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Surface and subsurface moored buoy, ship-based, remotely sensed, and reanalysis datasets are used to investigate thermal variability of northern Gulf of Alaska (NGA) nearshore, coastal, and offshore waters over synoptic to century-long time scales. NGA sea surface temperature (SST) showed a larger positive trend of 0.22 ± 0.10 °C per decade over 1970–2021 compared to 0.10 ± 0.03 °C per decade over 1900–2021. Over synoptic time scales, SST covariance between two stations is small (<10%) when separation exceeds 100 km, while stations separated by 500 km retain 50% of their co-variability for seasonal and longer fluctuations. Relative to in situ sensor data, remotely sensed SST data has limited accuracy in some NGA settings, capturing 60–70% of the daily SST anomaly in coastal and offshore waters, but often <25% nearshore. North Pacific and NGA leading modes of SST variability leave 25–50% of monthly variance unresolved. Analysis of the 2014–2016 Pacific marine heatwave shows that NGA coastal surface temperatures warmed contemporaneously with offshore waters through 2013, but deep inner shelf waters (200–250 m) exhibited delayed warming. Offshore surface waters cooled from 2014 to 2016, while shelf waters continued to warm from the combined effects of local air-sea and advective heat fluxes. We find that annually averaged Sitka air temperature is a leading predictor (r2 = 0.37, p < 0.05) for following-year NGA coastal water column temperature. Our results can inform future environmental monitoring designs, assist forward-looking projections of marine conditions, and show the importance of in situ measurements for nearshore studies that require knowledge of thermal conditions over time scales of days and weeks. 

Abstract. Although Arctic marine ecosystems are changing rapidly,year-round monitoring is currently very limited and presents multiplechallenges unique to this region. The Chukchi Ecosystem Observatory (CEO)described here uses new sensor technologies to meet needs for continuous,high-resolution, and year-round observations across all levels of theecosystem in the biologically productive and seasonally ice-covered ChukchiSea off the northwest coast of Alaska. This mooring array records a broadsuite of variables that facilitate observations, yielding betterunderstanding of physical, chemical, and biological couplings, phenologies,and the overall state of this Arctic shelf marine ecosystem. While coldtemperatures and 8 months of sea ice cover present challenging conditions forthe operation of the CEO, this extreme environment also serves as a rigoroustest bed for innovative ecosystem monitoring strategies. Here, we presentdata from the 2015–2016 CEO deployments that provide new perspectives on theseasonal evolution of sea ice, water column structure, and physicalproperties, annual cycles in nitrate, dissolved oxygen, phytoplankton blooms,and export, zooplankton abundance and vertical migration, the occurrence ofArctic cod, and vocalizations of marine mammals such as bearded seals. Theseintegrated ecosystem observations are being combined with ship-basedobservations and modeling to produce a time series that documents biologicalcommunity responses to changing seasonal sea ice and water temperatures whileestablishing a scientific basis for ecosystem management. 

Abstract From late‐summer 2013 to late‐summer 2014, a total of 20 moorings were maintained on the eastern Chukchi Sea shelf as part of five independent field programs. This provided the opportunity to analyze an extensive set of timeseries to obtain a broad view of the mean and seasonally varying hydrography and circulation over the course of the year. Year‐long mean bottom temperatures reflected the presence of the strong coastal circulation pathway, while mean bottom salinities were influenced by polynya/lead activity along the coast. The timing of the warm water appearance in spring/summer is linked to advection along the various flow pathways. The timing of the cold water appearance in fall/winter was not reflective of advection nor related to the time of freeze‐up. Near the latitude of Barrow Canyon, the cold water was accompanied by freshening. A one‐dimensional mixed‐layer model demonstrates that wind mixing, due to synoptic storms, overturns the water column resulting in the appearance of the cold water. The loitering pack ice in the region, together with warm southerly winds, melted ice and provided an intermittent source of fresh water that was mixed to depth according to the model. Farther north, the ambient stratification prohibits wind‐driven overturning, hence the cold water arrives from the south. The circulation during the warm and cold months of the year is different in both strength and pattern. Our study highlights the multitude of factors involved in setting the seasonal cycle of hydrography and circulation on the Chukchi shelf.