Urban ponds, whether connected to or isolated from channelized drainage networks, provide ecosystem services to the landscape. The relative physical and chemical conditions between the two types have rarely been studied in non-growing season months. This study examines the stark differences in temperature, salinity, dissolved oxygen, and phosphate patterns between adjacent open and closed ponds over contrasting wintertime conditions. The persistent presence of ice cover in the open pond during cold winters resulted in winter-long anoxia and elevated phosphate levels throughout the water column. In contrast, during cold winters the closed pond remained aerated (> 10 mg DO/L) with low dissolved reactive phosphate concentrations (<0.05 mg/L) for the first half of the ice-over period. During mild winters, with sporadic or negligible ice cover, dissolved oxygen was high and phosphate low in the near-surface waters of the open pond, but deeper waters were anoxic (DO < 2.0 mg/L) with elevated dissolved phosphate (up to 0.3 mg/L). The deepwater oxygen depletion did not occur in the closed pond during minimal ice-over, mild winters, reflecting a well-mixed water column. These differences between pond type (open/closed) and winter temperature (ice/no-ice) reflect the interplay between photosynthetic activity (increased DO) and differential road salt input, which in the open pond led to chemically induced water column stratification. Results of this study demonstrate that winter phenology and hydrogeomorphology are important controls on urban pond ecosystem dynamics and need to be considered in process and conceptual models of urban water courses.