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"The Central Arctic Ocean remains profoundly understudied, particularly with respect to carbon cycling, ecosystem alteration, and associated changes in atmospheric, ice and ocean physics that drive those biological and biogeochemical systems. The region is expected to experience continued marked changes over the coming decades, driven by ongoing climate warming. Yet, because of relatively limited understanding of fundamental characteristics and processes in the region, predicting these changes and their Pan-Arctic linkages remains difficult. The Synoptic Arctic Survey (SAS) is organized around three major research areas: (1) physical drivers of importance to the ecosystem and carbon cycle; (2) the ecosystem response and (3) the carbon cycle. The overarching questions are: “What is the present state, and what are the major ongoing transformations of the Arctic marine system?” The overall objective of this expedition was to quantify the present states of the physical, biological, and biogeochemical systems of the Pacific Arctic (here defined as the Chukchi Sea, Beaufort shelf/slope, Chukchi Borderlands) and Canadian Basin (i.e., the Makarov and Canada basins) during summer 2022." - Cruise Report USCGC Healy HLY2202/AWS2022 [Prepared by Carin Ashjian (cashjian@whoi.edu) and the HLY2202 Science Team]. This dataset presents upper ocean (75 meters) chlorophyll-a and pheophytin concentrations collected at hydrographic stations. Pheophytin proportions are additionally provided to inform on the relative freshness of observed phytoplankton blooms. 

Decreased sea ice cover in the northern Bering Sea has altered annual phytoplankton phenology owing to an expansion of open water duration and its impact on ocean stratification. Limitations of satellite remote sensing such as the inability to detect bloom activity throughout the water column, under ice, and in cloudy conditions dictate the need for shipboard based measurements to provide more information on bloom dynamics. In this study, we adapted remote sensing land cover classification techniques to provide a new means to determine bloom stage from shipboard samples. Specifically, we used multiyear satellite time series of chlorophyll a to determine whether in-situ blooms were actively growing or mature (i.e., past-peak) at the time of field sampling. Field observations of chlorophyll a and pheophytin (degraded and oxidized chlorophyll products) were used to calculate pheophytin proportions, i.e., (Pheophytin/(Chlorophyll a + Pheophytin)) and empirically determine whether the bloom was growing or mature based on remotely sensed bloom stages. Data collected at 13 north Bering Sea stations each July from 2013–2019 supported a pheophytin proportion of 28% as the best empirical threshold to distinguish a growing vs. mature bloom stage. One outcome was that low vs. high sea ice years resulted in significantly different pheophytin proportions in July; in years with low winter-to-spring ice, more blooms with growing status were observed, compared to later stage, more mature blooms following springs with abundant seasonal sea ice. The detection of growing blooms in July following low ice years suggests that changes in the timing of the spring bloom triggers cascading effects on mid-summer production.