FAMOS-2: Beaufort Gyre Phenomenon
For details read: Proshutinsky, A., Krishfield, R., & Timmermans, M.‐L. (2019). Preface to special issue Forum for Arctic Ocean Modeling and Observational Synthesis (FAMOS) 2: Beaufort Gyre phenomenon. Journal of Geophysical Research: Oceans, 124. https://doi.org/10.1029/2019JC015400
One of the foci of the Forum for Artic Modeling and Observational Synthesis (FAMOS) project is improving Arctic regional ice-ocean models and understanding of physical processes regulating variability of Arctic environmental conditions based on synthesis of observations and model results. The Beaufort Gyre, centered in the Canada Basin of the Arctic Ocean, is an ideal phenomenon and natural laboratory for application of FAMOS modeling capabilities to resolve numerous scientific questions related to the origin and variability of this climatologic freshwater reservoir and flywheel of the Arctic Ocean. The unprecedented volume of data collected in this region is nearly optimal to describe the state and changes in the Beaufort Gyre environmental system at synoptic, seasonal and interannual time scales. The in situ and remote sensing data characterizing ocean hydrography, sea surface heights, ice drift, concentration and thickness, ocean circulation, and biogeochemistry have been used for model calibration and validation or assimilated for historic reconstructions and establishing initial conditions for numerical predictions.
The Journal of Geophysical Research special issue “FAMOS 2: Beaufort Gyre Phenomenon” (https://agupubs.onlinelibrary.wiley.com/doi/toc/10.1002/(ISSN)2169-9291.FAMOS2) described below contributes time series of the Beaufort Gyre data, new methodologies in observing, modeling and analysis; interpretation of measurements and model output, discussions and findings that shed light on the mechanisms regulating Beaufort Gyre dynamics as it transitions to a new state under different climate forcing.
Fresh water accumulation in the Beaufort Gyre region is a principal dynamical and thermo-dynamical process, reflecting numerous complicated relationships among the atmosphere, sea ice, ocean and ecosystems.
Recently, there has been a focus on explaining factors and mechanisms responsible for fresh water accumulation, release and saturation in the Beaufort Gyre region (e.g., based on observations: McLaughlin et al., 2011; Giles et al., 2012; Krishfield et al., 2014; Haine et al., 2015; and modeling: Nummelin et al., 2015; Lique et al., 2016; Marshall et al., 2017). The papers comprising this special issue continue these investigations using new observations, ideas and hypotheses to reveal mechanisms of changes and major factors influencing dynamics and thermodynamics of the Beaufort Gyre phenomenon.
Beaufort Gyre phenomenon: multicomponent system mechanisms and changes
The 2003–2019 time series of atmospheric, sea ice, oceanic, and biogeochemistry data, combined with Arctic coupled ice-ocean modeling with atmospheric forcing, have been used to: investigate the major causes, consequences and rates of Beaufort Gyre freshwater accumulation and release (e.g. Regan & Lique 2019; Proshutinsky et al., 2019b; Manucharyan & Isachen, 2019; Doddridge et al., 2019); identify the major sources of fresh water and the fresh water pathways from the sources to the Beaufort Gyre region (Kelly et al., 2019); explain the major patterns and regimes of the surface, Pacific and Atlantic water layer circulation (e.g. Hu & Mayers, 2019; Spall et al., 2019; Zhong et al., 2019); and reveal the physics of mechanical mixing and convection under the influence of wind, internal wave and tidal forcing (e.g. Zhao et al., 2018; Bebieve & Timmermans, 2019; Sibley and Timmermans, 2019; Chanona et al., 2019). Other papers in the collection examine the role of sea ice conditions, major features of ice variability and methods of sea ice prediction in the region (e.g. Persson et al., 2019; Babb et al. (2019); Mahoney et al., 2019; Lewis and Hutchings et al., 2019; Heorton et al., 2019; Yaremchuk et al., 2019). Ecosystem and biogeochemistry analysis targeting estimation of biological production rates in both water and sea ice, and characteristics of dissolved organic and inorganic matter are another focus, with papers employing synthesis of multi-model experiments in combination with collected data analysis (e.g. Ji et al., 2019; Dainard & Gueguen, 2019; DeGrandpre et al., 2019; Watanabe et al., 2019);
To explore the Beaufort Gyre in context with the broader Arctic, several papers describe processes of the relationship between the Beaufort Gyre and the northern Pacific and Atlantic Oceans, showing how the Beaufort Gyre region influences, and is influenced by, climate change including the increase of Greenland melt and modification of Atlantic water circulation (e.g. Dukhovskoy et al., 2019; Muilwijk et al., 2019a).
With a focus on modeling, there are several papers that employ a new approach using “climate response functions” to better understand processes of Arctic and subarctic variability and predict future Arctic change (e.g. Lambert et al., 2019; Muilwijk et al., 2019b). Below, some results of this special issue, with publications organized by discipline, theme and approach, are briefly summarized.
Causes and consequences of freshwater content variability
The causes and consequences of freshwater content changes are discussed by Proshutinsky et al. (2019b) in this special issue. The particular focus of Proshutinsky et al. (2019b) is an examination of the seasonal and interannual variability using year-round data from Ice-Tethered Profilers (ITPs), moorings and satellite data. The relative strengths and weakness of the different data sources for measuring Beaufort Gyre freshwater content are analyzed and the importance of having multiple diverse datasets to obtain a more comprehensive understanding of Beaufort Gyre freshwater content changes is shown. For example, annual BGOS hydrographic surveys clearly show the increase in freshwater content in the region; however, without satellite and ITP measurements it would not be possible to resolve the seasonal cycle, which is larger than year-to-year freshwater content variability. To better understand the observed variability in the region fresh water is differentiated by source (meteoric versus ice melt water) and by origin (water from Pacific, Eurasian or American rivers) in several coupled ice-ocean model runs with Lagrangian passive tracers released at the mouths of the Mackenzie and Siberian rivers and in Bering Strait. It was found that in 2003-2018, the major contributors of fresh water to the Beaufort Gyre were fresh waters coming from Bering Strait and the Mackenzie River.