Antarctic sea ice passive microwave signatures during summer and autumn

2002 ◽  
Author(s):  
J.C. Comiso ◽  
S.F. Ackley
Keyword(s):  
Sea Ice ◽  
Passive Microwave ◽  
Antarctic Sea Ice ◽  
Microwave Signatures

scholarly journals Analysis Of Interannual Changes In Antarctic Sea-Ice Cover Using Passive Microwave Observations (Abstract only)

1982 ◽  
Vol 3 ◽  
pp. 350-350
Author(s):  
H.J. Zwally ◽  
J.C. Comiso ◽  
C.L. Parkinson ◽  
F.D. Carsey ◽  
W.J. Campbell ◽  
...  
Keyword(s):  
Sea Ice ◽  
Ross Sea ◽  
Open Water ◽  
Mean Value ◽  
Weddell Sea ◽  
Passive Microwave ◽  
Average Decrease ◽  
Antarctic Sea Ice ◽  
Ice Coverage ◽  
Ice Concentration

A quantitative comparison of seasonal and interannual Antarctic sea-ice coverage over the four years 1973-76 has been accomplished through the use of passive microwave imagery from the Nimbus-5 satellite. For the entire Southern Ocean both the total ice extent (area with ice concentration greater than 15%) and the actual ice area (the spatially-integrated ice concentration) have decreased over this period of 4 a, but not uniformly in all regions. From 1973 to 1976 the annual-mean value of total ice extent decreased from 13.8 × 106 km2 to 12.1 × 106 km2, yielding an average decrease of 4.0% a−1. The inter-annual difference is greatest during the spring, as the ice decays, with the decrease in the December-mean averaging 8.4% a−1, the largest of any month. The decrease in the November-mean averaged 4.5% a−1. The overall decrease was principally due to the consistent yearly decrease of ice In the Weddell Sea sector (60°W to 20°E). Other sectors show less consistency. For instance, the ice in the Ross Sea sector (130°W to 160°E) increased from 1973 to 1974 and then decreased from 1974 to 1976, and no consistent trend is apparent in the ice extent between 20°E and 160°E. The total ice extent in the Bellingshausen- Amundsen seas sector (60°W to 130°W) actually increased slightly from 1973 to 1976. The area of the open water within the ice pack behaved differently from the total ice area, Increasing each year from February to November but having no clear interannual trend. A detailed analysis of the passive microwave imagery for the Antarctic region is planned for publication in an atlas.

scholarly journals Antarctic summer sea ice concentration and extent: comparison of ODEN 2006 ship observations, satellite passive microwave and NIC sea ice charts

2008 ◽  
Vol 2 (4) ◽  
pp. 623-647 ◽  
Author(s):  
B. Ozsoy-Cicek ◽  
H. Xie ◽  
S. F. Ackley ◽  
K. Ye
Keyword(s):  
Sea Ice ◽  
Linear Trend ◽  
Passive Microwave ◽  
The Arctic ◽  
Poor Correlation ◽  
Sea Ice Concentration ◽  
Sea Ice Extent ◽  
Antarctic Sea Ice ◽  
Ice Concentration ◽  
Ice Edge

Abstract. Antarctic sea ice cover has shown a slight increase in overall observed ice extent as derived from satellite mapping from 1979 to 2008, contrary to the decline observed in the Arctic regions. Spatial and temporal variations of the Antarctic sea ice however remain a significant problem to monitor and understand, primarily due to the vastness and remoteness of the region. While satellite remote sensing has provided and has great future potential to monitor the variations and changes of sea ice, uncertainties remain unresolved. In this study, the National Ice Center (NIC) ice edge and the AMSR-E (Advanced Microwave Scanning Radiometer – Earth Observing System) ice extent are examined, while the ASPeCt (Antarctic Sea Ice Process and Climate) ship observations from the Oden expedition in December 2006 are used as ground truth to verify the two products during Antarctic summer. While there is a general linear trend between ASPeCt and AMSR-E ice concentration estimates, there is poor correlation (R2=0.41) and AMSR-E tends to underestimate the low ice concentrations. We also found that the NIC sea ice edge agrees well with ship observations, while the AMSR-E shows the ice edge further south, consistent with its poorer detection of low ice concentrations. The northward extent of the ice edge at the time of observation (NIC) had mean values varying from 38 km to 102 km greater on different days for the area as compared with the AMSR-E sea ice extent. For the circumpolar area as a whole in the December period examined, AMSR-E therefore underestimates the area inside the ice edge at this time by up to 14% or, 1.5 million km2 less area, compared to the NIC ice charts. These differences alone can account for more than half of the purported sea ice loss between the pre 1960s and the satellite era suggested earlier from comparative analysis of whale catch data with satellite derived data. Preliminary comparison of satellite scatterometer data suggests better resolution of low concentrations than passive microwave, and therefore better fidelity with ship observations and NIC charts of the area inside the ice edge during Antarctic summer.

scholarly journals Spatio-temporal variability and decadal trends of snowmelt processes on Antarctic sea ice observed by satellite scatterometers

2019 ◽  
Author(s):  
Stefanie Arndt ◽  
Christian Haas
Keyword(s):  
Time Series ◽  
Sea Ice ◽  
Weddell Sea ◽  
Passive Microwave ◽  
The Arctic ◽  
Signal Frequency ◽  
Onset Date ◽  
Sea Ice Extent ◽  
Antarctic Sea Ice ◽  
Perennial Ice

Abstract. The timing and intensity of snowmelt processes on sea ice are key drivers determining the seasonal sea-ice energy and mass budgets. In the Arctic, satellite passive microwave and radar observations have revealed a trend towards an earlier snowmelt onset during the last decades, which is an important aspect of Arctic amplification and sea ice decline. Around Antarctica, snowmelt on perennial ice is weak and very different than in the Arctic, with most snow surviving the summer. Here we compile time series of snowmelt-onset dates on seasonal and perennial Antarctic sea ice from 1992 to 2014/15 using active microwave observations from European Remote Sensing Satellite (ERS-1/2), Quick Scatterometer (QSCAT) and Advanced Scatterometer (ASCAT) radar scatterometers. We define two snowmelt transition stages: A weak backscatter rise indicating the initial warming and metamorphism of the snowpack (pre-melt), followed by a rapid backscatter rise indicating the onset of thaw-freeze cycles (snowmelt). Results show large interannual variability with an average pre-melt onset date of 29 November and melt onset of 10 December, respectively, on perennial ice, without any significant trends over the study period, consistent with the small trends of Antarctic sea ice extent. There was a latitudinal gradient from early snowmelt onsets in mid-November in the northern Weddell Sea to late (end-December) or even absent snowmelt conditions in the southern Weddell Sea. We show that QSCAT Ku-band (13.4 GHz signal frequency) derived pre-melt and snowmelt onset dates are earlier by 25 and 11 days, respectively, than ERS and ASCAT C-band (5.6 GHz) derived dates. This offset has been considered when constructing the time series. Snowmelt onset dates from passive microwave observations (37 GHz) are later by 13 and 5 days than those from the scatterometers, respectively. Based on these characteristic differences between melt onset dates observed by different microwave wavelengths, we developed a conceptual model which illustrates how the evolution of seasonal snow temperature profiles affects different microwave bands with different penetration depths. These suggest that future multi-frequency active/passive microwave satellite missions could be used to resolve melt processes throughout the vertical snow column.

scholarly journals Snow depth product over Antarctic sea ice from 2002 to 2020 using multisource passive microwave radiometers

2021 ◽  
Author(s):  
Xiaoyi Shen ◽  
Chang-Qing Ke ◽  
Haili Li
Keyword(s):  
Tibetan Plateau ◽  
Sea Ice ◽  
Snow Depth ◽  
Depth Estimation ◽  
Passive Microwave ◽  
Energy Budgets ◽  
Antarctic Sea Ice ◽  
Basin Scale ◽  
Daily Scale ◽  
Microwave Radiometers

Abstract. Snow over sea ice controls energy budgets and affects sea ice growth/melting, and thus has essential effects on the climate. Passive microwave radiometers can be used for basin-scale snow depth estimation at a daily scale; however, previously published methods applied to Antarctica clearly underestimated snow depth, limiting their further application. Here, we estimated snow depth using microwave radiometers and a newly constructed, robust method by incorporating lower frequencies, which have been available from AMSR-E and AMSR-2 since 2002. A regression analysis using 7 years of Operation IceBridge (OIB) airborne snow depth measurements showed that the gradient ratio (GR) calculated using brightness temperatures in vertically polarized 37 and 19 GHz, i.e., GR(37/7), was optimal for deriving Antarctic snow depth, with a correlation coefficient of −0.64. We hence derive new coefficients based on GR(37/7) to improve the current snow depth estimation from passive microwave radiometers. Comparing the new retrieval with in situ measurements from the Australian Antarctic Data Centre showed that this method outperformed the previously available method, with a mean difference of 5.64 cm and an RMSD of 13.79 cm, compared to values of −14.47 cm and 19.49 cm, respectively. A comparison to shipborne observations from Antarctic Sea Ice Processes and Climate indicated that in thin ice regions, the proposed method performed slightly better than the previous method (with RMSDs of 16.85 cm and 17.61 cm, respectively). Comparable performances during the growth and melting seasons suggest that the proposed method can still be used during the melting season. Gaussian error propagation found an average snow depth uncertainty of 3.81 cm, which accounted for 12 % of the estimated mean snow depth. We generated a complete snow depth product over Antarctic sea ice from 2002 to 2020 on a daily scale, and negative trends could be found in all sea sectors and seasons. This dataset (including both snow depth and snow depth uncertainty) can be downloaded from National Tibetan Plateau Data Center, Institute of Tibetan Plateau Research, Chinese Academy of Sciences at http://data.tpdc.ac.cn/en/disallow/61ea8177-7177-4507-aeeb-0c7b653d6fc3/ (Shen and Ke, 2021, DOI: 10.11888/Snow.tpdc.271653).

Passive microwave signatures of sea ice

1992 ◽  
pp. 47-71 ◽  
Author(s):  
Duane T. Eppler ◽  
L. Dennis Farmer ◽  
Alan W. Lohanick ◽  
Mark R. Anderson ◽  
Donald J. Cavalieri ◽  
...  
Keyword(s):  
Sea Ice ◽  
Passive Microwave ◽  
Microwave Signatures
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