Tier 1 Surface Energy Balance
Synthesis
Related diagnostics
Latent Heat Flux Change
| Variables | avg_slhtf |
|---|---|
| Models | ifs-fesom, ifs-nemo |
| Units | W/m2 |
| Baseline | 1990-2014 |
| Future | 2040-2049 |
| Method | Future mean minus historical mean. |
Summary high
The figure illustrates the projected change in surface latent heat flux (SLHF) between the 1990-2014 baseline and the 2040-2049 period under SSP3-7.0 for IFS-FESOM and IFS-NEMO. Both models project enhanced evaporation over western boundary currents and reduced fluxes in subpolar gyres, consistent with expected SST warming patterns and circulation changes.
Key Findings
- A distinct dipole in the North Atlantic, with increased latent heat flux (up to +20 W/m²) along the Gulf Stream extension and decreased flux (-10 to -20 W/m²) in the subpolar gyre and Nordic Seas.
- Strong local increases in SLHF along the sea-ice margins in the Arctic and parts of the Southern Ocean, indicative of sea-ice retreat exposing warmer water.
- Notable disagreement in terrestrial evapotranspiration signals over South America, where IFS-FESOM predicts a large region of increased flux (drying/warming signal) compared to IFS-NEMO.
- Broad decreases in SLHF in the high-latitude North Pacific and bands of the Southern Ocean.
Spatial Patterns
Oceanic patterns are characterized by positive anomalies (red) in the subtropics and western boundary current extensions (Gulf Stream, Kuroshio), and negative anomalies (blue) in high-latitude subpolar gyres. The North Atlantic exhibits a 'warming hole' signature with reduced evaporation south of Greenland. Over land, patterns are heterogeneous; IFS-FESOM shows strong positive anomalies over Eastern Brazil and parts of the Sahel, whereas IFS-NEMO shows negative anomalies in Central Africa. High Arctic regions show localized intense positive anomalies corresponding to sea ice loss.
Model Agreement
The models show high structural agreement over the oceans, particularly regarding the North Atlantic dipole and the Southern Ocean zonal banding. Discrepancies are most pronounced over tropical landmasses (Amazonia, Central Africa) and in the fine-scale structure of the Agulhas Return Current, likely stemming from differences in ocean grid geometry (unstructured vs. structured) affecting SSTs and subsequent atmospheric coupling.
Physical Interpretation
The widespread increases in SLHF in the subtropics and mid-latitudes are driven by rising Sea Surface Temperatures (SSTs) and the Clausius-Clapeyron relation increasing atmospheric demand. The negative anomalies in the North Atlantic subpolar gyre suggest a reduced air-sea temperature gradient, consistent with a slowdown of the Atlantic Meridional Overturning Circulation (AMOC) leading to relative SST cooling (the 'warming hole'). High-latitude increases correspond to sea-ice retreat, allowing ocean-to-atmosphere heat transfer. Discrepancies over land likely reflect differing precipitation response and soil moisture feedbacks induced by the coupled ocean states.
Caveats
- The analysis relies on a 10-year future mean (2040-2049), which may be influenced by decadal internal variability (e.g., ENSO, IPO) in addition to the forced climate signal.
- Land surface scheme differences or sensitivities to coupled precipitation biases may exaggerate the divergence in terrestrial evapotranspiration signals.
Surface Downward LW Radiation Change
| Variables | avg_sdlwrf |
|---|---|
| Models | ifs-fesom, ifs-nemo |
| Units | W/m2 |
| Baseline | 1990-2014 |
| Future | 2040-2049 |
| Method | Future mean minus historical mean. |
Summary high
The figure illustrates the projected change in Surface Downward Longwave Radiation (SDLWR) between the historical baseline (1990-2014) and the mid-century (2040-2049) under SSP3-7.0, showing a globally ubiquitous increase driven by the enhanced greenhouse effect and water vapor feedback.
Key Findings
- A global increase in downward longwave radiation is observed, ranging generally from +5 to +20 W/m², with land masses exhibiting stronger increases than most ocean basins.
- The most pronounced signal occurs in the Arctic (Barents-Kara Sea region), where anomalies exceed +20 W/m², indicative of strong sea-ice loss feedbacks.
- Strong positive anomalies are also evident along the Gulf Stream extension and in major continental arid/semi-arid regions (e.g., North Africa, Mediterranean, Australia).
Spatial Patterns
The spatial distribution shows a clear land-sea contrast, with continental interiors (particularly the Northern Hemisphere) showing increases of 10–18 W/m². In the Arctic, a distinct 'hotspot' corresponds to the retreat of sea ice, leading to warmer surface air temperatures and increased atmospheric moisture. Oceanic patterns reveal enhanced radiation along the Gulf Stream and Kuroshio extensions. Conversely, the Southern Ocean displays the weakest positive anomalies (~0–5 W/m²), with localized neutral patches near the Antarctic coast.
Model Agreement
Agreement between IFS-FESOM and IFS-NEMO is exceptionally high, which is expected as they share the same IFS atmospheric component. Minor discrepancies exist in the marginal ice zones (e.g., localized intensity differences in the Barents Sea) and the structural definition of the Gulf Stream front, reflecting differences in the underlying ocean model grids (unstructured FESOM vs. structured NEMO) and their representation of sea surface temperatures and ice cover.
Physical Interpretation
The pervasive increase is primarily driven by rising atmospheric temperatures and specific humidity (water vapor feedback), which increase the effective emissivity of the atmosphere. The intense Arctic signal results from the sea-ice albedo feedback: receding ice exposes warmer ocean water, heating the overlying atmosphere and increasing cloudiness/moisture, which strongly re-radiates longwave energy downwards. The land-sea contrast arises because land surfaces warm faster than the ocean, heating the planetary boundary layer more effectively.
Caveats
- The analysis considers only the downward longwave component; changes in net radiation will depend on opposing trends in shortwave radiation (e.g., due to cloud cover changes).
- The 5-km grid resolution suggests these models resolve mesoscale atmospheric features, but the radiative transfer parameterizations remain approximations.
Surface Downward SW Radiation Change
| Variables | avg_sdswrf |
|---|---|
| Models | ifs-fesom, ifs-nemo |
| Units | W/m2 |
| Baseline | 1990-2014 |
| Future | 2040-2049 |
| Method | Future mean minus historical mean. |
Summary high
The figure illustrates the projected change in surface downward shortwave radiation (2040–2049 vs 1990–2014) under SSP3-7.0, characterized by pronounced hemispheric asymmetries and strong regional contrasts driven by cloud cover changes.
Key Findings
- Significant 'brightening' (increase in downward SW > 6 W/m²) observed over the Amazon Basin, Europe, and the Mediterranean, indicating reduced cloud cover.
- Widespread 'dimming' (decrease in downward SW > 6 W/m²) over the Arctic Ocean, North Atlantic subpolar gyre, and the Indian subcontinent.
- Distinct zonal bands of reduced radiation along the ITCZ in the tropical Pacific and Atlantic, contrasted by increases in the subtropics.
Spatial Patterns
A clear land-sea contrast is visible in the mid-latitudes, particularly over Europe (positive anomaly) versus the North Atlantic (negative anomaly). The Arctic shows a coherent, basin-wide reduction in surface solar radiation. In the tropics, the pattern is dominated by shifts in convergence zones, with the Indian Ocean and South Asia showing strong negative anomalies likely associated with monsoon intensification or aerosol loading.
Model Agreement
Both IFS-FESOM and IFS-NEMO exhibit high consistency in large-scale patterns, particularly the Amazonian drying signal and Arctic dimming. However, IFS-NEMO displays sharper, more zonally coherent structures in the tropical Pacific ITCZ region and a more pronounced positive anomaly in the South Pacific subtropical gyre compared to IFS-FESOM, likely due to differences in ocean circulation solving (structured vs. unstructured grids) affecting SSTs and overlying convection.
Physical Interpretation
The patterns are primarily driven by cloud feedbacks. In the Arctic, sea-ice loss leads to increased surface evaporation and low-level stratus formation, reducing incoming solar radiation (negative feedback). Over the Amazon and Europe, projected drying and anticyclonic circulation anomalies reduce cloud fraction, increasing surface SW (positive feedback). The negative anomalies over India and the ITCZ suggest enhanced deep convection and optical depth.
Caveats
- The 10-year future averaging period (2040-2049) is relatively short, meaning internal decadal variability (e.g., ENSO phases) could influence the tropical patterns.
- Disentangling the direct radiative effect of changing aerosol burdens from cloud adjustments is not possible from this diagnostic alone.
Sensible Heat Flux Change
| Variables | avg_ishf |
|---|---|
| Models | ifs-fesom, ifs-nemo |
| Units | W/m2 |
| Baseline | 1990-2014 |
| Future | 2040-2049 |
| Method | Future mean minus historical mean. |
Summary high
The figure illustrates the projected change in surface sensible heat flux (SHF) between the future (2040-2049) and historical (1990-2014) periods under the SSP3-7.0 scenario for two high-resolution coupled models, IFS-FESOM and IFS-NEMO. The results show strong consistency between models, characterised by enhanced upward heat flux over retreating sea-ice zones and drying land regions, contrasted with reduced sensible heat flux over the Amazon and parts of the mid-latitude continents.
Key Findings
- Sea-ice retreat in the Southern Ocean and Arctic (Barents/Kara Seas) leads to strong positive SHF anomalies (>6 W/m²), indicating increased heat loss from the newly exposed open ocean to the atmosphere.
- A distinct dipole response is evident over tropical landmasses: Central Africa and India exhibit increased SHF (red), while the Amazon Basin and parts of Southeast Asia show decreased SHF (blue).
- Western Boundary Currents (Gulf Stream and Kuroshio extensions) show bands of increased sensible heat flux, suggesting these regions remain hotspots for ocean-to-atmosphere heat transfer in a warming climate.
- IFS-FESOM and IFS-NEMO show remarkably similar spatial patterns and magnitudes, indicating that the atmospheric component (IFS) dominates the surface flux response or that both ocean models resolve similar frontal dynamics.
Spatial Patterns
The Southern Ocean displays a zonal band of strong positive anomalies surrounding Antarctica, coincident with the marginal ice zone. Over land, large-scale coherent structures are visible: widespread positive anomalies over the Sahel, Southern Africa, India, and Western Australia, contrasted with negative anomalies over the Amazon, Eastern United States, and Eastern Australia. In the North Atlantic, a positive anomaly tracks the Gulf Stream path, while the subpolar gyre shows mixed signals.
Model Agreement
Agreement is high. The spatial patterns over land are virtually identical, which is expected as both configurations share the IFS atmospheric component and land surface scheme. Ocean patterns are also highly consistent, including the structure of anomalies in the energetic Western Boundary Currents and the Southern Ocean, suggesting robust coupling responses despite the different ocean dynamical cores (unstructured FESOM vs. structured NEMO).
Physical Interpretation
Positive anomalies over oceans, particularly at high latitudes, are driven by sea-ice loss (removing insulation) and SST warming maintaining a positive sea-air temperature differential. Over land, the response is likely governed by the Bowen ratio; regions like Central Africa and India likely experience drying (reduced soil moisture), suppressing latent heat flux and forcing energy dissipation via sensible heat. Conversely, the negative anomalies in the Amazon and Eastern US suggest either increased precipitation (shifting energy to latent heat) or a faster warming of the overlying air relative to the surface, reducing the upward temperature gradient.
Caveats
- The analysis assumes a 'positive upwards' sign convention for sensible heat flux, consistent with the physics of sea-ice retreat signals.
- The 10-year averaging period (2040-2049) may still contain internal decadal variability (e.g., ENSO, IPO) that could modulate regional patterns, particularly over the Pacific and Southern Oceans.
- The figure does not explicitly separate contributions from surface temperature changes versus wind speed changes.
Surface Net LW Radiation Change
| Variables | avg_snlwrf |
|---|---|
| Models | ifs-fesom, ifs-nemo |
| Units | W/m2 |
| Baseline | 1990-2014 |
| Future | 2040-2049 |
| Method | Future mean minus historical mean. |
Summary high
The figure illustrates the projected change in surface net longwave (LW) radiation between the future (2040–2049, SSP3-7.0) and historical (1990–2014) periods for IFS-FESOM and IFS-NEMO models. The global pattern generally shows positive anomalies (increased net energy intake or reduced loss) in the tropics and subtropics, contrasted with negative anomalies (increased net energy loss) over sea-ice retreat zones and specific continental regions.
Key Findings
- Widespread positive net LW change (+2 to +6 W/m²) dominates the tropics and subtropics (e.g., Sahara, Indian Ocean), indicating that increases in atmospheric downwelling radiation (greenhouse effect/humidity) outpace the increase in surface upwelling radiation.
- Strong negative anomalies (down to -6 W/m²) are observed in the North Atlantic (Labrador/Greenland/Nordic Seas) and Southern Ocean sea-ice margins, consistent with sea-ice retreat exposing warmer open water.
- Continental regions such as the Central US, Amazon Basin, and parts of Europe show negative anomalies, suggesting strong surface warming (increased upward emission) possibly combined with reduced cloud cover or humidity (limited downward increase).
- IFS-FESOM displays sharper, more structured anomalies in the North Atlantic sea-ice zone compared to the slightly more diffuse patterns in IFS-NEMO.
Spatial Patterns
A clear latitudinal contrast exists: the tropics and subtropics are predominantly positive (red), while localized negative patches (blue) appear in the high-latitude oceans and mid-latitude continental interiors. Notable features include the intense positive anomaly over the Arabian Peninsula and the dipole-like negative structures in the North Atlantic subpolar region.
Model Agreement
The models exhibit very high agreement over land and most ocean basins, which is expected as they share the same IFS atmospheric physics. Discrepancies are primarily confined to the North Atlantic and Arctic marginal ice zones, reflecting differences in the underlying ocean models (FESOM vs. NEMO) and their handling of sea-ice dynamics and deep convection.
Physical Interpretation
The signal represents the balance between increased surface emission (driven by surface warming, $\sigma T^4$) and increased atmospheric back-radiation (driven by higher CO$_2$ and water vapor). In the tropics, the water vapor feedback strengthens downwelling radiation significantly (positive net change). In sea-ice retreat zones, surface temperature rises drastically (phase change from ice to water), causing upwelling radiation to increase much faster than the atmospheric component, leading to a negative net change.
Caveats
- The 10-year averaging period (2040-2049) may still contain internal climate variability (e.g., ENSO, decadal Atlantic modes) that could influence regional magnitudes.
- Diagnostic does not explicitly separate changes in downwelling vs. upwelling components or clear-sky vs. cloud effects, requiring inference for mechanism attribution.
Surface Net SW Radiation Change
| Variables | avg_snswrf |
|---|---|
| Models | ifs-fesom, ifs-nemo |
| Units | W/m2 |
| Baseline | 1990-2014 |
| Future | 2040-2049 |
| Method | Future mean minus historical mean. |
Summary high
The figure illustrates the change in surface net shortwave radiation between 2040–2049 (SSP3-7.0) and 1990–2014, revealing distinct zonal asymmetry driven by surface albedo feedbacks in high latitudes and hydrological cycle reorganization in the tropics.
Key Findings
- Pronounced increases in net surface shortwave radiation (>6 W/m²) are observed across the Arctic Ocean and high-latitude land masses (Northern Canada, Siberia), indicative of sea-ice and snow cover loss.
- A strong dipole exists in the tropics: significant surface dimming (negative anomalies of -4 to -6 W/m²) over the African Sahel, South Asia, and the tropical Atlantic, contrasted with surface brightening (positive anomalies) over the Amazon Basin and Maritime Continent.
- The Southern Ocean exhibits widespread negative anomalies, consistent with projected increases in cloud fraction and optical depth in this region.
- Both IFS-FESOM and IFS-NEMO display remarkably consistent spatial structures, suggesting that the atmospheric model physics (IFS) dominates the radiative response over the specific ocean coupling method.
Spatial Patterns
The Northern Hemisphere high latitudes are dominated by positive anomalies (red), maximizing over the seasonal sea-ice zone and snow-covered land. In the tropics, a distinct band of negative anomalies (blue) stretches across Central Africa and the Northern Indian Ocean, likely tracking a shift or intensification of the Intertropical Convergence Zone (ITCZ) and South Asian Monsoon. Conversely, the Amazon and Mediterranean regions show positive anomalies, consistent with drying trends and reduced cloud cover.
Model Agreement
Agreement is high. Both models exhibit nearly identical patterns over land and major ocean basins. Minor discrepancies appear in the marginal ice zones (e.g., Greenland Sea) and the texture of anomalies in the Southern Ocean, likely attributable to differences in sea-ice handling and grid geometry between FESOM (unstructured) and NEMO (structured).
Physical Interpretation
In the Arctic, the signal is driven by the surface albedo feedback: melting ice and snow expose darker surfaces, increasing absorption. In the tropics, patterns are driven by changes in Cloud Radiative Effect (CRE). The 'dimming' over Africa and India suggests increased convective activity and cloud optical thickness (wet-get-wetter), while the 'brightening' over the Amazon implies reduced cloudiness due to drying and subsidence. The Southern Ocean dimming is linked to phase changes in clouds (more liquid water) and jet shifting.
Caveats
- The analysis period (2040–2049) is relatively short, meaning internal climate variability (e.g., ENSO, PDO phases) could superimpose on the forced climate signal.
- SSP3-7.0 includes high regional aerosol loading; without separate aerosol optical depth diagnostics, it is difficult to distinguish how much of the dimming over South Asia/Africa is due to cloud changes versus direct aerosol scattering.