In and out. Driven by winds, the Southern Ocean's currents (blue globe) transport CO2 (red) northward. Credit: T. Ito et al., Nature 463 (2010)

story by Helen Hill

In this article we spotlight work by Taka Ito, Molly Woloszyn and Matt Mazloff who have been using MITgcm to study anthropogenic CO₂ transport in the Southern Ocean.

Key to their study is a high-resolution (1/6^o x 1/6^o) estimate of the Southern Ocean circulation, consistent with modern observations, deriving from an MITgcm adjoint calculation, developed as part of the ECCO-GODAE project.  In addition MITgcm’s offline model enabled a ready coupling of the high resolution circulation estimate to a carbon cycle model.

Focussing on intra-annual ACO₂ variability, the team found a clear correlation between the pattern of carbon uptake and oceanic vertical exchange in strong support of the wind-driven circulation as a primary regulator of Southern Ocean ACO₂ transport.

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Ecological Control of Subtropical Nutrient Concentrations

Figure 1: Multiple-Resource Experiment. (top) Emergent biogeographical provinces, defined by most dominant species, reminiscent of Longhurst (1995). (bottom) Biogeography of four major functional groups: (i) Diatom-analogs (red), (ii) other large phytoplankton (orange), (iii)Prochlorococcus-analogs (green), and (iv) other small phytoplankton (yellow-green).

In this article we spotlight recent work by Darwin Project team members Stephanie Dutkiewicz, Mick Follows and Jason Bragg, who have been examining the utility of resource control theory to interpret the relationships between organisms and resources in a global coupled physical-biogeochemistry-ecosystem model built around MITgcm.

The team find that in regions of low seasonality, resource competition theory (Tilman, ‘77)  not only anticipates the competitive outcome amongst organisms but also provides a quantitative diagnostic of ecological control of nutrient concentrations. DFB’s sensitivity experiments clearly indicate control on the ambient nutrient by phytoplankton physiology as predicted by the theory. Read the rest of this entry »

Figure 1: A snapshot of relative vorticity (in colors) and pressure (relief) at 100 m depth in a simulation with realistic, though idealized, forcing from an MITgcm simulation by Wolfe and Cessi . The color range spans =B15e-4 s^{-1}. The domain is a simple "notched box" ocean with vertical walls and periodic channel in the southernmost 1200 km.

Here we look at work of Christopher Wolfe and Paola Cessi at UCSD, in which they investigate the equilibrium response of an eddy-resolving version of MITgcm to variations in the external parameters of diffusivity, wind forcing and geometry, with particular attention to the meridional overturning circulation (MOC) and deep stratification.

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Planet-in-a-Bottle

Here we look at work by Sai Ravela, John Marshall, Chris Hill, Andrew Wong and Scott Stransky in which they use MITgcm to provide the virtual analogue for a fluid lab experiment in the physical laboratory, as part of an effort to demonstrate how to achieve real-time model-data synthesis, using measurements from a robotically controlled automated sensor system.

Figure 1. The components of the system: The laboratory observatory consists of a physical system: a rotating table on which a tank, camera and control system for illumination are mounted. The computational part consists of a measurement system for velocimetry, a numerical model (MITgcm), and an assimilation system.

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