Retrieval of Wintertime Sea Ice Production in Arctic Polynyas Using Thermal Infrared and Passive Microwave Remote Sensing Data

Precise knowledge of wintertime sea ice production in Arctic polynyas is not only required to enhance our understanding of atmosphere‐sea ice‐ocean interactions but also to verify frequently utilized climate and ocean models. Here, a high‐resolution (2‐km) Moderate Resolution Imaging Spectroradiometer (MODIS) thermal infrared satellite data set featuring spatial and temporal characteristics of 17 Arctic polynya regions for the winter seasons 2002/2003 to 2017/2018 is directly compared to an akin low‐resolution Advanced Microwave Scanning Radiometer‐EOS (AMSR‐E) passive microwave data set for 2002/2003 to 2010/2011. The MODIS data set is purely based on a 1‐D energy‐balance model, where thin‐ice thicknesses (≤ 20 cm) are directly derived from ice‐surface temperature swath data and European Centre for Medium‐Range Weather Forecasts Re‐Analysis‐Interim atmospheric reanalysis data on a quasi‐daily basis. Thin‐ice thicknesses in the AMSR‐E data set are derived empirically. Important polynya properties such as areal extent and potential thermodynamic ice production can be estimated from both pan‐Arctic data sets. Although independently derived, our results show that both data sets feature quite similar spatial and temporal variations of polynya area (POLA) and ice production (IP), which suggests a high reliability. The average POLA (average accumulated IP) for all Arctic polynyas combined derived from both MODIS and AMSR‐E are 1.99×105 km2 (1.34×103 km3) and 2.29×105 km2 (1.31×103 km3), respectively. Narrow polynyas in areas such as the Canadian Arctic Archipelago are notably better resolved by MODIS. Analysis of 16 winter seasons provides an evaluation of long‐term trends in POLA and IP, revealing the significant increase of ice formation in polynyas along the Siberian coast

北極域の海氷域変動が成層圏-対流圏結合に及ぼす影響とそのメカニズム

第6回極域科学シンポジウム分野横断セッション：[IA] 急変する北極気候システム及びその全球的な影響の総合的解明―GRENE北極気候変動研究事業研究成果報告2015―11月19日（木）　国立極地研究所１階交流アトリウ

Interannual variability of sea ice production in a hybrid latent and sensible heat coastal polynya off Barrow

第6回極域科学シンポジウム分野横断セッション：[IA] 急変する北極気候システム及びその全球的な影響の総合的解明―GRENE北極気候変動研究事業研究成果報告2015―11月19日（木）　国立極地研究所１階交流アトリウ

A negative phase shift of the winter AO/NAO due to the recent Arctic sea-ice reduction in late autumn

This paper examines the possible linkage between the recent reduction in Arctic sea-ice extent and the wintertime Arctic Oscillation (AO)/North Atlantic Oscillation (NAO). Observational analyses using the ERA interim reanalysis and merged Hadley/Optimum Interpolation Sea Surface Temperature data reveal that a reduced (increased) sea-ice area in November leads to more negative (positive) phases of the AO and NAO in early and late winter, respectively. We simulate the atmospheric response to observed sea-ice anomalies using a high-top atmospheric general circulation model (AGCM for Earth Simulator, AFES version 4.1). The results from the simulation reveal that the recent Arctic sea-ice reduction results in cold winters in mid-latitude continental regions, which are linked to an anomalous circulation pattern similar to the negative phase of AO/NAO with an increased frequency of large negative AO events by a factor of over two. Associated with this negative AO/NAO phase, cold air advection from the Arctic to the mid-latitudes increases. We found that the stationary Rossby wave response to the sea-ice reduction in the Barents Sea region induces this anomalous circulation. We also found a positive feedback mechanism resulting from the anomalous meridional circulation that cools the mid-latitudes and warms the Arctic, which adds an extra heating to the Arctic air column equivalent to about 60% of the direct surface heat release from the sea-ice reduction. The results from this high-top model experiment also suggested a critical role of the stratosphere in deepening the tropospheric annular mode and modulation of the NAO in mid to late winter through stratosphere-troposphere coupling

The stratospheric pathway for Arctic impacts on midlatitude climate

Recent evidence from both observations and model simulations suggests that an Arctic sea ice reduction tends to cause a negative Arctic Oscillation (AO) phase with severe winter weather in the Northern Hemisphere, which is often preceded by weakening of the stratospheric polar vortex. Although this evidence hints at a stratospheric involvement in the Arctic-midlatitude climate linkage, the exact role of the stratosphere remains elusive. Here we show that tropospheric AO response to the Arctic sea ice reduction largely disappears when suppressing the stratospheric wave mean flow interactions in numerical experiments. The results confirm a crucial role of the stratosphere in the sea ice impacts on the midlatitudes by coupling between the stratospheric polar vortex and planetary-scale waves. Those results and consistency with observation-based evidence suggest that a recent Arctic sea ice loss is linked to midlatitudes extreme weather events associated with the negative AO phase

Sea-ice thickness in the coastal northeastern Chukchi Sea from moored ice-profiling sonar

Time series ice-draft data were obtained from moored ice-profiling sonar (IPS), in the coastal northeastern Chukchi Sea during 2009/10. Time series data show seasonal growth of sea-ice draft, occasionally interrupted by coastal polynya. The sea-ice draft distribution indicates a slightly lower abundance of thick, deformed ice compared with the eastern Beaufort Sea. In January, a rapid increase in the abundance of thick ice coincided with a period of minimal drift indicating compaction again the coast and dynamical thickening. The overall mean draft and corresponding derived thickness are 1.27 and 1.38 m, respectively. The evolution of modal ice thickness observed can be explained mostly by thermodynamic growth. The derived ice thicknesses are used to estimate heat losses based on ERA-interim data. Heat losses from the raw, 1 s IPS data are ∼50 and 100% greater than those calculated using IPS data averaged over spatial scales of ∼20 and 100 km, respectively. This finding demonstrates the importance of subgrid-scale ice-thickness distribution for heat-loss calculation. The heat-loss estimate based on thin ice data derived from AMSR-E data corresponds well with that from the 1 s observed ice-thickness data, validating heat-loss estimates from the AMSR-E thin ice-thickness algorithm

Arctic polynya regions: Daily polynya area and ice production for 2002/2003 to 2017/2018

A precise knowledge of wintertime sea-ice production in Arctic polynyas is not only required to enhance our understanding of atmosphere - sea-ice - ocean interactions, but also to verify frequently utilized climate and ocean models. In this study, a high-resolution (2km) MODIS thermal infrared satellite data set featuring spatial and temporal characteristics of 17 Arctic polynya regions (see attached overview map) for the winter seasons 2002/2003 to 2017/2018 is directly compared to a similar data set based on AMSR-E passive microwave data (available for 2002/2003 to 2010/2011). The MODIS data set is purely based on a 1D energy balance model, where thin-ice thicknesses (up to 20cm) are directly derived from ice-surface temperature swath data and ERA-Interim atmospheric reanalysis data on a quasi-daily basis. A gap-filling approach is applied to account for cloud and data gaps in the MODIS composites. Estimation of the thin-ice thickness in the AMSR-E data set is based on an empirical approach that utilizes a distinct polarization ratio (PR) - ice thickness relationship. More detailed information on the retrieval of the data can be found in the referenced publication

Estimation of Sea Ice Production in the Bering Sea From AMSR-E and AMSR2 Data, With Special Emphasis on the Anadyr Polynya

We created, for the first time, a map of sea ice production in the Bering Sea, based on thin-ice thickness data from the Advanced Microwave Scanning Radiometers (AMSR-E and AMSR2) with a heat flux calculation. We used the AMSR-E thin-ice algorithm developed for the Arctic Ocean with some modification. We provided a 16-yr data set of ice production from the 2002/2003 to 2018/2019 seasons, excepting the 2011/2012 season. It is found that the Anadyr polynya has by far the highest sea ice production (average of 93 km(3)/yr) and accounts for more than 30% of all polynya ice production in the Bering Sea. The combined ice production in the Anadyr, Anadyr Strait, and St. Lawrence polynyas becomes the second-largest ice production during the AMSR-E period in the Northern Hemisphere. It is considered that the high ice production in the Anadyr polynya produces cold, saline, nutrient-rich water, so-called Anadyr Water, which would contribute to the formation of the cold halocline layer and high biological productivity. The ice production in the Anadyr polynya shows very large year-to-year variability. The record low ice extent year of the 2017/2018 season is also the lowest ice production year; the production is only one tenth of the highest value, observed during the 2015/2016 season. The high sensitivity of the wind direction and strength to the location of the Aleutian Low causes this large variability. We also built reconstruction schemes of ice production in the polynyas, using the offshore wind and air temperature, by multiple linear regression