Decrease In Sea Ice Area Research Articles

Arctic Sea Ice Variations in the First Half of the 20th Century: A New Reconstruction Based on Hydrometeorological Data

The shrinking Arctic sea-ice area (SIA) in recent decades is a striking manifestation of the ongoing climate change. Variations of the Arctic sea ice have been continuously observed by satellites since 1979, relatively well monitored since the 1950s, but are highly uncertain in the earlier period due to a lack of observations. Several reconstructions of the historical gridded sea-ice concentration (SIC) data were recently presented based on synthesized regional sea-ice observations or by applying a hybrid model–empirical approach. Here, we present an SIC reconstruction for the period 1901–2019 based on established co-variability between SIC and surface air temperature, sea surface temperature, and sea level pressure patterns. The reconstructed sea-ice data for March and September are compared to the frequently used HadISST1.1 and SIBT1850 datasets. Our reconstruction shows a large decrease in SIA from the 1920 to 1940 concurrent with the Early 20th Century Warming event in the Arctic. Such a negative SIA anomaly is absent in HadISST1.1 data. The amplitude of the SIA anomaly reaches about 0.8 mln km2 in March and 1.5 mln km2 in September. The anomaly is about three times stronger than that in the SIBT1850 dataset. The larger decrease in SIA in September is largely due to the stronger SIC reduction in the western sector of the Arctic Ocean in the 70°–80°N latitudinal zone. Our reconstruction provides gridded monthly data that can be used as boundary conditions for atmospheric reanalyses and model experiments to study the Arctic climate for the first half of the 20th century.

Early Freeze-Up over the Bering Sea Controlled by the Aleutian Low

Early freeze-up affects the local marine environment and ecosystem throughout the entire Bering Sea. However, the process governing early freeze-up, which is responsible for the most significant interannual variation in the December sea ice area (SIA), is not well understood. Here, we show that the SIA in December is modulated by the Aleutian low in November by altering poleward heat transport (PHT). The stronger the November PHT is, the lower the December SIA. The rise in heat transport across the Bering Strait in November is consistent with the decrease in SIA in December, with a correlation of −0.71, further validating the regulatory role of PHT. The Aleutian low anomaly controls the local wind field, further altering the sea surface temperature and PHT. The center of the anomalous low-pressure in the east (west) generates the northerly (southeasterly) anomaly over the northern Bering Sea, leading to acceleration (suppression) of seawater cooling and weakening (enhancement) of the PHT. It is also found that a strong northerly surface current has a greater influence on the later SIA than warm water temperature. Hence, atmospheric forcing causing changes in ocean forcing is imperative to understand early freeze-up.

Coastal retreat at Kharasaveyskoye gas and condensate field area, Kara Sea, Russia since 1970s

Changes in coastal retreat rates, both spatial and temporal, are considered at the area of Kharasaveyskoye gas and condensate field for the period before the exploration till now. In the study area, the presence of permafrost makes the erosional coasts vulnerable to rising temperatures. The increase in air temperatures contributes to the thawing of coastal sediments and their accelerated destruction. And a decrease in sea ice area potentially increases the wave fetch. The rapidly changing climate of the Arctic should influence the processes of destruction of frozen coasts. At West Yamal Peninsula near Cape Kharasavey the average coastal retreat rate is 1.1 m per year (1977-2016) for 7 km of coastline. Based on the analysis of multi-temporal aerial and space images, it has been established that the maximum retreat rates are typical of coastal segments composed of icy sediments. As for temporal variability, the maximum rate of destruction was observed in 1977-1988 (up to 6.5 m per year) immediately after the beginning of economic development of the territory. In this key site, human impact affects the rate of coastal destruction more than variations in hydrometeorological parameters.

Atmospheric influences on the anomalous 2016 Antarctic sea ice decay

Abstract. In contrast to the Arctic, where total sea ice extent (SIE) has been decreasing for the last three decades, Antarctic SIE has shown a small, but significant, increase during the same time period. However, in 2016, an unusually early onset of the melt season was observed; the maximum Antarctic SIE was already reached as early as August rather than the end of September, and was followed by a rapid decrease. The decay was particularly strong in November, when Antarctic SIE exhibited a negative anomaly (compared to the 1979–2015 average) of approximately 2 million km2. ECMWF Interim reanalysis data showed that the early onset of the melt and the rapid decrease in sea ice area (SIA) and SIE were associated with atmospheric flow patterns related to a positive zonal wave number three (ZW3) index, i.e., synoptic situations leading to strong meridional flow and anomalously strong southward heat advection in the regions of strongest sea ice decline. A persistently positive ZW3 index from May to August suggests that SIE decrease was preconditioned by SIA decrease. In particular, in the first third of November northerly flow conditions in the Weddell Sea and the Western Pacific triggered accelerated sea ice decay, which was continued in the following weeks due to positive feedback effects, leading to the unusually low November SIE. In 2016, the monthly mean Southern Annular Mode (SAM) index reached its second lowest November value since the beginning of the satellite observations. A better spatial and temporal coverage of reliable ice thickness data is needed to assess the change in ice mass rather than ice area.

Unprecedented springtime retreat of Antarctic sea ice in 2016

AbstractDuring austral spring 2016 Antarctic sea ice extent (SIE) decreased at a record rate of 75 × 103 km2 d−1, which was 46% faster than the mean rate and 18% faster than in any previous spring season during the satellite era. The decrease of sea ice area was also exceptional and 28% greater than the mean. Anomalous negative retreat occurred in all sectors of the Antarctic but was greatest in the Weddell and Ross Seas. Record negative SIE anomalies for the day of year were recorded from 3 November 2016 to 9 April 2017. Rapid ice retreat in the Weddell Sea took place in strong northerly flow after an early maximum ice extent in late August. Rapid ice retreat occurred in November in the Ross Sea when surface pressure was at a record high level, with the Southern Annular Mode at its most negative for that month since 1968.

Arctic sea ice reduction: the evidence, models and impacts

Recent years have seen dramatic changes in the state of the Arctic sea ice cover. The last 8 years (2007–2014) have seen the eight lowest sea ice summer area extents in the continuous satellite record, which extends back to 1979. The decrease in sea ice area has also been accompanied by a decrease

Change of sea ice content in the Arctic and the associated climatic effects: detection and simulation

Modeling results of the impact of sea surface temperature and sea ice extent changes over the last decades on the formation of weather and climate anomalies are presented. It was found that the Arctic sea ice area reduction may lead to anti-cyclonic regimes’ formation causing anomalously cold winters in particular on the Russian territory. Using simulation with an atmospheric general circulation model, it is shown that the Early 20th Century Warming must have been accompanied by a large negative Arctic sea ice area anomaly in winter time. The results imply a considerable role of long-term natural climate variations in the modern sea ice area decrease. Estimates of the possible probability’s changes of the dangerous events of strong winds and high waves in the Arctic basin and favorable navigation conditions for the Northern Sea Route in the 21st century are made based on numerical model calculations. An increase of extreme wave height is found to the middle of the 21st century for Kara and Chukchi Seas as a consequence of prolonged run length and increased surface winds.

Numerical simulation of the world ocean circulation and its climatic variability for 1948–2007 using the INMOM

The results of simulating global ocean circulation and its interannual variability in 1948–2007 using INM RAS ocean general circulation model INMOM (Institute of Numerical Mathematics Ocean Model) are presented. One of the INMOM versions is also used for the Black Sea dynamics simulation. The CORE datasets were used to set realistic atmospheric forcing. Sea ice area decrease by 2007 was reproduced in the Arctic Ocean that is in good agreement with observations. The interdecadal climatic variability was revealed with significant decrease of Atlantic thermohaline circulation (ATHC) and meridional heat transport (MHT) in North Atlantic (NA) since the late 1990’s. MHT presents decrease of heat transport from NA to the atmosphere since the mid-1990’s. Therefore the negative feedback is revealed in the Earth climate system that leads to reducing of climate warming caused primarily by anthropogenic factor for the last decades. Long-term variability (60 years) of ATHC is revealed as well which influences NA thermal state with 10 year delay. The assumption is argued that this mechanism can make a contribution in the ATHC own long-term variability.

Improvement in Technology on Icebreaker^|^apos;s Performance

Developments of natural resources in the Arctic region are becoming active in the recent years. Commercial use of the northern sea route is taking on realness with a decrease of sea ice area along the Arctic coast. Also Arctic and Antarctic observation is important to clarify a global climatic change. Icebreakers are indispensable to the support for the development, the escort for cargo ships and the polar observation in ice-covered waters. The technology on icebreaker's performance is improving steadily, responding to those missions. This paper shows the typical characteristics of icebreaker and introduces several technologies to improve the performance.

Quantifying the Influence of Atlantic Heat on Barents Sea Ice Variability and Retreat*

Abstract The recent Arctic winter sea ice retreat is most pronounced in the Barents Sea. Using available observations of the Atlantic inflow to the Barents Sea and results from a regional ice–ocean model the authors assess and quantify the role of inflowing heat anomalies on sea ice variability. The interannual variability and longer-term decrease in sea ice area reflect the variability of the Atlantic inflow, both in observations and model simulations. During the last decade (1998–2008) the reduction in annual (July–June) sea ice area was 218 × 103 km2, or close to 50%. This reduction has occurred concurrent with an increase in observed Atlantic heat transport due to both strengthening and warming of the inflow. Modeled interannual variations in sea ice area between 1948 and 2007 are associated with anomalous heat transport (r = −0.63) with a 70 × 103 km2 decrease per 10 TW input of heat. Based on the simulated ocean heat budget it is found that the heat transport into the western Barents Sea sets the boundary of the ice-free Atlantic domain and, hence, the sea ice extent. The regional heat content and heat loss to the atmosphere scale with the area of open ocean as a consequence. Recent sea ice loss is thus largely caused by an increasing “Atlantification” of the Barents Sea.

An assessment and interpretation of the observed warming of West Antarctica in the austral spring

We synthesize variability and trends in multiple analyses of Antarctic near-surface temperature representing several independent source datasets and spatially complete reconstructions, and place these into the broader context of the behavior of other components of the climate system during the past 30–50 years. Along with an annual-mean trend during the past 50 years of about 0.1°C/decade averaged over Antarctica, there is a distinct seasonality to the trends, with insignificant change (and even some cooling) in austral summer and autumn in East Antarctica, contrasting with warming in austral winter and spring. Apart from the Peninsula, the seasonal warming is largest and most significant in West Antarctica in the austral spring since the late 1970s. Concurrent trends in sea ice are independent evidence of the observed warming over West Antarctic, with the decrease in sea ice area in the Amundsen and Bellingshausen Seas congruent with at least 50% of the inland warming of West Antarctica. Trends in near surface winds and geopotential heights over the high-latitude South Pacific are consistent with a role for atmospheric forcing of the sea ice and air temperature anomalies. Most of the circulation trend projects onto the two Pacific South American (PSA) modes of atmospheric circulation variability, while the Southern Annular Mode lacks a positive trend in spring that would otherwise cause a cooling tendency. The largest circulation trend is associated with the PSA-1 mode, a wave-train extending from the tropics to the high Southern latitudes. The PSA-1 mode is significantly correlated with SSTs in the southwestern tropical and subtropical Pacific. The increased SSTs in this region, together with the observed increase in rainfall, suggest that anomalous deep convection has strengthened or increased the occurrence of the Rossby wave-train associated with PSA-1. This hypothesis is supported by results from two ensembles of SST-forced atmospheric general circulation model simulations. Finally, the implications of the seasonality, timing, and spatial patterns of Antarctic temperature trends with respect to interpreting the relative roles of stratospheric ozone depletion, SSTs and increased atmospheric concentrations of greenhouse gasses are discussed.

Increase and decrease of sea ice area in the Sea of Okhotsk: Ice production in coastal polynyas and dynamic thickening in convergence zones

This paper examines the production and reduction of sea ice area in the Sea of Okhotsk. Analyses were carried out for 10 winters (December–April) from 1991/1992 to 2000/2001 using daily data of sea ice velocity and concentration, derived from images of the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave Imager (SSM/I). First, we mapped sea ice divergence, which was calculated from the daily ice velocity field. In the case of offshore winds, high divergence was observed along the coastline, while there existed a broad convergence area with inshore winds. Next, we examined local changes in an area of sea ice. As in the case of ice divergence, ice production and reduction are strongly controlled by wind direction. We found that a large amount of sea ice was produced in coastal areas under offshore wind conditions. The geographical distribution of the ice production area agrees well with that of the well‐known coastal polynya areas. Our estimation shows that 8.7 × 105 km2 yr−1 of sea ice is produced in the northern coastal area, and 3.7 × 105 km2 yr−1 in the Sakhalin coastal area. In contrast, 7.4 × 105 km2 yr−1 of the ice area disappeared in Shantarskiy Bay. This reduction of ice area is mainly caused by dynamic deformation of existing ice forming rafted ice or pressure ridges. This dynamic deformation plays an important role, not only in the reduction of Okhotsk sea ice area, but also in the thickening of ice.

Relationship between synoptic forcing and polynya formation in the Cosmonaut Sea: 1. Polynya climatology

A polynya has been observed in satellite imagery to occur irregularly between the months of July and October in the Cosmonaut Sea. To investigate the processes of formation, maintenance, and decay of these polynyas, a 13‐year climatology of Antarctic atmospheric and surface conditions is assembled from numerical weather prediction model analyses and remotely sensed satellite observations. An analytical technique used previously to identify and track atmospheric low pressure systems is modified to identify polynyas from daily analyses of sea ice area. This information is used to prepare a set of monthly climatological conditions as well as their anomalies when a polynya is present. Previous studies have suggested a link between atmospheric forcing and polynya formation. Along with the drop in sea ice area, there is a drop in sea level pressure as well as an increase in atmospheric wind divergence when the Cosmonaut Sea polynya is present. In some months, the sea ice area decrease is preceded by the passage of an atmospheric low pressure system 1–2 days earlier, but due to the continuous presence of katabatic winds and the coarseness of the ECMWF data, there is not as definitive a relationship between wind divergence and sea level pressure or ice area. Errors associated with the processing of passive microwave remotely sensed data, as well as differences in spatial scale limit that can be determined about the ocean state from the data sets, suggest the need for improved surface classification techniques, as well as regional modeling studies.