NOAA’s Western Boundary Time Series (WBTS) project, alongside partner projects RAPID and MOCHA, have been awarded the inaugural “Ocean Observing Team Award” by The Oceanography Society (TOS). This award recognizes innovation and excellence in sustained ocean observing for scientific and practical applications. The WBTS/RAPID/MOCHA team is recognized for significantly improving our understanding of Atlantic circulation through the breakthrough design of a basin-wide observing system using endpoint measurements to measure the variability of the overturning circulation across wide areas of the ocean. This design provided continuous, cost-effective measurements that led to a transformation in ocean observing and advances in scientific knowledge.
First-ever Daily Time Series Reveals the Strength of the Deep Ocean Circulation in the South Atlantic
In a recent study published in the journal Science Advances, oceanographers at AOML and the Cooperative Institute for Marine and Atmospheric Studies for the first time describe the daily variability of the circulation of key deep currents in the South Atlantic Ocean that are linked to climate and weather. The study found that the circulation patterns in the upper and deeper layers of the South Atlantic often vary independently of each other, an important new result about the broader Meridional Overturning Circulation (MOC) in the Atlantic.
AOML is preparing to deploy two autonomous data pod systems with Pressure Inverted Echo Sounders near the eastern boundary of the North Atlantic during March 2020. This will be the first full scale operational deployment of data pods, with a goal of providing a low-cost solution for the sustained Atlantic Meridional Overturning Circulation monitoring without the continuous use of a research vessel.
New Study Shows Atlantic Meridional Overturning Circulation and Mediterranean Sea Level are Connected
The global mean sea level rise caused by ocean warming and glacier melting over landforms such as Greenland is one of the most alarming aspects of a shifting global climate. However, the dynamics of the ocean and atmosphere further influence sea level changes region by region and over time. For example, along the U.S. East Coast, a pronounced acceleration of sea level rise in 2010-2015 was observed south of Cape Hatteras, while a deceleration occurred up North. These patterns provide background conditions, on top of which shorter-period (and often stronger) weather-driven sea level fluctuations compound what coastal communities directly experience day by day. Therefore, to develop or improve regional sea level predictions, it’s important to identify these patterns and explore how they change over time.
Ocean tracers such as heat, salt and carbon are perpetually carried by the global meridional overturning circulation (GMOC) and redistributed between hemispheres and across ocean basins from their source regions. The GMOC is therefore a crucial component of the global heat, salt and carbon balances.
AOML oceanographers Christopher Meinen and Molly Baringer participated in the development of a new thirteen-year-long record of the daily Atlantic ocean overturning that has recently been released. This project is a collaboration between a large team of researchers at NOAA, at the University of Miami ,and at the National Oceanography Centre in Southampton, United Kingdom.
There have been many efforts to understand the role of the Atlantic Meridional Overturning Circulation (AMOC) as a potential predictor of decadal climate variability, motivated partly by its inherent relationship with North Atlantic sea surface temperature. In contrast, there is currently limited knowledge about the underlying mechanisms that govern the South Atlantic Meridional Overturning Circulation (SAMOC) variability and how it might feedback into climate, partly due to the small number of direct observations in this ocean basin.
Recent studies have suggested the possibility of the southern origin of the Atlantic MHT anomalies. These studies have used General Circulation Models (GCMs) to demonstrate covariability between the South Atlantic MOC (SAMOC) and the Southern Hemisphere westerlies at interannual to longer time scales. However, it has been pointed out that the sensitivity of the SAMOC to the changes in the Southern Hemisphere westerlies depends critically on the representation of mesoscale eddies in those models.
“Much of the work on the cause of Antarctic sea ice over recent decades has focused on atmospheric drivers but this paper focuses on the ocean’s role. The authors analyse the trend of Antarctic sea ice over the past 35 years on the basis of satellite data and model simulations forced with atmospheric reanalysis products. Their findings suggest that ocean processes play a crucial role in determining the seasonality of sea ice trends. They also reveal that the sea-ice response is regional.”
The Atlantic Meridional Overturning Circulation (AMOC) transports the upper warm water northward and the deep cold water southward in the Atlantic, and is a key component of the global energy balance. In many of the climate models that participate the Coupled Model Inter-comparison Project Phase 5 (CMIP5), the amplitudes of the AMOC agree very well with or are even larger than the observed value of about 18 Sv at 26.5N; but they still show cold upper ocean temperature biases in the North Atlantic.