Award: OCE-1756105

The Bermuda Atlantic Time-series Study (BATS) research program has nearly completed its 36th year. This report includes activities that have taken place since the inception of the award initiated in August 2018 to the present time. The BATS project was established in the late 1980s by NSF to support monitoring of and experimental work on the physics, chemistry, and biology of the ocean, at a location approximately 85 km to the southeast of the island of Bermuda in the North Atlantic Ocean. Since then, the BATS site has been sampled monthly to bimonthly during more than 480 cruises to date, with laboratories, research and logistical support, and ship support (R/V Atlantic Explorer) based at the Bermuda Institute of Ocean Sciences (BIOS). Oceanographic data collected provide critical information about ocean changes taking place and what these changes might mean to the future of our oceans. From the late 1980s, surface and upper ocean subtropical waters of the North Atlantic Ocean have grown warmer (+1.2C) and saltier (+0.11), lost oxygen (~8% over past 40 years) but gained anthropogenic carbon dioxide (CO2; 72% increase). Ocean biology and community structure has also changed, with primary production decreasing while organic carbon export has been maintained (Lomas et al., 2022; Ivory et al., 2019). In the recent decade, physical and biogeochemical changes in the upper ocean have accelerated (Bates and Johnson, 2020, 2022, 2023). For the award period, we have completed 60 core BATS cruises, 10 bloom cruises, and 5 validation cruises. The number of core BATS cruises is 418 since October 1988, with an additional 97 bloom cruises and 60 validation type cruises, for a combined total of 595 BATS cruises. For the past decade, CTD profiling was extended to full ocean depth while previously, the maximum depth was 4,200 m. This has resulted in an extra sample at the near bottom depth (~4,550 m) that requires an additional cast to get all the 37 BATS core discrete depths. Other than the occasional Niskin misfire, a 100% success rate was achieved for most CTD casts with a total of nearly 20,000 bottle samples. To date, the BATS program has conducted approximately ~16,000 CTD casts over the past 35 years in the Sargasso Sea. In addition to the BATS core and bloom cruises, there was fivesuccessful validation cruise conducted during this period.A validation cruise, BVAL60, comprised a return transect section between Puerto Rico to 35N. Long-term ocean time series are a powerful tool for investigating ocean physics and biogeochemistry, effects on the global carbon cycle, and responses to ocean change. The original and continuing theme of the BATS program has been, and continues to be, improving our understanding of the time-varying components of the ocean carbon cycle, related biogenic elements of interest (e.g., nitrogen, phosphorus, silica), and identifying the relevant physical, chemical and ecosystem properties responsible for this variability. Critical evaluation of seasonal, interannual and longer-scale dynamics of vertical mixing, control of ecosystem productivity by carbon and nutrient cycles, net exchange of CO2 between the atmosphere and the ocean, and distribution of many biogenic elements within the sea requires longterm sustained observations. Over the past 70 years, an upper-ocean (~0-450 m) warming trend first recognized in the 1970s has strengthened in recent decades (about 1.2 C since the 1970s; increase in upper ocean heat content of ~1.2 W m-2). A contemporaneous increase in salinity of ~0.2 was observed over this period (Bates and Johnson, 2020, 2022). The warming and salinification over the last decade have been ~0.8C and 0.1, respectively, with rapid changes in the last five years. As of July 2024, approximately 700 peer-reviewed papers with BATS data have been published since the inception of the project in 1988 (see Broader Impacts section), with publication of ~25 papers on average each years (https://scholar.google.com/citations?hl=en&user=l1Qh9LgAAAAJ&view_op=list_works&sortby=pubdate). Papers with BATS data have been cited in the literature over 125,000 times (4,500-6,000 per year), and with an h-index of 165 and i-10 value of 613, respectively. BATS data are primarily archived at the Biological and Chemical Oceanography Data Management Office (BCO-DMO) BCO-DMO is the primary host and distributor of BATS data (https://www.bco-dmo.org/project/2124) with a planned six-month release data of new data and Digital Object Identifiers (DOIs). The data access and dois available through BCO-DMO include ten datastreams. Last Modified: 11/27/2024 Submitted by: NicholasRBates