Impacts on Ocean Heat from Transient Mesoscale Eddies in a Hierarchy of Climate Models

Abstract

The authors characterize impacts on heat in the ocean climate system from transient ocean mesoscale eddies. Their tool is a suite of centennial-scale 1990 radiatively forced numerical climate simulations from three GFDL coupled models comprising the Climate Model, version 2.0–Ocean (CM2-O), model suite. CM2-O models differ in their ocean resolution: CM2.6 uses a 0.1° ocean grid, CM2.5 uses an intermediate grid with 0.25° spacing, and CM2-1deg uses a nominal 1.0° grid. Analysis of the ocean heat budget reveals that mesoscale eddies act to transport heat upward in a manner that partially compensates (or offsets) for the downward heat transport from the time-mean currents. Stronger vertical eddy heat transport in CM2.6 relative to CM2.5 accounts for the significantly smaller temperature drift in CM2.6. The mesoscale eddy parameterization used in CM2-1deg also imparts an upward heat transport, yet it differs systematically from that found in CM2.6. This analysis points to the fundamental role that ocean mesoscale features play in transient ocean heat uptake. In general, the more accurate simulation found in CM2.6 provides an argument for either including a rich representation of the ocean mesoscale in model simulations of the mean and transient climate or for employing parameterizations that faithfully reflect the role of eddies in both lateral and vertical heat transport.

An extreme event of sea-level rise along the Northeast coast of North America in 2009–2010

“…This correlation suggests that a 30% weakening of the AMOC in 2009-2010 may have contributed to and increased the chance of extreme coastal SLR events. The two models with eddying oceans (GFDL CM2.6 and CM2.5) show weaker correlation, probably due to the relatively weak AMOC in these two models 32 ( Supplementary Fig. 9).…”

“…To better understand extreme SLR events in this region, we use two sets of state-of-the-art climate models: an ensemble of ten models developed at GFDL, including high-resolution models with eddying oceans 32 (Table 2), and the other set including 14 CMIP5 models with the AMOC and sea-level data available at the CMIP5 archive 33 (Table 3; also see the Methods section). The GFDL ensemble represents different model generations with progressive improvement and a systematic model development effort at one modelling centre.…”

“…27) contributes to the extreme SLR event both remotely and locally. First, the negative NAO can cause an anomalous heat flux 44 Griffies et al 32 Winton et al 45 CM2.5 0.5°0.25°, z* coordinate Delworth et al 44 Griffies et al 32 Winton et al 45 CM2.5FLORa6 0.5°1°, z* coordinate Vecchi et al 46 Griffies et al 32 Winton et al 45 CM2.5FLOR 0.5°1°, z* coordinate Vecchi et al 46 Griffies et al 32 Winton into the Labrador Sea, thereby influencing the AMOC and SLR along the NE coast of North America ( Supplementary Fig. 5).…”

Response of O<sub>2</sub> and pH to ENSO in the California Current System in a high-resolution global climate model

“…In contrast to GFDL's publicly released models that undergo years of iterative development and analysis to assure fidelity to a suite of observational metrics, ESM2.6 was implemented as a single test simulation as proof of concept. ESM2.6 was built upon the highresolution CM2.6 physical climate model (Delworth et al, 2012;Griffies et al, 2015;Saba et al, 2016). The model's ocean component is GFDL's Modular Ocean Model version 5 (MOM5; Griffies, 2012) with a horizontal resolution of 0.1 • and 50 vertical layers.…”

The Flux-Anomaly-Forced Model Intercomparison Project (FAFMIP) contribution to CMIP6: investigation of sea-level and ocean climate change in response to CO<sub>2</sub> forcing

“…Such ocean process-based diagnostics have previously been included in only a small number of models (e.g. Gregory, 2000;Huang et al, 2003;Morrison et al, 2013Morrison et al, , 2016Palter et al, 2014;Exarchou et al, 2015;Griffies et al, 2015;Kuhlbrodt et al, 2015), and cannot be estimated accurately from other archived data. The FAFMIP experiments and diagnostics will for the first time permit us to attribute differences in the ocean among a wide range of models in the unperturbed state and in CO 2 -forced climate change to particular processes and aspects of model formulation.…”