Effects of Arctic sea-ice concentration on turbulent surface fluxes in four atmospheric reanalyses
<p>A prerequisite for understanding the local, regional, and hemispherical impacts of Arctic sea-ice decline on the atmosphere is to quantify the effects of sea-ice concentration (SIC) on the turbulent surface fluxes of sensible and latent heat in the Arctic. We analyse these effects utilising...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2024-03-01
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| Series: | The Cryosphere |
| Online Access: | https://tc.copernicus.org/articles/18/957/2024/tc-18-957-2024.pdf |
| _version_ | 1797289579320967168 |
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| author | T. Uhlíková T. Vihma A. Y. Karpechko P. Uotila |
| author_facet | T. Uhlíková T. Vihma A. Y. Karpechko P. Uotila |
| author_sort | T. Uhlíková |
| collection | DOAJ |
| description | <p>A prerequisite for understanding the local, regional, and hemispherical impacts of Arctic sea-ice decline on the atmosphere is to quantify the effects of sea-ice concentration (SIC) on the turbulent surface fluxes of sensible and latent heat in the Arctic. We analyse these effects utilising four global atmospheric reanalyses, ERA5, JRA-55, MERRA-2, and NCEP/CFSR (including both the NCEP Climate Forecast System Reanalysis (CFSR) and the NCEP Climate Forecast System Version 2 (CFSv2)), and evaluate their uncertainties arising from inter-reanalysis differences in SIC and in the sensitivity of the turbulent surface fluxes to SIC. The magnitude of the differences in SIC is up to 0.15 but typically around 0.05 in most of the Arctic over all four seasons. Orthogonal-distance regression and ordinary-least-squares regression analyses indicate that the greatest sensitivity of both the latent and the sensible heat flux to SIC occurs in the cold season, November to April. For these months, using daily means of data, the average sensitivity is 400 <span class="inline-formula">W m<sup>−2</sup></span> for the latent heat flux and over 800 <span class="inline-formula">W m<sup>−2</sup></span> for the sensible heat flux per unit of SIC (change in SIC from 0 to 1), with differences between reanalyses that are as large as 300 <span class="inline-formula">W m<sup>−2</sup></span> for the latent heat flux and 600 <span class="inline-formula">W m<sup>−2</sup></span> for the sensible heat flux per unit of SIC. The sensitivity is highest for the NCEP/CFSR reanalysis. Comparing the periods 1980–2000 and 2001–2021, we find that the effect of SIC on turbulent surface fluxes has weakened owing to the increasing surface temperature of sea ice and sea-ice decline. The results also indicate signs of a decadal-scale improvement in the mutual agreement between reanalyses. The effect of SIC on turbulent surface fluxes arises mostly via the effect of SIC on atmosphere–surface differences in temperature and specific humidity, whereas the effect of SIC on wind speed (via surface roughness and atmospheric-boundary-layer stratification) partly cancels out in the turbulent surface fluxes, as the wind speed increases the magnitudes of both upward and downward fluxes.</p> |
| first_indexed | 2024-03-07T19:07:09Z |
| format | Article |
| id | doaj.art-272318e23db746698b00fff9e963b9cd |
| institution | Directory Open Access Journal |
| issn | 1994-0416 1994-0424 |
| language | English |
| last_indexed | 2024-03-07T19:07:09Z |
| publishDate | 2024-03-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | The Cryosphere |
| spelling | doaj.art-272318e23db746698b00fff9e963b9cd2024-03-01T06:30:31ZengCopernicus PublicationsThe Cryosphere1994-04161994-04242024-03-011895797610.5194/tc-18-957-2024Effects of Arctic sea-ice concentration on turbulent surface fluxes in four atmospheric reanalysesT. Uhlíková0T. Vihma1A. Y. Karpechko2P. Uotila3Institute for Atmospheric and Earth System Research, Faculty of Science, University of Helsinki, 00014, Helsinki, FinlandFinnish Meteorological Institute, Helsinki, FinlandFinnish Meteorological Institute, Helsinki, FinlandInstitute for Atmospheric and Earth System Research, Faculty of Science, University of Helsinki, 00014, Helsinki, Finland<p>A prerequisite for understanding the local, regional, and hemispherical impacts of Arctic sea-ice decline on the atmosphere is to quantify the effects of sea-ice concentration (SIC) on the turbulent surface fluxes of sensible and latent heat in the Arctic. We analyse these effects utilising four global atmospheric reanalyses, ERA5, JRA-55, MERRA-2, and NCEP/CFSR (including both the NCEP Climate Forecast System Reanalysis (CFSR) and the NCEP Climate Forecast System Version 2 (CFSv2)), and evaluate their uncertainties arising from inter-reanalysis differences in SIC and in the sensitivity of the turbulent surface fluxes to SIC. The magnitude of the differences in SIC is up to 0.15 but typically around 0.05 in most of the Arctic over all four seasons. Orthogonal-distance regression and ordinary-least-squares regression analyses indicate that the greatest sensitivity of both the latent and the sensible heat flux to SIC occurs in the cold season, November to April. For these months, using daily means of data, the average sensitivity is 400 <span class="inline-formula">W m<sup>−2</sup></span> for the latent heat flux and over 800 <span class="inline-formula">W m<sup>−2</sup></span> for the sensible heat flux per unit of SIC (change in SIC from 0 to 1), with differences between reanalyses that are as large as 300 <span class="inline-formula">W m<sup>−2</sup></span> for the latent heat flux and 600 <span class="inline-formula">W m<sup>−2</sup></span> for the sensible heat flux per unit of SIC. The sensitivity is highest for the NCEP/CFSR reanalysis. Comparing the periods 1980–2000 and 2001–2021, we find that the effect of SIC on turbulent surface fluxes has weakened owing to the increasing surface temperature of sea ice and sea-ice decline. The results also indicate signs of a decadal-scale improvement in the mutual agreement between reanalyses. The effect of SIC on turbulent surface fluxes arises mostly via the effect of SIC on atmosphere–surface differences in temperature and specific humidity, whereas the effect of SIC on wind speed (via surface roughness and atmospheric-boundary-layer stratification) partly cancels out in the turbulent surface fluxes, as the wind speed increases the magnitudes of both upward and downward fluxes.</p>https://tc.copernicus.org/articles/18/957/2024/tc-18-957-2024.pdf |
| spellingShingle | T. Uhlíková T. Vihma A. Y. Karpechko P. Uotila Effects of Arctic sea-ice concentration on turbulent surface fluxes in four atmospheric reanalyses The Cryosphere |
| title | Effects of Arctic sea-ice concentration on turbulent surface fluxes in four atmospheric reanalyses |
| title_full | Effects of Arctic sea-ice concentration on turbulent surface fluxes in four atmospheric reanalyses |
| title_fullStr | Effects of Arctic sea-ice concentration on turbulent surface fluxes in four atmospheric reanalyses |
| title_full_unstemmed | Effects of Arctic sea-ice concentration on turbulent surface fluxes in four atmospheric reanalyses |
| title_short | Effects of Arctic sea-ice concentration on turbulent surface fluxes in four atmospheric reanalyses |
| title_sort | effects of arctic sea ice concentration on turbulent surface fluxes in four atmospheric reanalyses |
| url | https://tc.copernicus.org/articles/18/957/2024/tc-18-957-2024.pdf |
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