Tier 1 Arctic Amplification

2 figures · 1990–2014 → 2040–2049

Synthesis

Projected Arctic warming exceeds the global rate by a factor of 2.1 to 2.4 annually, peaking in winter due to sea-ice feedbacks, while contrasting with a distinct cooling hole in the North Atlantic.
Under the SSP3-7.0 scenario (2040–2049 relative to 1990–2014), the high-resolution IFS-FESOM and IFS-NEMO coupled models exhibit robust Arctic Amplification (AAF), with the Arctic warming significantly faster than the global mean. This amplification is highly seasonal: it peaks in Winter (DJF) and Autumn (SON) with factors between 2.86 and 3.35, driven by the release of stored ocean heat to the atmosphere through reduced sea-ice cover. In contrast, Summer (JJA) amplification is negligible (ratios ~1.06–1.09) as latent heat uptake during ice melting limits surface temperature rises. IFS-FESOM consistently predicts a stronger annual amplification (2.44) compared to IFS-NEMO (2.12), suggesting that the unstructured mesh formulation may simulate more aggressive sea-ice loss or enhanced ocean-to-atmosphere heat fluxes. Spatially, the warming signal (>4 K) is concentrated over the Central Arctic and the Barents-Kara sector, regions associated with the most dramatic sea-ice retreat and albedo reduction. A distinct North Atlantic Warming Hole (NAWH) south of Greenland disrupts this high-latitude warming pattern, showing localized cooling of 1–2 K in both models. This dipole—extreme Arctic warming contrasted with North Atlantic cooling—is a physical fingerprint of simultaneous sea-ice albedo feedback amplification and a weakening Atlantic Meridional Overturning Circulation (AMOC).

Related diagnostics

sea_ice_extent amoc_timeseries

Arctic Amplification Factor

Arctic Amplification Factor
Variables avg_2t
Models ifs-fesom, ifs-nemo
Units K
Baseline 1990-2014
Future 2040-2049
Method HealPix equal-area cells; .where(lat > 66.5).mean() for Arctic.

Summary high

The figure quantifies the Arctic Amplification Factor (AAF) for IFS-FESOM and IFS-NEMO under SSP3-7.0 (2040-2049 vs 1990-2014), revealing a pronounced seasonal cycle where Arctic warming exceeds the global average by 2-3 times in winter and autumn but is nearly equal to the global rate in summer.

Key Findings

  • Both models exhibit a strong seasonal asymmetry in amplification, peaking in Winter (DJF) and Autumn (SON) and reaching a minimum in Summer (JJA).
  • IFS-FESOM consistently predicts a higher AAF than IFS-NEMO across all periods, with the largest discrepancy in DJF (3.35 vs 2.86).
  • Summer (JJA) amplification is negligible (values ~1.06–1.09), indicating Arctic warming rates in summer tracks closely with the global mean.
  • Annual mean amplification is substantial, with the Arctic warming 2.44 times (IFS-FESOM) and 2.12 times (IFS-NEMO) faster than the global average.

Spatial Patterns

While the figure aggregates data spatially (Arctic cap vs. Globe), the high AAF values (>3 in DJF for FESOM) imply an intense spatial concentration of warming over the Arctic Ocean and high latitudes relative to the tropics and mid-latitudes during the cold season.

Model Agreement

The models qualitatively agree on the seasonal structure of amplification (DJF peak, JJA trough). However, they quantitatively disagree, with IFS-FESOM consistently simulating stronger polar amplification (approx. 15-17% higher annually). This likely stems from differences in the ocean-sea ice components (unstructured FESOM vs. structured NEMO) affecting sea-ice loss rates and ocean heat release.

Physical Interpretation

The seasonal cycle is driven by the sea-ice insulation and albedo feedbacks. In Summer (JJA), energy is consumed by latent heat of melting ice, keeping surface temperatures near freezing (AAF ~1). In Autumn (SON) and Winter (DJF), the reduced sea ice cover exposes the warmer ocean to the cold atmosphere, releasing stored heat, while the strong stable stratification of the polar atmosphere (lapse-rate feedback) traps this warming near the surface, driving high AAF.

Caveats

  • The ICON model is mentioned in the experiment context but is absent from this specific plot.
  • The metric (ratio) masks absolute temperature changes; differences could arise from variations in global sensitivity rather than just local Arctic physics.
  • Analysis period (2040-2049) is relatively short (10 years), making the signal potentially susceptible to internal decadal variability.

Arctic Warming Map

Arctic Warming 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

This figure illustrates the projected 2m temperature change in the Northern Hemisphere for the 2040–2049 period relative to 1990–2014 under the SSP3-7.0 scenario for the IFS-FESOM and IFS-NEMO coupled models.

Key Findings

  • Both models exhibit strong Arctic Amplification, with warming in the central Arctic Ocean exceeding 4 K, significantly outpacing mid-latitude warming.
  • A distinct North Atlantic Warming Hole (NAWH) is visible south of Greenland in both simulations, showing localized cooling of approximately 1–2 K.
  • The Barents-Kara Sea region shows the most intense warming signals, consistent with regions of projected rapid sea-ice loss.

Spatial Patterns

The warming is highly polar-amplified, with the strongest positive anomalies (>3 K) concentrated over the Arctic Ocean and adjacent high-latitude landmasses (Northern Eurasia and Northern Canada). A notable dipole exists in the North Atlantic, where the strong warming of the Nordic Seas contrasts sharply with the cooling anomaly (warming hole) in the subpolar gyre.

Model Agreement

IFS-FESOM and IFS-NEMO show high structural agreement regarding the location of the NAWH and the magnitude of continental warming (~2–3 K). However, IFS-FESOM predicts a slightly more spatially extensive and intense warming (>4 K) across the Central Arctic Basin compared to IFS-NEMO.

Physical Interpretation

The extreme warming over the Arctic Ocean is primarily driven by the sea-ice albedo feedback, where retreating ice exposes darker ocean water, enhancing heat absorption (particularly in the Barents-Kara sector). The cooling hole in the North Atlantic is a classic signature of a slowing Atlantic Meridional Overturning Circulation (AMOC), resulting in reduced northward heat transport.

Caveats

  • The analysis is based on annual means; seasonal decomposition is required to confirm if the Arctic warming is winter-dominant (heat release from open ocean).
  • The 10-year averaging period (2040–2049) is relatively short and may still contain signals from internal decadal variability.
  • ICON model mentioned in the system context is absent from this specific figure.