Regions of rapid sea ice change: An inter-hemispheric seasonal comparison (original) (raw)
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Consistent Changes in the Sea Ice Seasonal Cycle in Response to Global Warming
Journal of Climate, 2011
The Northern Hemisphere sea ice cover has diminished rapidly in recent years and is projected to continue to diminish in the future. The year-to-year retreat of Northern Hemisphere sea ice extent is faster in summer than winter, which has been identified as one of the most striking features of satellite observations as well as of state-of-the-art climate model projections. This is typically understood to imply that the sea ice cover is most sensitive to climate forcing in summertime, and previous studies have explained this by calling on factors such as the surface albedo feedback. In the Southern Hemisphere, however, it is the wintertime sea ice extent that retreats fastest in climate model projections. Here, it is shown that the interhemispheric differences in the model projections can be attributed to differences in coastline geometry, which constrain where sea ice can occur. After accounting for coastline geometry, it is found that the sea ice changes simulated in both hemispheres in most climate models are consistent with sea ice retreat being fastest in winter in the absence of landmasses. These results demonstrate that, despite the widely differing rates of ice retreat among climate model projections, the seasonal structure of the sea ice retreat is robust among the models and is uniform in both hemispheres.
Possible connections of the opposite trends in Arctic and Antarctic sea-ice cover
Scientific reports, 2017
Sea ice is an important component of the global climate system and a key indicator of climate change. A decreasing trend in Arctic sea-ice concentration is evident in recent years, whereas Antarctic sea-ice concentration exhibits a generally increasing trend. Various studies have investigated the underlying causes of the observed trends for each region, but possible linkages between the regional trends have not been studied. Here, we hypothesize that the opposite trends in Arctic and Antarctic sea-ice concentration may be linked, at least partially, through interdecadal variability of the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). Although evaluation of this hypothesis is constrained by the limitations of the sea-ice cover record, preliminary statistical analyses of one short-term and two long-term time series of observed and reanalysis sea-ice concentrations data suggest the possibility of the hypothesized linkages. For all three data sets, t...
Relationship of the Extent of Antarctic and Arctic Ice with Temperature Changes, 1979–2020
Doklady Earth Sciences
Quantitative estimates of the relationship between interannual variations in the extent of Antarctic and Arctic sea ice and changes in the surface air temperature in the Northern and Southern hemispheres are obtained using satellite, ground-based, and reanalysis data for the past four decades (1980–2019). It is shown that the previously noted general increase in the extent of Antarctic sea ice observed until recent years from satellite data (available only since the late 1970s) over the background global warming and a rapid decrease in the extent of Arctic sea ice is associated with a regional decrease in the surface temperature at Antarctic latitudes from the end of the 1970s. This is a result of regional manifestation of natural climate variations with periods of up to several decades against the background of global secular warming with a relatively weak temperature trend over the ocean in the Southern Hemisphere. Since 2016, a sharp decrease in the extent of Antarctic sea ice in...
Spatial distribution of trends and seasonally in the hemispheric sea ice covers: 1978 – 1996
Journal of Geophysical Research, 1999
We extend earlier analyses of a 8.8-year sea ice data set that described the local seasonal variations and trends in each of the hemispheric sea ice covers to the recently merged 18.2-year sea ice record from four satellite instruments. The seasonal cycle characteristics remain essentially the same as for the shorter time series, but the local trends are markedly different, in some cases reversing sign. The sign reversal reflects the lack of a consistent long-term trend and could be the result of localized long-term oscillations in the hemispheric sea ice covers. By combining the separate hemispheric sea ice records into a global one, we have shown that there are statistically significant net decreases in the sea ice coverage on a global scale. The change in the global sea ice extent is -0.01 + 0.003 x 106 km2 per decade. The decrease in the areal coverage of the sea ice is only slightly smaller, so that the difference in the two, the ice-free areas within the packs, has no statistically significant change. 20,827
The Arctic and Antarctic Sea-Ice Area Index Records versus Measured and Modeled Temperature Data
Advances in Meteorology, 2015
Here we study the Arctic and Antarctic sea-ice area records provided by the National Snow and Ice Data Center (NSIDC). These records reveal an opposite climatic behavior: since 1978 the Arctic sea-ice area index decreased, that is, the region has warmed, while the Antarctic sea-ice area index increased, that is, the region has cooled. During the last 7 years the Arctic sea-ice area has stabilized while the Antarctic sea-ice area has increased at a rate significantly higher than during the previous decades; that is, the sea-ice area of both regions has experienced a positive acceleration. This result is quite robust because it is confirmed by alternative temperature climate indices of the same regions. We also found that a significant 4-5-year natural oscillation characterizes the climate of these sea-ice polar areas. On the contrary, we found that the CMIP5 general circulation models have predicted significant warming in both polar sea regions and failed to reproduce the strong 4-5-...
Evaluating Impacts of Recent Arctic Sea Ice Loss on the Northern Hemisphere Winter Climate Change
Geophysical Research Letters, 2018
Wide disagreement among individual modeling studies has contributed to a debate on the role of recent sea ice loss in the Arctic amplification of global warming and the Siberian wintertime cooling trend. We perform coordinated experiments with six atmospheric general circulation models forced by the observed and climatological daily sea ice concentration and sea surface temperature. The results indicate that the impact of the recent sea ice decline is rather limited to the high-latitude lower troposphere in winter, and the sea ice changes do not significantly lead to colder winters over Siberia. The observed wintertime Siberian temperature and corresponding circulation trends are reproduced in a small number of ensemble members but not by the multimodel ensemble mean, suggesting that atmospheric internal dynamics could have played a major role in the observed trends. Plain Language Summary Understanding the mechanism governing the ongoing global warming is a major challenge facing our society and its sustainable growth. Together with the CO 2-forced warming, the concurrent polar sea ice loss might also have contributed to the observed Arctic warming amplification and also to the cooling trends over Eurasia through a dynamical teleconnection. However, previous individual modeling studies suggest widely different findings on the role of sea ice loss in Northern Hemisphere climate change. To help resolve this controversy, we used satellite-derived sea ice and sea-surface temperature to run coordinated hindcast experiments with five different atmospheric general circulation models. The multimodel ensemble-mean results presented in the paper reduce biases of each model and eliminate atmospheric internal unforced variability, and thus provide the best estimate to date of the signal of the polar sea ice loss. The results suggest that the impact of sea ice seems critical for the Arctic surface temperature changes, but the temperature trends elsewhere seem rather due to either sea-surface temperature changes or atmospheric internal variability. They give clear guidance on how to provide society with more accurate climate change attributions. Our work is of interest to stakeholders of countries in the Northern Hemisphere middle and high latitudes.
TRENDS IN POLAR SEA ICE EXTENT 1979-2015
A survey of trends in dispersed and concentrated sea ice extent in the Arctic in the northern summer and northern winter and in the Antarctic in the southern summer and southern winter for the period 1979-2015 shows a negative trend in dispersed and concentrated sea ice extent in the Arctic in the northern summer amid rising surface temperature in the northern hemisphere. The trend in concentrated sea ice extent in the Arctic summer is not uniform across the study period but mostly a phenomenon of the latter half from 1998-2014. A positive trend for dispersed sea ice extent in the Antarctic in winter amid rising winter temperature in the southern hemisphere is not matched by trends in concentrated sea ice extent and the degree of dispersion and is discounted as spurious. In the southern summer, we found no trends in sea ice extent in the Antarctic and no trend in mean surface temperature in the southern hemisphere. This work concerns only sea ice extent without considerations of the age, thickness, and total volume of sea ice. (Full text was revised on 4/25/2015)
Springtime atmospheric energy transport and the control of Arctic summer sea-ice extent
2013
The summer sea-ice extent in the Arctic has decreased in recent decades, a feature that has become one of the most distinct signals of the continuing climate change 1-4. However, the interannual variability is large-the ice extent by the end of the summer varies by several million square kilometres from year to year 5. The underlying processes driving this year-to-year variability are not well understood. Here we demonstrate that the greenhouse effect associated with clouds and water vapour in spring is crucial for the development of the sea ice during the subsequent months. In years where the end-of-summer sea-ice extent is well below normal, a significantly enhanced transport of humid air is evident during spring into the region where the ice retreat is encountered. This enhanced transport of humid air leads to an anomalous convergence of humidity, and to an increase of the cloudiness. The increase of the cloudiness and humidity results in an enhancement of the greenhouse effect. As a result, downward long-wave radiation at the surface is larger than usual in spring, which enhances the ice melt. In addition, the increase of clouds causes an increase of the reflection of incoming solar radiation. This leads to the counterintuitive effect: for years with little sea ice in September, the downwelling shortwave radiation at the surface is smaller than usual. That is, the downwelling shortwave radiation is not responsible for the initiation of the ice anomaly but acts as an amplifying feedback once the melt is started. The sea-ice extent in the Arctic has been steadily decreasing during the satellite remote-sensing era, 1979 to present (Fig. 1a). The highest rate of retreat is found in September 5 , which coincides with the month of the annual cycle that has the lowest ice extent. Factors that are believed to cause the ice retreat are, among others: changes in surface air temperature 6-8 , ice circulation in response to winds/pressure patterns 7-11 , and ocean currents 8 , as well as changes in radiative fluxes (for example, due to changes in cloud cover) 7,10,12-15 , and ocean conditions (for example, ocean warming 16). However, large interannual variability is superimposed onto the declining trend (Fig. 1a). The year-to-year deviation of the ice extent in September relative to the trend line varies by, on average, ±0.5 × 10 6 km 2 , but can reach 1.75 × 10 6 km 2 , which is around 25% of the mean September extent for 1979-2010. The magnitude of the variability shows considerable regional differences: a comparison of years with an anomalously large September sea-ice extent (HIYs-high ice years) with years showing an anomalously small ice extent (LIYs-low ice years) reveals that the variability is most pronounced in the Arctic Ocean north of Siberia (Fig. 1b,c). Significant ice-concentration anomalies of ∼±30% are observed for LIYs and HIYs in this area, which is chosen as the study area for the following analyses. In 2007 and 2012-the years showing the first and second lowest Arctic ice extent since the satellite observations began-a large part of this area became entirely ice free 17-19 .
Journal of Geophysical Research, 2008
Previous studies have shown strong contrasting trends in annual sea ice duration and in monthly sea ice concentration in two regions of the Southern Ocean: decreases in the western Antarctic Peninsula/southern Bellingshausen Sea (wAP/sBS) region and increases in the western Ross Sea (wRS) region. To better understand the evolution of these regional sea ice trends, we utilize the full temporal (quasi-daily) resolution of satellite-derived sea ice data to track spatially the annual ice edge advance and retreat from 1979 to 2004. These newly analyzed data reveal that sea ice is retreating 31 ± 10 days earlier and advancing 54 ± 9 days later in the wAP/sBS region (i.e., total change over 1979-2004), whereas in the wRS region, sea ice is retreating 29 ± 6 days later and advancing 31 ± 6 days earlier. Changes in the wAP/sBS and wRS regions, particularly as observed during sea ice advance, occurred in association with decadal changes in the mean state of the Southern Annular Mode (SAM; negative in the 1980s and positive in the 1990s) and the high-latitude response to El Niño-Southern Oscillation (ENSO). In general, the high-latitude ice-atmosphere response to ENSO was strongest when-SAM was coincident with El Niño and when +SAM was coincident with La Niña, particularly in the wAP/sBS region. In total, there were 7 of 11-SAMs between 1980 and 1990 and the 7 of 10 +SAMs between 1991 and 2000 that were associated with consistent decadal sea ice changes in the wAP/sBS and wRS regions, respectively. Elsewhere, ENSO/SAMrelated sea ice changes were not as consistent over time (e.g., western Weddell, Amundsen, and eastern Ross Sea region), or variability in general was high (e.g., central/ eastern Weddell and along East Antarctica).
Deep Sea Research Part II: Topical Studies in Oceanography, 2008
The Antarctic Peninsula region is undergoing rapid change: a warming in winter of almost 6 1C since 1950, the loss of six ice shelves, the retreat of 87% of the marine glaciers, and decreases in winter sea-ice duration. Concurrently, there is evidence of ecosystem change along the western Antarctic Peninsula (wAP). Since the life histories of most polar marine species are synchronized with the seasonal cycle of sea ice, we assess how the seasonal sea-ice cycle is changing in the wAP region. Four new metrics of seasonal sea-ice variability were extracted from spatial maps of satellite derived daily sea-ice concentration: (a) day of advance, (b) day of retreat, (c) the total number of sea-ice days (between day of advance and retreat), and (d) the percent time sea-ice was present (or sea-ice persistence). The spatiotemporal variability describes distinct onto offshore and alongshore differences in ice-ocean marine habitats, characterized overall by a longer sea-ice season in coastal regions (6.8-7.9 months) versus a shorter sea-ice season over the shelf (4.1-5.3 months), with onto offshore differences increasing southto-north. Large perturbations in the seasonality of the marine habitat occur in association with ENSO and Southern Annular Mode (SAM) variability. The local atmospheric response to these climate modes is largely a strengthening of the meridional winds during spring-to-autumn, which in turn affect the timing of the sea-ice retreat and subsequent advance. These perturbations are embedded in overall trends towards a later sea-ice advance, earlier retreat and consequently shorter sea-ice season, the impacts of which are expected to affect ecosystem functionality in the wAP region. A suite of ocean-atmosphere-ice interactions are described that are consistent with the amplified warming in late autumn, early winter.