Antarctic sea ice types from active and passive microwave remote sensing

Abstract

Abstract. Polar sea ice is one of the Earth’s climate components that has been significantly affected by the recent trend of global warming. While the sea ice area in the Arctic has been decreasing at a rate of about 4 % per decade, the multi-year ice (MYI), also called perennial ice, is decreasing at a faster rate of 10 %–15 % per decade. On the other hand, the sea ice area in the Antarctic region was slowly increasing at a rate of about 1.5 % per decade until 2014 and since then it has fluctuated without a clear trend. However, no data about ice type areas are available from that region, particularly of MYI. Due to differences in physical and crystalline structural properties of sea ice and snow between the two polar regions, it has become difficult to identify ice types in the Antarctic. Until recently, no method has existed to monitor the distribution and temporal development of Antarctic ice types, particularly MYI throughout the freezing season and on decadal time scales. In this study, we have adapted a method for retrieving Arctic sea ice types and partial concentrations using microwave satellite observations to fit the Antarctic sea ice conditions. The first circumpolar, long-term time series of Antarctic sea ice types; MYI, first-year ice and young ice is being established, so far covering years 2013–2019. Qualitative comparison with synthetic aperture radar data, with charts of the development stage of the sea ice, and with Antarctic polynya distribution data show that the retrieved ice types, in particular the MYI, are reasonable. Although there are still some shortcomings, the new retrieval for the first time allows insight into the evolution and dynamics of Antarctic sea ice types. The current time series can in principle be extended backwards to start in the year 2002 and can be continued with current and future sensors.

New estimates of the pan-Arctic sea ice–atmosphere neutral drag coefficients from ICESat-2 elevation data

“…In addition to pan-Arctic averages, we also produce these statistics for multiyear ice (MYI) and first-year ice (FYI). Here, we make use of the MYI concentration retrieved using brightness temperatures from the microwave radiometer AMSR2 and radar backscatter from the C-band scatterometer ASCAT (Shokr et al, 2008;Ye et al, 2016a, b;Melsheimer et al, 2022). Sea ice area classified as below 50% MYI according to the retrieval, are considered as FYI and used to compute FYI averages and conversely all values equal to and above 50% are used to compute MYI averages.…”

A Comparison of Top‐Of‐Atmosphere Radiative Fluxes From CERES and ARISE

“…Cloud properties are produced using MODIS and VIIRS data by the CERES Cloud Working Group (Minnis et al., 2020; Trepte et al., 2019). Surface type is determined by the ASI AMSR2 SIC (Melsheimer & Spreen, 2019; Spreen et al., 2008) dataset—a high spatial (3.125 km) and temporal resolution passive microwave derived data set.…”

Sea Ice Remote Sensing—Recent Developments in Methods and Climate Data Sets

“…A recent development is to merge microwave radiometer and scatterometer data to improve the discrimination between firstyear and multiyear ice (e.g. Ye et al 2016;Melsheimer et al 2022). Both radiometer and scatterometer data can provide ice type fractions at spatial resolutions of 10 km and lower.…”

“…Fig.2The Antarctic on 1 April 2020 observed by satellite microwave radiometers. Left: Sea ice concentration (ASI) from AMSR2(Spreen et al 2008); Middle: Multiyear ice fraction from combined AMSR2 and ASCAT(Melsheimer et al 2022); Right: Thickness of thin sea ice from merged SMAP and SMOS(Patilea et al 2019;Mchedlishvili et al 2022) …”