Observed Ocean Bottom Temperature Variability at Four Sites in the Northwestern Argentine Basin: Evidence of Decadal Deep/Abyssal Warming Amidst Hourly to Interannual Variability During 2009-2019

Consecutive multiyear records of hourly ocean bottom temperature measurements are merged to produce new decade-long time series at four depths ranging from 1,360 to 4,757 m within the northwest Argentine Basin at 34.5 degrees S. Energetic temperature variations are found at a wide range of time scales. All sites exhibit fairly linear warming trends of approximately 0.02-0.04 degrees C per decade over the period 2009-2019, although the trends are only statistically different from zero at the two deepest sites at depths of similar to 4,500-4,800 m. Near-bottom temperatures from independent conductivity-temperature-depth profiles collected at these same locations every 6-24 months over the same decade show roughly consistent trends. Based on the distribution of spectral energies at the deepest sites and a Monte Carlo-style analysis, sampling at least once per year is necessary to capture the significant warming trends over this decade to within 50% error bars at a 95% confidence limit.