Tier 1 Surface Albedo

3 figures · 1990–2014 → 2040–2049

Synthesis

While models demonstrate strong consensus on widespread surface darkening across the Northern Hemisphere due to snow and ice retreat, they diverge significantly in the Weddell Sea, where IFS-FESOM predicts a localized albedo increase contrary to the global warming signal.
Under the SSP3-7.0 scenario (2040–2049 relative to 1990–2014), the high-resolution coupled models IFS-FESOM and IFS-NEMO exhibit a robust, hemispherically asymmetric reduction in surface albedo driven by the retreat of the cryosphere. Both models project widespread darkening (dimensionless anomalies < -0.04) across Northern Hemisphere marginal seas—specifically the Barents, Kara, and Hudson Bay—and high-latitude terrestrial regions, consistent with the surface albedo feedback mechanism where melting snow and sea ice expose darker underlying surfaces. IFS-FESOM projects a more intense albedo reduction in the North Atlantic sector, suggesting stronger sea ice retreat in that model compared to IFS-NEMO. Significant model discrepancies emerge in regional sea ice dynamics, particularly in the Southern Ocean. While IFS-NEMO predicts consistent albedo reductions in the Weddell Sea, IFS-FESOM displays a prominent positive anomaly (brightening), indicative of localized sea ice expansion or the cessation of deep convection events (polynya closure) specific to the unstructured FESOM grid formulation. Additionally, in the Arctic, IFS-NEMO simulates a localized region of positive albedo change north of the Canadian Archipelago—likely resulting from dynamic ice convergence—which is absent in the IFS-FESOM simulation.

Related diagnostics

sea_ice_concentration snow_cover_fraction mixed_layer_depth

Surface Albedo Change (Global)

Surface Albedo Change (Global)
Variables avg_snswrf, avg_sdswrf
Models ifs-fesom, ifs-nemo
Units W/m2
Baseline 1990-2014
Future 2040-2049
Method α = 1 − (net_SW / down_SW). Δα = α_future − α_historical.

Summary high

The figure displays projected surface albedo changes (2040-2049 vs 1990-2014) for IFS-FESOM and IFS-NEMO, revealing a dominant signal of surface darkening (albedo reduction) across the Northern Hemisphere cryosphere consistent with snow and ice loss. While both models agree on Arctic and terrestrial snow trends, they exhibit a stark contrast in the Southern Ocean, specifically the Weddell Sea.

Key Findings

  • Widespread albedo reduction (Δα < -0.04) across the Arctic Ocean, Barents Sea, and Greenland Sea, indicating significant sea ice retreat.
  • Consistent terrestrial albedo decrease over Northern Hemisphere high latitudes (Canada, Scandinavia, Russia) and mountain ranges (Andes, Himalayas), reflecting reduced seasonal snow cover.
  • A major discrepancy in the Weddell Sea (Southern Ocean): IFS-FESOM shows a strong increase in albedo (red patch), whereas IFS-NEMO shows a decrease (blue).

Spatial Patterns

The spatial response is hemispherically asymmetric. The Northern Hemisphere shows coherent high-latitude darkening over both ocean (sea ice loss) and land (snow retreat). The Southern Hemisphere response is confined to the Southern Ocean and Antarctic coast, with IFS-FESOM displaying a distinct dipole in the Weddell Sea that is absent in IFS-NEMO. Tropical and sub-tropical regions show negligible change.

Model Agreement

Models agree strongly on the sign and location of Northern Hemisphere changes, though IFS-FESOM suggests slightly more intense darkening in the North Atlantic sector. They disagree fundamentally in the Weddell Sea; IFS-FESOM's positive albedo anomaly suggests sea ice expansion or the closure of a historical open-ocean polynya, while IFS-NEMO predicts consistent sea ice decline.

Physical Interpretation

The dominant mechanism is the surface albedo feedback: warming leads to the melting of highly reflective sea ice and snow, exposing darker ocean water and vegetation/soil, which further absorbs solar radiation. The anomalous increase in the Weddell Sea in IFS-FESOM likely results from changes in ocean convection/stratification (e.g., a shutdown of deep convection leading to surface freshening and freezing) specific to the FESOM ocean formulation.

Caveats

  • The provided metadata lists units as W/m², but surface albedo is a dimensionless ratio (0-1); the color bar values (±0.04) correspond to dimensionless albedo changes.
  • The strong positive signal in the Weddell Sea in IFS-FESOM may represent model drift or internal variability (e.g., polynya dynamics) rather than a forced climate response.

Surface Albedo Change (North Polar)

Surface Albedo Change (North Polar)
Variables avg_snswrf, avg_sdswrf
Models ifs-fesom, ifs-nemo
Units W/m2
Baseline 1990-2014
Future 2040-2049
Method α = 1 − (net_SW / down_SW). Δα = α_future − α_historical.

Summary high

The figure illustrates projected surface albedo changes in the North Polar region for the period 2040–2049 relative to 1990–2014 under the SSP3-7.0 scenario, utilizing IFS-FESOM and IFS-NEMO coupled models. Both models simulate a widespread reduction in surface albedo (darkening) across high northern latitudes, consistent with the retreat of sea ice and terrestrial snow cover.

Key Findings

  • Widespread negative surface albedo anomalies (Δα < -0.04) are evident in both models, centered on marginal sea ice zones and high-latitude land masses.
  • Strongest albedo reductions occur in the Barents and Kara Seas, Hudson Bay, and Baffin Bay, indicating a transition from ice/snow-covered surfaces to open water.
  • IFS-FESOM projects a more spatially extensive and intense albedo reduction in the Barents Sea and North Atlantic subpolar region compared to IFS-NEMO.
  • IFS-NEMO displays a localized region of positive albedo change (brightening) north of the Canadian Archipelago/Greenland, which is absent in the IFS-FESOM result.

Spatial Patterns

The spatial distribution is dominated by dark blue patches (reductions > 0.04) in the seasonal sea ice zones (Hudson Bay, Labrador Sea, Barents/Kara Seas) and diffuse blue speckling over Northern Hemisphere land masses (Canada, Scandinavia, Russia) representing snow line retreat. The central Arctic Ocean shows weaker anomalies, likely due to persistent (though thinning) pack ice in the 2040s timeframe.

Model Agreement

The models agree on the primary sign of change (negative) and the broad geographical regions affected (marginal seas and snow-covered land). However, they disagree on the magnitude of sea ice loss in the Atlantic sector (Barents Sea), where IFS-FESOM suggests stronger 'Atlantification' or ice retreat. The divergence in the Central Arctic (IFS-NEMO showing brightening) suggests differences in sea ice dynamics (e.g., ice convergence/thickening) or internal variability arising from the different ocean grids (unstructured FESOM vs. structured NEMO).

Physical Interpretation

The patterns are driven by the surface albedo feedback mechanism: rising global temperatures cause melting of highly reflective sea ice and snow, exposing the darker ocean surface and soil/vegetation underneath. The distinct ocean signals highlight differences in the ocean/sea-ice component response to warming, particularly how sea ice edge retreat and advection are handled on the respective grids.

Caveats

  • The 10-year averaging period (2040–2049) is relatively short, meaning internal decadal variability could influence localized features like the positive anomaly in IFS-NEMO.
  • The metadata units (W/m2) are incorrect for albedo (a dimensionless ratio); the analysis assumes standard unitless albedo fractions.

Surface Albedo Change (South Polar)

Surface Albedo Change (South Polar)
Variables avg_snswrf, avg_sdswrf
Models ifs-fesom, ifs-nemo
Units W/m2
Baseline 1990-2014
Future 2040-2049
Method α = 1 − (net_SW / down_SW). Δα = α_future − α_historical.

Summary high

The figure illustrates projected surface albedo changes in the Southern Ocean for the 2040s (SSP3-7.0) relative to the 1990-2014 baseline, highlighting a stark divergence in the Weddell Sea response between the two IFS coupled configurations.

Key Findings

  • IFS-FESOM exhibits a large-scale, intense positive albedo anomaly (> +0.04) in the Weddell Sea, indicating a counter-intuitive increase in sea ice or snow cover.
  • IFS-NEMO predominantly shows negative albedo anomalies (decrease to -0.04) circum-Antarctica, consistent with widespread sea ice retreat.
  • Both models agree on significant albedo reductions in the Amundsen, Bellingshausen, and Ross Seas, as well as along the East Antarctic coast.

Spatial Patterns

A ring of negative albedo change (blue) characterizes the marginal ice zone in both models, marking the retreat of sea ice. The notable exception is the Weddell Sea gyre, where IFS-FESOM presents a cohesive area of increased albedo (red), whereas IFS-NEMO shows a fragmented pattern with dominant negative anomalies.

Model Agreement

Disagreement is high in the Weddell Sea sector, suggesting different handling of deep convection or sea ice dynamics in that gyre. Agreement is high regarding the sign of change (negative) in the Pacific and Indian Ocean sectors of the Southern Ocean.

Physical Interpretation

The pervasive negative anomalies are driven by the ice-albedo feedback: anthropogenic warming causes sea ice melt, exposing low-albedo open water. The anomalous positive signal in IFS-FESOM likely results from internal variability or a base-state bias shift—specifically, if the historical baseline simulation contained a frequent open-ocean polynya (low albedo) that is absent or reduced in the future projection, the relative increase in ice coverage would manifest as a positive albedo change.

Caveats

  • The strong positive signal in IFS-FESOM may represent the recovery from a historical-period bias (e.g., excessive polynya activity) rather than a forced response to SSP3-7.0.
  • The 10-year averaging period (2040-2049) preserves significant decadal variability, which may conflate with the long-term anthropogenic trend.