scholarly journals Recent changes in pan-Antarctic surface snowmelt detected by AMSR-E and AMSR2

2019 ◽  
Author(s):  
Lei Zheng ◽  
Chunxia Zhou ◽  
Tingjun Zhang ◽  
Qi Liang ◽  
Kang Wang
Keyword(s):  
Sea Ice ◽  
Ice Sheet ◽  
Remote Sensing Data ◽  
Microwave Remote Sensing ◽  
Southern Annular Mode ◽  
Temporal Variations ◽  
Acquisition Time ◽  
Polar Regions ◽  
Antarctic Sea Ice ◽  
The Antarctic

Abstract. Surface snowmelt in the pan-Antarctic, including the Antarctic sea ice and ice sheet, is crucial to the mass and energy balance in polar regions and can serve as an indicator of climate change. We investigated the spatial and temporal variations of the surface snowmelt over the entire pan-Antarctic as a whole from 2002 to 2017 by using the passive microwave remote sensing data. The stable orbit and appropriate acquisition time of the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) and the Advanced Microwave Scanning Radiometer 2 (AMSR2) enable us to take full advantage of the daily brightness temperature (Tb) variations to detect the surface snowmelt events. In this study, diurnal amplitude variations of AMSR-E/2 vertically polarized 36.5 GHz Tb (DAV36V) were utilized to map the pan-Antarctic snowmelt because it is unaffected by the snow metamorphism. We validated the DAV36V method against the ground-based measurements and further improved the method over the marginal sea ice zone by excluding the effect of open water. Snowmelt detected by AMSR-E/2 data agreed well with that derived by ERA-Interim reanalysis, and much more extensive than that detected by the Special Sensor Microwave/Imager (SSM/I) data. On average, pan-Antarctic snowmelt began on 19 September, and experienced 32 melt events. Annual mean melt extent on the Antarctic ice sheet (AIS) was only 9 % of that on the Antarctic sea ice. Overall, the pan-Antarctic surface snowmelt showed a trend (at 95 % confidence level) toward later melt onset (0.70 days yr−1) during the 2002–2017 period. Surface snowmelt was well correlated with atmospheric indices in some regions. Notably, the decreasing surface snowmelt on the AIS was very likely linked with the enhancing summer Southern Annular Mode.

scholarly journals Recent changes in pan-Antarctic region surface snowmelt detected by AMSR-E and AMSR2

2020 ◽  
Vol 14 (11) ◽  
pp. 3811-3827
Author(s):  
Lei Zheng ◽  
Chunxia Zhou ◽  
Tingjun Zhang ◽  
Qi Liang ◽  
Kang Wang
Keyword(s):  
Sea Ice ◽  
Remote Sensing Data ◽  
Microwave Remote Sensing ◽  
Open Water ◽  
Southern Annular Mode ◽  
Temporal Variations ◽  
Polar Regions ◽  
Antarctic Region ◽  
Marginal Sea ◽  
The Antarctic

Abstract. Surface snowmelt in the pan-Antarctic region, including the Antarctic ice sheet (AIS) and sea ice, is crucial to the mass and energy balance in polar regions and can serve as an indicator of climate change. In this study, we investigate the spatial and temporal variations in surface snowmelt over the entire pan-Antarctic region from 2002 to 2017 by using passive microwave remote sensing data. The stable orbits and appropriate acquisition times of the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) and the Advanced Microwave Scanning Radiometer 2 (AMSR2) enable us to take full advantage of daily brightness temperature (Tb) variations to detect surface snowmelt. The difference between AMSR-E/2 ascending and descending 36.5 GHz Tb values in vertical polarization (DAV36) was utilized to map the pan-Antarctic region snowmelt, as this method is unaffected by snow metamorphism. We evaluated the DAV36 algorithm against ground-based measurements and further improved the method over the marginal sea ice zone by excluding the effect of open water. Snowmelt detected by AMSR-E/2 data was more extensive and persistent than that detected by the Special Sensor Microwave/Imager (SSM/I) data. Continuous melt onset (CMO) ranged from August in the marginal sea ice zone to January in the Antarctic inland, and the early transient melt events occurred several days to more than 2 months earlier. The pan-Antarctic region CMO was significantly correlated (R=0.54, p<0.05) with the summer Southern Annular Mode (SAM). The decreased AIS melt extent was very likely linked (R=-0.82, p<0.01) with the enhanced summer SAM.

Investigating the impact of the Southern Annular Mode on ice-shelf basal melt in Antarctica using a regional ocean model forced by reanalysis data

2021 ◽  
Author(s):  
Deborah Verfaillie ◽  
Charles Pelletier ◽  
Hugues Goosse ◽  
Nicolas Jourdain ◽  
Vincent Favier ◽  
...  
Keyword(s):  
Sea Ice ◽  
Ice Sheet ◽  
Southern Annular Mode ◽  
Polar Regions ◽  
High Latitudes ◽  
Ice Shelf ◽  
Sea Level Pressure ◽  
The Past ◽  
The Antarctic ◽  
The Impact

&lt;p&gt;The climate of polar regions is characterized by large fluctuations and has experienced dramatic changes over the past decades. In the high latitudes of the Southern Hemisphere, the patterns of changes in sea ice and ice sheet mass, in particular, are more complex than for the Northern Hemisphere. Some regions have warmed less than the global average with some sea-ice advance, in particular in the Ross Sea, while other regions such as the Bellingshausen Sea have warmed significantly and displayed sea-ice loss. The Antarctic Ice Sheet has also lost mass in the past decades, with a spectacular thinning and weakening of ice shelves, i.e., the floating extensions of the grounded ice sheet. Despite recent advances in observing and modelling the Antarctic climate, the mechanisms at the origin of those trends are very uncertain because of the limited amount of observations and the large biases of climate models in polar regions, in concert with the large internal variability prevailing in the Antarctic. One of the most important atmospheric modes of climate variability in the Southern Ocean is the Southern Annular Mode (SAM), which represents the position and the strength of the westerly winds. During years with a positive SAM index, lower sea level pressure at high latitudes and higher sea level pressure at low latitudes occur, resulting in a stronger pressure gradient and intensified Westerlies. However, the current knowledge of the impact of these fluctuations of the Westerlies on the Southern Ocean and Antarctic cryosphere is still limited. Some efforts have been devoted over the past few years to the impact of the SAM on the Antarctic sea ice and the surface mass balance of the ice sheet from an atmospheric-specific perspective. Recently, a few studies have focused on the local impact on ice-shelf basal melt in specific regions of Antarctica. However, to our knowledge, there is no such study of the impact of the SAM on ice-shelf basal melt at the pan-Antarctic scale. In this communication, we will address this issue by using simulations performed with the regional ocean and sea-ice model NEMO-LIM3.6 at a spatial resolution of 0.25&amp;#176; forced by the ERA5 reanalysis over the period 1979-2018 CE. The impact of both the annular and the non-annular components of the SAM on ice-shelf basal melt will be assessed through regressions and correlations between the seasonal or annual averages of the SAM index and the ice-shelf basal melt.&lt;/p&gt;

scholarly journals Positive Trend in the Antarctic Sea Ice Cover and Associated Changes in Surface Temperature

2017 ◽  
Vol 30 (6) ◽  
pp. 2251-2267 ◽  
Author(s):  
Josefino C. Comiso ◽  
Robert A. Gersten ◽  
Larry V. Stock ◽  
John Turner ◽  
Gay J. Perez ◽  
...  
Keyword(s):  
Sea Ice ◽  
Surface Temperature ◽  
Climate Models ◽  
Ice Cover ◽  
Southern Annular Mode ◽  
Positive Trend ◽  
Growth Season ◽  
Sea Ice Extent ◽  
Antarctic Sea Ice ◽  
The Antarctic

Abstract The Antarctic sea ice extent has been slowly increasing contrary to expected trends due to global warming and results from coupled climate models. After a record high extent in 2012 the extent was even higher in 2014 when the magnitude exceeded 20 × 106 km2 for the first time during the satellite era. The positive trend is confirmed with newly reprocessed sea ice data that addressed inconsistency issues in the time series. The variability in sea ice extent and ice area was studied alongside surface ice temperature for the 34-yr period starting in 1981, and the results of the analysis show a strong correlation of −0.94 during the growth season and −0.86 during the melt season. The correlation coefficients are even stronger with a one-month lag in surface temperature at −0.96 during the growth season and −0.98 during the melt season, suggesting that the trend in sea ice cover is strongly influenced by the trend in surface temperature. The correlation with atmospheric circulation as represented by the southern annular mode (SAM) index appears to be relatively weak. A case study comparing the record high in 2014 with a relatively low ice extent in 2015 also shows strong sensitivity to changes in surface temperature. The results suggest that the positive trend is a consequence of the spatial variability of global trends in surface temperature and that the ability of current climate models to forecast sea ice trend can be improved through better performance in reproducing observed surface temperatures in the Antarctic region.

A comparison of Arctic and Antarctic climate change, present and future

2009 ◽  
Vol 21 (3) ◽  
pp. 179-188 ◽  
Author(s):  
John E. Walsh
Keyword(s):  
Sea Ice ◽  
Atmospheric Circulation ◽  
Low Frequency ◽  
Southern Annular Mode ◽  
The Arctic ◽  
Polar Regions ◽  
Apparent Paradox ◽  
Late 20Th Century ◽  
Model Simulations ◽  
The Antarctic

AbstractOngoing climate variations in the Arctic and Antarctic pose an apparent paradox. In contrast to the large warming and loss of sea ice in the Arctic in recent decades, Antarctic temperatures and sea ice show little change except for the Antarctic Peninsula. However, model simulations indicate that the Arctic changes have been shaped largely by low-frequency variations of the atmospheric circulation, superimposed on a greenhouse warming that is apparent in model simulations when ensemble averages smooth out the circulation-driven variability of the late 20th century. By contrast, the Antarctic changes of recent decades appear to be shaped by ozone depletion and an associated strengthening of the southern annular mode of the atmospheric circulation. While the signature of greenhouse-driven change is projected to emerge from the natural variability during the present century, the emergence of a statistically significant greenhouse signal may be slower than in other regions. Models suggest that feedbacks from retreating sea ice will make autumn and winter the seasons of the earliest emergence of the greenhouse signal in both Polar Regions. Priorities for enhanced robustness of the Antarctic climate simulations are the inclusion of ozone chemistry and the realistic simulation of water vapour over the Antarctic Ice Sheet.

scholarly journals Antarctic sea ice types from active and passive microwave remote sensing

2022 ◽  
Author(s):  
Christian Melsheimer ◽  
Gunnar Spreen ◽  
Yufang Ye ◽  
Mohammed Shokr
Keyword(s):  
Time Series ◽  
Sea Ice ◽  
Microwave Remote Sensing ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Distribution Data ◽  
Synthetic Aperture Radar Data ◽  
Current Time ◽  
Antarctic Sea Ice ◽  
The Antarctic

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.

scholarly journals Brief communication: Spatial and temporal variations in surface snow chemistry along a traverse from coastal East Antarctica to the ice sheet summit (Dome A)

2021 ◽  
Vol 15 (2) ◽  
pp. 1087-1095
Author(s):  
Guitao Shi ◽  
Hongmei Ma ◽  
Zhengyi Hu ◽  
Zhenlou Chen ◽  
Chunlei An ◽  
...  
Keyword(s):  
Sea Ice ◽  
Ice Sheet ◽  
Temporal Variations ◽  
Sea Salt ◽  
Biogenic Emissions ◽  
Dome A ◽  
Sea Salts ◽  
Snow Chemistry ◽  
Surface Snow ◽  
The Antarctic

Abstract. To better understand snow chemistry in different environments across the Antarctic ice sheet, we investigated snow ions on a traverse from the coast to Dome A. Results show that the non-sea-salt (nss) fractions of K+, Mg2+, and Ca2+ are mainly from terrestrial particle mass and nssCl− is associated with HCl. Spatially, the non-sea-salt fractions of ions to the totals are higher in the interior areas than on the coast, and seasonally, the proportions are higher in summer than in winter. Negative nssSO42- on the coast indicates sea salts from the sea ice, and marine biogenic emissions dominate snow SO42- in interior areas throughout the year.

scholarly journals Ice–Atmosphere Feedbacks Dominate the Response of the Climate System to Drake Passage Closure

2017 ◽  
Vol 30 (15) ◽  
pp. 5775-5790 ◽  
Author(s):  
Matthew H. England ◽  
David K. Hutchinson ◽  
Agus Santoso ◽  
Willem P. Sijp
Keyword(s):  
Sea Ice ◽  
Heat Transport ◽  
Southern Hemisphere ◽  
Ice Sheet ◽  
Drake Passage ◽  
Climate System ◽  
Albedo Feedback ◽  
Antarctic Sea Ice ◽  
Ocean Atmosphere ◽  
The Antarctic

The response of the global climate system to Drake Passage (DP) closure is examined using a fully coupled ocean–atmosphere–ice model. Unlike most previous studies, a full three-dimensional atmospheric general circulation model is included with a complete hydrological cycle and a freely evolving wind field, as well as a coupled dynamic–thermodynamic sea ice module. Upon DP closure the initial response is found to be consistent with previous ocean-only and intermediate-complexity climate model studies, with an expansion and invigoration of the Antarctic meridional overturning, along with a slowdown in North Atlantic Deep Water (NADW) production. This results in a dominance of Southern Ocean poleward geostrophic flow and Antarctic sinking when DP is closed. However, within just a decade of DP closure, the increased southward heat transport has melted back a substantial fraction of Antarctic sea ice. At the same time the polar oceans warm by 4°–6°C on the zonal mean, and the maximum strength of the Southern Hemisphere westerlies weakens by ≃10%. These effects, not captured in models without ice and atmosphere feedbacks, combine to force Antarctic Bottom Water (AABW) to warm and freshen, to the point that this water mass becomes less dense than NADW. This leads to a marked contraction of the Antarctic overturning, allowing NADW to ventilate the abyssal ocean once more. Poleward heat transport settles back to very similar values as seen in the unperturbed DP open case. Yet remarkably, the equilibrium climate in the closed DP configuration retains a strong Southern Hemisphere warming, similar to past studies with no dynamic atmosphere. However, here it is ocean–atmosphere–ice feedbacks, primarily the ice-albedo feedback and partly the weakened midlatitude jet, not a vigorous southern sinking, which maintain the warm polar oceans. This demonstrates that DP closure can drive a hemisphere-scale warming with polar amplification, without the presence of any vigorous Southern Hemisphere overturning circulation. Indeed, DP closure leads to warming that is sufficient over the West Antarctic Ice Sheet region to inhibit ice-sheet growth. This highlights the importance of the DP gap, Antarctic sea ice, and the associated ice-albedo feedback in maintaining the present-day glacial state over Antarctica.

Passive microwave images of the polar regions and research applications

Polar Record ◽  
1977 ◽  
Vol 18 (116) ◽  
pp. 431-450 ◽  
Author(s):  
H. Jay Zwally ◽  
Per Gloersen
Keyword(s):  
Sea Ice ◽  
Microwave Radiometer ◽  
Ice Sheet ◽  
Passive Microwave ◽  
Microwave Emission ◽  
Polar Regions ◽  
Yield Information ◽  
Potential Applications ◽  
Microwave Radiometers ◽  
The Antarctic

Passive microwave images of the polar regions, first produced after the launch of the Nimbus-5 Electrically Scanning Microwave Radiometer (ESMR)in December 1972, have become a valuable new source of polar information. Some of the potential applications of this new capability were anticipated. Of these, the sensing of sea ice through clouds and the polar night is probably the most important application for polar research and for operations on the polar seas. Other applications, such as the measurement of certain near-surfaceice sheet parameters, have been formulated more recently. Measurement of various ocean surface parameters is expected from the forthcoming multifrequency microwave observations. Undoubtedly additional uses of passive microwave datawill be conceived and developed. Two remarkable aspects of satellite-borne microwave radiometers are the complete spatial detail obtained by the scanning sensors and the temporal detail provided by continual coverage. For example, the observations of detailed microwave emission patterns over the Antarctic ice sheet should yield information that could not be obtained by surface or even aircraft measurements. Sequences of images produced at three-day intervalsreveal short-term ice sheet and sea ice phenomena that would otherwise be missed.

Impact of ice sheet – ocean interactions on the Southern Ocean using fully coupled models over a circumpolar domain

2021 ◽  
Author(s):  
Charles Pelletier ◽  
Lars Zipf ◽  
Konstanze Haubner ◽  
Deborah Verfaillie ◽  
Hugues Goosse ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Ice Sheet ◽  
The Arctic ◽  
Surface Cooling ◽  
Coupled Models ◽  
Sea Ice Extent ◽  
Antarctic Ice Sheet ◽  
Antarctic Sea Ice ◽  
The Antarctic

&lt;p&gt;From at least 1979 up until 2016, the surface of the Southern Ocean cooled down, leading to a small Antarctic sea ice extent increase, which is in stark contrast with the Arctic Ocean. The attribution of the origin of these robust observations is still very uncertain. Among other phenomena, the direct, two-way interactions between the Southern Ocean and the Antarctic ice sheet, through basal melting of its numerous and large ice-shelf cavities, have been suggested as a potentially important contributor of this cooling. In order to address this question, we perform multidecadal coupled ice sheet &amp;#8211; ocean numerical simulations relying on f.ETISh-v1.7 and NEMO3.6-LIM3 for simulating the Antarctic ice sheet and Southern Ocean (including sea ice), respectively. This presentation is twofold. First, we present the technical aspects of the coupling infrastructure (e.g. workflow and exchanged information in between models). Second, we investigate the ice sheet &amp;#8211; ocean feedbacks on the Southern Ocean, their interactions, and the roles of the related physical mechanisms on the ocean surface cooling.&lt;/p&gt;

scholarly journals The Year of Polar Prediction in the Southern Hemisphere (YOPP-SH)

2020 ◽  
Vol 101 (10) ◽  
pp. E1653-E1676 ◽  
Author(s):  
David H. Bromwich ◽  
Kirstin Werner ◽  
Barbara Casati ◽  
Jordan G. Powers ◽  
Irina V. Gorodetskaya ◽  
...  
Keyword(s):  
Sea Ice ◽  
Southern Hemisphere ◽  
Warm Season ◽  
Cold Season ◽  
Polar Regions ◽  
Antarctic Sea Ice ◽  
Early Results ◽  
Operational Activity ◽  
The Antarctic ◽  
Education Outreach

AbstractThe Year of Polar Prediction in the Southern Hemisphere (YOPP-SH) had a special observing period (SOP) that ran from 16 November 2018 to 15 February 2019, a period chosen to span the austral warm season months of greatest operational activity in the Antarctic. Some 2,200 additional radiosondes were launched during the 3-month SOP, roughly doubling the routine program, and the network of drifting buoys in the Southern Ocean was enhanced. An evaluation of global model forecasts during the SOP and using its data has confirmed that extratropical Southern Hemisphere forecast skill lags behind that in the Northern Hemisphere with the contrast being greatest between the southern and northern polar regions. Reflecting the application of the SOP data, early results from observing system experiments show that the additional radiosondes yield the greatest forecast improvement for deep cyclones near the Antarctic coast. The SOP data have been applied to provide insights on an atmospheric river event during the YOPP-SH SOP that presented a challenging forecast and that impacted southern South America and the Antarctic Peninsula. YOPP-SH data have also been applied in determinations that seasonal predictions by coupled atmosphere–ocean–sea ice models struggle to capture the spatial and temporal characteristics of the Antarctic sea ice minimum. Education, outreach, and communication activities have supported the YOPP-SH SOP efforts. Based on the success of this Antarctic summer YOPP-SH SOP, a winter YOPP-SH SOP is being organized to support explorations of Antarctic atmospheric predictability in the austral cold season when the southern sea ice cover is rapidly expanding.

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