoi Pas as terminus-controlled. Overall, these results agree moderately with previous, simpler analyses. Thus, application of EOF/PC analysis to the popular “glacier type” problem holds some promise in the quest to discover what controls the seasonal flow patterns of Greenland glaciers.