Tier 2 Land–Ocean Warming Contrast

2 figures · 1990–2014 → 2040–2049

Synthesis

While IFS-FESOM and IFS-NEMO maintain a nearly identical land-ocean warming ratio (~1.55), the FESOM configuration yields significantly higher absolute warming and distinct Southern Ocean cooling anomalies compared to NEMO.
Under the SSP3-7.0 scenario, the IFS-FESOM and IFS-NEMO configurations exhibit a remarkably consistent land-ocean warming ratio (1.54 and 1.55, respectively) for the 2040–2049 period relative to 1990–2014, despite significant divergence in bulk climate sensitivity. IFS-FESOM predicts a notably warmer future state with global terrestrial anomalies averaging +1.83 K compared to +1.40 K in IFS-NEMO, driven by a 32% higher oceanic warming rate. This indicates that while the shared atmospheric component (IFS) dictates the fundamental energy partitioning via moisture limitations and sensible heat flux, the choice of ocean coupling (unstructured FESOM vs. structured NEMO) strongly influences total system heat uptake and transient climate response. Spatially, both models resolve characteristic high-resolution features, including strong Arctic amplification (exceeding 4 K saturation) and a distinct North Atlantic 'warming hole' suggestive of AMOC weakening. However, the models diverge in polar regions: IFS-FESOM simulates a generally warmer Northern Hemisphere and unique cooling in the Pacific sector of the Southern Ocean, which is absent in IFS-NEMO. These regional discrepancies imply that differences in grid discretization and mixed-layer physics significantly modulate sea-ice albedo feedbacks and Southern Ocean heat uptake, even as the global land-sea contrast remains structurally robust.

Related diagnostics

arctic_amplification amoc_timeseries sea_ice_extent

Land-Ocean Warming Contrast

Land-Ocean Warming Contrast
Variables avg_2t, avg_tos
Models ifs-fesom, ifs-nemo
Units K
Baseline 1990-2014
Future 2040-2049
Method Ocean mask from SST availability; ΔT from avg_2t. Ratio = ΔT_land / ΔT_ocean.

Summary high

This diagnostic quantifies the differential warming between land and ocean surfaces for IFS-FESOM and IFS-NEMO under the SSP3-7.0 scenario (2040-2049 vs 1990-2014), revealing consistent terrestrial amplification despite differing bulk sensitivities.

Key Findings

  • IFS-FESOM predicts significantly higher absolute warming, with land temperature increasing by ~1.83 K compared to ~1.40 K in IFS-NEMO.
  • The land-ocean warming ratio is remarkably robust across the two ocean couplings, annotated as 1.54 for IFS-FESOM and 1.55 for IFS-NEMO.
  • Oceanic warming in IFS-FESOM (~1.19 K) is approximately 32% higher than in IFS-NEMO (~0.90 K), driving the overall higher global mean temperature.

Spatial Patterns

While spatially aggregated, the data confirms the global terrestrial amplification pattern where limited moisture availability for evaporative cooling over land leads to greater sensible heating compared to the ocean.

Model Agreement

The models show high agreement on the partitioning of warming (the L/O ratio), suggesting the atmospheric driver (IFS) largely sets the contrast physics. They disagree on the total system heat uptake, with the FESOM configuration yielding a higher Transient Climate Response (TCR) than the NEMO configuration.

Physical Interpretation

The warming contrast (L/O > 1) results from the ocean's infinite moisture supply allowing energy dissipation via latent heat flux, and its higher thermal inertia. The divergence in absolute warming likely stems from differences in ocean heat uptake efficiency or sea-ice albedo feedbacks between the FESOM (unstructured) and NEMO (structured) grids.

Caveats

  • ICON model data is absent from this specific comparison.
  • Global averages may mask regional disparities, particularly differences in polar amplification driven by distinct sea-ice physics in FESOM versus NEMO.
  • The 2040-2049 window represents a transient climate state; equilibrium ratios may differ.

Temperature Change Map

Temperature Change Map
Variables avg_2t
Models ifs-fesom, ifs-nemo
Units K
Baseline 1990-2014
Future 2040-2049
Method Future mean minus historical mean of avg_2t.

Summary high

The figure illustrates the projected 2-meter temperature change between the 2040s (SSP3-7.0) and the 1990-2014 baseline for IFS-FESOM and IFS-NEMO, revealing a classic global warming signature dominated by Arctic amplification and land-sea contrast.

Key Findings

  • Pronounced Arctic Amplification is evident in both models, with warming exceeding the 4 K saturation scale over the Arctic Ocean and adjacent high-latitude land masses.
  • A distinct 'warming hole' (local cooling of ~0.5 to 2 K) is visible in the subpolar North Atlantic south of Greenland in both simulations.
  • IFS-FESOM predicts a generally warmer Northern Hemisphere compared to IFS-NEMO, particularly over Eurasian land masses and the North Pacific.
  • The Southern Ocean exhibits delayed warming, with IFS-FESOM explicitly showing a region of cooling in the Pacific sector which is absent in IFS-NEMO.

Spatial Patterns

Both models show strong zonal asymmetry. Continents warm significantly faster (2–4 K) than oceans (0.5–1.5 K). The strongest positive anomalies (>4 K) are concentrated in the Arctic Basin, Barents-Kara Seas, and Northern Canada/Siberia. Conversely, the subpolar North Atlantic shows a localized negative anomaly (cooling). The Southern Ocean shows minimal warming, with specific cooling pockets near Antarctica in the IFS-FESOM simulation.

Model Agreement

The models agree on the broad structural response to forcing: polar amplification, land-sea contrast, and the North Atlantic warming hole. However, IFS-FESOM appears more sensitive, showing higher magnitude warming over Northern Hemisphere continents and broader Arctic warming. A notable disagreement exists in the Southern Ocean (Pacific sector), where IFS-FESOM simulates cooling (blue), while IFS-NEMO simulates weak warming (pale orange). This may stem from differences in sea-ice coupling or mixed-layer physics between the FESOM (unstructured grid) and NEMO ocean models.

Physical Interpretation

The patterns are driven by well-understood coupled mechanisms: 1) Arctic amplification results from the sea-ice albedo feedback and lapse-rate feedback; 2) The North Atlantic warming hole is a signature of a weakening Atlantic Meridional Overturning Circulation (AMOC), reducing northward heat transport; 3) The land-sea contrast arises from the lower heat capacity of land and limited evaporative cooling compared to the ocean; 4) Southern Ocean delay is due to deep mixing and upwelling of cold, deep waters.

Caveats

  • The color bar saturates at ±4 K, masking the full magnitude of Arctic warming which likely exceeds this limit.
  • The 10-year averaging period (2040-2049) may still contain internal decadal variability, particularly in the North Atlantic and Southern Ocean, potentially influencing the exact shape of the cooling anomalies.
  • Differences in the 'warming hole' morphology may depend on the specific grid resolution and representation of deep convection in the Labrador/Irminger Seas.