The atmospheric marine boundary layer (AMBL) plays a crucial role in regulating air-sea interactions and influencing the climate system, particularly in the Arctic due to its high sensitivity to global warming. This study utilizes five years (2018-2022) of saildrone data from the Bering-Chukchi-Beaufort Seas to analyze atmospheric near-surface stability and air-sea turbulent heat fluxes during the Arctic summer. By applying Monin-Obukhov similarity theory (MOST), we investigate the temporal variability and mechanisms that influence AMBL stability. Our findings reveal two distinct regimes of stable and unstable conditions in two contrasting years of 2020 and 2022. In 2020, cold air advection driven by northerly winds consistently destabilizes the AMBL, leading to increased oceanic heat loss. In 2022, however, southerly winds and warm air advection stabilize the AMBL, suppressing air-sea heat exchanges. The temporal variation of turbulent heat fluxes is primarily driven by air-sea temperature differences, with the magnitude of wind speed and its temperature covariance serving as secondary factors. We also show the importance of skin temperature measurements from saildrones for improving estimates of turbulent heat fluxes. These insights enhance our understanding of Arctic air-sea interactions and inform climate models, underscoring the need for high-resolution observations in polar regions and the improvement of bulk flux parameterization for stable AMBL.

Years of the Maritime Continent (YMC) is a multi-year international program with participants from over 15 countries. Its overarching goal is to expedite the progress of improving understanding and prediction of local oceanic and atmospheric multi-scale variability of the Indo-Pacific Maritime Continent (MC) and its global impact through observations and modeling exercises. YMC is motivated by unique role of the MC in the local and global weather-climate system, our lack of understanding of the key processes governing this role, and persistent systematic regional biases and errors in numerical models. YMC builds a comprehensive database of the MC weather-climate system and educates the next generation of scientists who will be the core workforce and leaders to further advance the study of the MC.

The western Arctic marginal seas undergo large seasonal variation, but are very challenging to observe directly due to sea ice and shallow depths. Deployments of several saildrone uncrewed surface vehicles (USVs) in the summers of 2018 and 2019 provided unique opportunities to validate the satellite-derived near surface currents, Ocean Surface Current Analysis Real-time (OSCAR), in the western Arctic marginal seas against in situ upper ocean current measurements. Overall, OSCAR current is biased low with significant noise. Higher vector correlation and speed difference often occur where stronger currents (often topography-steered) are observed. Such differences reveal that the dataset resolvability depends on spatial and temporal resolutions, smoothing, and latitudes, suggesting that OSCAR is able to depict the major current systems but significantly underestimates their strength. Poorer vector correlation occurs at weaker current regimes (< 10 cm/s), over the shallow Hanna Shoal, near fresher water due to ice melt and river discharge. The latter two water class regimes highlight the importance of salinity contribution to the buoyancy force which is neglected in the OSCAR formulation.

The science guiding the \EURECA campaign and its measurements are presented. \EURECA comprised roughly five weeks of measurements in the downstream winter trades of the North Atlantic — eastward and south-eastward of Barbados. Through its ability to characterize processes operating across a wide range of scales, \EURECA marked a turning point in our ability to observationally study factors influencing clouds in the trades, how they will respond to warming, and their link to other components of the earth system, such as upper-ocean processes or, or the life-cycle of particulate matter. This characterization was made possible by thousands (2500) of sondes distributed to measure circulations on meso (200 km) and larger (500 km) scales, roughly four hundred hours of flight time by four heavily instrumented research aircraft, four global-ocean class research vessels, an advanced ground-based cloud observatory, a flotilla of autonomous or tethered measurement devices operating in the upper ocean (nearly 10000 profiles), lower atmosphere (continuous profiling), and along the air-sea interface, a network of water stable isotopologue measurements, complemented by special programmes of satellite remote sensing and modeling with a new generation of weather/climate models. In addition to providing an outline of the novel measurements and their composition into a unified and coordinated campaign, the six distinct scientific facets that \EURECA explored — from Brazil Ring Current Eddies to turbulence induced clustering of cloud droplets and its influence on warm-rain formation — are presented along with an overview \EURECA’s outreach activities, environmental impact, and guidelines for scientific practice.