Sea Ice in the Arctic continues to decline

Key take-aways:

On the 12th of September 2023, Arctic sea ice extent reached its annual minimum, reaching 3.9 million km², which is 1.7 million km² less compared to the long term average (1993-2010). This corresponds to a sea ice loss of 2.8 times the size of France (all regions).
In 2023, the September Arctic Sea ice volume minimum hit a historic record-low of 3 200 km³.
In September 2023, the Arctic sea ice extent ranks as the sixth lowest observed since the beginning of the satellite record.
The last 17 annual minimum Arctic sea ice extents are also the lowest 17 ever observed (since 1979).

Arctic Sea ice September lows

Arctic Sea Ice Concentration (%) from January to September 2023.

September 2023 sea ice extent

For 2023, Arctic Sea ice reached its minimum annual extent on12 September. There is a large decrease in sea ice cover in the Beaufort Gyre and along the Eurasian continent during northern hemisphere spring and summer periods. Routes of the Northwest Passage in the Canadian Archipelago appear largely ice free this year. Figure 1 highlights the Arctic Sea ice concentration for 12 September 2023 (in dark red), the year 2012 the lowest record ever observed (in orange), both well below the long-term average for 1993-2010 (in grey).

The historical record-lows for September annual sea ice extent minimums sit at:

2007: 3.7 million km²
2012: 3.2 million km² (the lowest ever observed)
2019: 3.8 million km²
2020: 3.4 million km²
2023: 3.9 million km²(the 6^th lowest ever observed)

Figure 1: Arctic sea ice concentration for 12 September of 2023 (dark red), 2012 (orange), 2020 (light red) and for the climatology 1993-2010 (grey). September 12 is the annual Arctic Sea ice minimum for 2023. Global 1/12° forecasting (Lellouche, 2018) and reanalysis (Lellouche, 2022). Source: Mercator Ocean International, Copernicus Marine Service.

This year continues the trend of alarming sea ice decline in the Arctic. For 12 September 2023, the sea ice extent reached 3.9 million km², this is 1.7 million km² below the long-term average (1993-2010 climatology). This corresponds to a sea ice loss of 2.8 times the size of France (all regions). Figure 2 shows sea ice extent anomalies, with the blue lines showing increases, and red showing decreases compared to the long-term average.

Figure 2: Arctic sea ice extent daily anomaly from 1993 to 2023 compared to the longer-term average 1993-2010 (climatology). Global 1/12° forecasting and reanalysis systems. Source: Mercator Ocean International, Copernicus Marine Service.

Significance of monitoring in September

Monitoring the Arctic and Antarctic Sea ice extent in September is crucial because it represents the annual minimum point for sea ice coverage in the Arctic and the maximum in the Antarctic (September/October). These measurements of minimum and maximums provide a vital indicator of the impact of climate change.

Arctic Sea Ice Volume

Arctic Sea Ice Volume (km3)

Unlike the Antarctic, where regular sea ice decline only started in 2016, the Arctic has been regularly losing sea ice since 1993. Figure 3 illustrates Arctic Sea ice volume over time, highlighting the record-low years of 2023 (dark red line), 2020 (light red line), and 2012 (orange line), that sit well below the long-term average (1993-2020).

Figure 3: Arctic Sea Ice volume over time between 1993 to 2023. The grey line represents the average for 1993-2020 (climatology). The dark red like shows the year 2023, the light red line 2020, the orange line 2012, and the light blue lines the remaining years between 1993 to 2023. Global 1/12° forecasting and reanalysis systems. Source: Mercator Ocean International, Copernicus Marine Service.

From 1993 to 2006, the September Sea ice volume minimum reached between 11 000 and 17 000 km³. Since 2007, the September Sea ice volume minimums descend to between 3 200 and 8 700 km³. The year 2007 was the first historical minimum with 7 100 km³.

New records for the September minimum Arctic Sea ice volume have been exceeded during the last years:

2007: 7 100 km³(first historical low)
2012: 4 200 km³
2020: 3 900, km³
2021: 3 400 km³
2022: 3 600 km³
2023 3 200 km³ (lowest on record)

This behaviour highlights the continuous loss of thicker and multi-year ice, in accordance with observations. Figure 4 illustrates sea ice volume anomalies, which describes the gain of sea ice in blue and loss in red as compared to the long term average (1993-2010 reference period).

Figure 4: Arctic sea ice volume daily anomaly from 1993-2023, as compared to the 1993-2010 mean reference period. Global 1/12° forecasting and reanalysis systems. Source: Mercator Ocean International, Copernicus Marine Service.

Declining Global Sea Ice Cover

This year there was a drastic drop in sea ice on a global scale caused by a combination of the now usual major melting during the northern hemisphere spring in the Arctic, and the significant lack of sea ice growth during the southern hemisphere autumn in the Antarctic. This global historical low sea ice extent decrease started in May and has continued, with sea ice cover in the two poles sitting between 20 and 22 million km² since then. Illustrated in figure 5, the total Arctic and Antarctic Sea ice extent for 2023 is the lowest on record for June, July, August, and September, respectively.

Figure 5: Arctic and Antarctic sea ice extent between 1993 to 2023. The dark red line represents the year 2023. Global 1/12° forecasting and reanalysis systems. Source: Mercator Ocean International, Copernicus Marine Service

Climate implications of global sea ice loss

The Earth’s albedo, or its ability to reflect sunlight, is heavily influenced by the extent of ice cover on the planet’s surface. Ice, with its high reflectivity, has a significant cooling effect on the Earth’s climate by bouncing a substantial portion of incoming solar radiation back into space. As global ice cover decreases due to climate change, more sunlight is absorbed by darker surfaces like water and land, potentially leading to increased warming, altered weather patterns, and exacerbating global climate change.

Further Resources :

Mercator Ocean Marine Heatwave Bulletin

Copernicus Marine products used:

GLORYS12V1 global ocean eddy-resolving (1/12° horizontal resolution, 50 vertical levels) reanalysis covering the altimetry (1993 onward). https://doi.org/10.48670/moi-00021
The Operational Mercator global ocean analysis and forecast system at 1/12 degree. https://doi.org/10.48670/moi-00016

References:

Zhang, L., Delworth, T.L., Yang, X. et al. The relative role of the subsurface Southern Ocean in driving negative Antarctic Sea ice extent anomalies in 2016–2021. Commun Earth Environ 3, 302 (2022). https://doi.org/10.1038/s43247-022-00624-1

Jean-Michel L, Eric G, Romain Bé-B, Gilles G, Angélique M, Marie D, Clément B, Mathieu H, Olivier LG, Charly R, Tony C, Charles-Emmanuel T, Florent G, Giovanni R, Mounir B, Yann D and Pierre-Yves LT (2021) The Copernicus Global 1/12° Oceanic and Sea Ice GLORYS12 Reanalysis. Front. Earth Sci. 9:698876. doi: 10.3389/feart.2021.698876

Lellouche, J.-M., Greiner, E., Le Galloudec, O., Garric, G., Regnier, C., Drevillon, M., Benkiran, M., Testut, C.-E., Bourdalle-Badie, R., Gasparin, F., Hernandez, O., Levier, B., Drillet, Y., Remy, E., and Le Traon, P.-Y.: Recent updates to the Copernicus Marine Service global ocean monitoring and forecasting real-time 1∕12° high-resolution system, Ocean Sci., 14, 1093–1126, https://doi.org/10.5194/os-14-1093-2018, 2018.