Wind‐Modulated Western Maine Coastal Current and Its Connectivity With the Eastern Maine Coastal Current

• Published in: Journal of geophysical research. Oceans 2022-06, Vol.127 (6), p.n/a
• Main Authors: Li, Denghui, Wang, Zhengui, Xue, Huijie, Thomas, Andrew C., Etter, Ron J.
• Format: Article
• Language: English
• Subjects: Coastal currents; Coasts; Connectivity; Counterflow; Domes; Geophysics; Modelling; Offshore; Particle tracking; Resolution; River discharge; River flow; River runoff; Rivers; Runoff; Sea level; Spring; Spring (season); Summer; Variation; Water surface slope; Wind; Winter
• ISSN: 2169-9275; 2169-9291
• DOI: 10.1029/2022JC018469

Using a high‐resolution circulation model and an offline particle tracking model, we investigated variations of the Western Maine Coastal Current (WMCC) and its connectivity with the Eastern Maine Coastal Current (EMCC). The models showed that the weak, broad, and sinuous WMCC is generally southwestward with an offshore and a nearshore core, fed by the extension of the EMCC and runoff from the Penobscot and Kennebec–Androscoggin Rivers, respectively. A sea‐level dome can form offshore of Casco Bay in late fall and early winter as the northeastward alongshore wind sets up a seaward sea‐level gradient from the coast to meet the shoreward sea‐level gradient from Wilkinson Basin. Consequently, northeastward flows (i.e., the counter‐WMCC) emerge on the inshore side of the dome. Both the circulation and particle tracking models suggested that the connectivity generally peaks twice annually, highest in winter and then secondarily in late spring or early summer. The former is concurrent with the most southwest offshore veering of the EMCC, while the latter is concurrent with the strongest EMCC. Moreover, the counter‐WMCC can reduce the connectivity and result in year‐to‐year variations. Plain Language Summary Using a high‐resolution circulation model and offline particle tracking model, we investigated the variations of coastal current in the western Gulf of Maine (GoME) and its connectivity with flows in the eastern GoME. Our models showed that the coastal flows in the western GoME generally exist as an offshore and nearshore core, stemming from the extension of flows in the eastern GoME and local river runoff, respectively. In late fall and early winter, the offshore transport driven by northeastward alongshore wind converges with the raised sea level around Wilkinson Basin, forming a sea‐level dome. On the inshore side of the dome, the sea level slopes down toward the coast, which results in northeastward (counter) flows. Connectivity between the western and eastern GoME coastal flows generally peaks in winter and again in late spring or early summer, due to the variations of the strength and offshore veering of the Eastern Maine Coastal Current. The counter flows can reduce the connectivity and add to the year‐to‐year variations. Key Points Western Maine Coastal Current has two cores, fed by river runoff and the Eastern Maine Coastal Current, respectively Strong northeastward alongshore wind can reverse the Western Maine Coastal Current in late fall and early