scholarly journals Increasing riverine heat influx triggers Arctic sea ice decline and oceanic and atmospheric warming

2020 ◽  
Vol 6 (45) ◽  
pp. eabc4699 ◽  
Author(s):  
Hotaek Park ◽  
Eiji Watanabe ◽  
Youngwook Kim ◽  
Igor Polyakov ◽  
Kazuhiro Oshima ◽  
...  
Keyword(s):  
Sea Ice ◽  
Land Surface ◽  
Heat Budget ◽  
Ocean Model ◽  
Early Summer ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Surface Model ◽  
Arctic Sea ◽  
Atmospheric Warming

Arctic river discharge increased over the last several decades, conveying heat and freshwater into the Arctic Ocean and likely affecting regional sea ice and the ocean heat budget. However, until now, there have been only limited assessments of riverine heat impacts. Here, we adopted a synthesis of a pan-Arctic sea ice–ocean model and a land surface model to quantify impacts of river heat on the Arctic sea ice and ocean heat budget. We show that river heat contributed up to 10% of the regional sea ice reduction over the Arctic shelves from 1980 to 2015. Particularly notable, this effect occurs as earlier sea ice breakup in late spring and early summer. The increasing ice-free area in the shelf seas results in a warmer ocean in summer, enhancing ocean–atmosphere energy exchange and atmospheric warming. Our findings suggest that a positive river heat–sea ice feedback nearly doubles the river heat effect.

scholarly journals Arctic Sea Ice Retreat in 2007 Follows Thinning Trend

2009 ◽  
Vol 22 (1) ◽  
pp. 165-176 ◽  
Author(s):  
R. W. Lindsay ◽  
J. Zhang ◽  
A. Schweiger ◽  
M. Steele ◽  
H. Stern
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Ocean Model ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Ice Thickness ◽  
Sea Ice Extent ◽  
Pacific Side ◽  
Arctic Sea ◽  
The Arctic Ocean

Abstract The minimum of Arctic sea ice extent in the summer of 2007 was unprecedented in the historical record. A coupled ice–ocean model is used to determine the state of the ice and ocean over the past 29 yr to investigate the causes of this ice extent minimum within a historical perspective. It is found that even though the 2007 ice extent was strongly anomalous, the loss in total ice mass was not. Rather, the 2007 ice mass loss is largely consistent with a steady decrease in ice thickness that began in 1987. Since then, the simulated mean September ice thickness within the Arctic Ocean has declined from 3.7 to 2.6 m at a rate of −0.57 m decade−1. Both the area coverage of thin ice at the beginning of the melt season and the total volume of ice lost in the summer have been steadily increasing. The combined impact of these two trends caused a large reduction in the September mean ice concentration in the Arctic Ocean. This created conditions during the summer of 2007 that allowed persistent winds to push the remaining ice from the Pacific side to the Atlantic side of the basin and more than usual into the Greenland Sea. This exposed large areas of open water, resulting in the record ice extent anomaly.

scholarly journals Modeling M2 tidal variability in Arctic Sea-ice drift and deformation

2006 ◽  
Vol 44 ◽  
pp. 418-428 ◽  
Author(s):  
W.D. Hibler ◽  
A. Roberts ◽  
P. Heil ◽  
A.Y. Proshutinsky ◽  
H.L. Simmons ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Basin ◽  
Ocean Model ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Ocean Coupling ◽  
Ice Drift ◽  
Arctic Sea ◽  
Sea Ice Drift ◽  
Tidal Variability

AbstractSemi-diurnal oscillations are a ubiquitous feature of polar Sea-ice motion. Over much of the Arctic basin, inertial and Semi-diurnal tidal variability have Similar frequencies So that periodicity alone is inadequate to determine the Source of oscillations. We investigate the relative roles of tidal and inertial variability in Arctic Sea ice using a barotropic ice–ocean model with Sea ice embedded in an upper boundary layer. Results from this model are compared with ‘levitated’ ice–ocean coupling used in many models. In levitated models the mechanical buoyancy effect of Sea ice is neglected So that convergence of ice, for example, does not affect the oceanic Ekman flux. We use rotary Spectral analysis to compare Simulated and observed results. This helps to interpret the rotation Sense of Sea-ice drift and deformation at the Semi-diurnal period and is a useful discriminator between tidal and inertial effects. Results indicate that the levitated model generates an artificial inertial resonance in the presence of tidal and wind forcing, contrary to the embedded Sea-ice model. We conclude that Sea-ice mechanics can cause the rotational response of ice motion to change Sign even in the presence of Strong and opposing local tidal forcing when a physically consistent dynamic ice–ocean coupling is employed.

scholarly journals Seasonal changes in Arctic sea-ice morphology

2001 ◽  
Vol 33 ◽  
pp. 171-176 ◽  
Author(s):  
Donald K. Perovich ◽  
Jacqueline A. Richter-Menge ◽  
Walter B. Tucker
Keyword(s):  
Sea Ice ◽  
Heat Budget ◽  
Open Water ◽  
Ice Cover ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Ice Surface ◽  
Arctic Sea ◽  
Dynamic Forcing ◽  
Break Up

AbstractThe morphology of the Arctic sea-ice cover undergoes large changes over an annual cycle. These changes have a significant impact on the heat budget of the ice cover, primarily by affecting the distribution of the solar radiation absorbed in the ice-ocean system. In spring, the ice is snow-covered and ridges are the prominent features. The pack consists of large angular floes, with a small amount of open water contained primarily in linear leads. By the end of summer the ice cover has undergone a major transformation. The snow cover is gone, many of the ridges have been reduced to hummocks and the ice surface is mottled with melt ponds. One surface characteristic that changes little during the summer is the appearance of the bare ice, which remains white despite significant melting. The large floes have broken into a mosaic of smaller, rounded floes surrounded by a lace of open water. Interestingly, this break-up occurs during summer when the dynamic forcing and the internal ice stress are small During the Surface Heat Budget of the Arctic Ocean (SHEBA) field experiment we had an opportunity to observe the break-up process both on a small scale from the ice surface, and on a larger scale via aerial photographs. Floe break-up resulted in large part from thermal deterioration of the ice. The large floes of spring are riddled with cracks and leads that formed and froze during fall, winter and spring. These features melt open during summer, weakening the ice so that modest dynamic forcing can break apart the large floes into many fragments. Associated with this break-up is an increase in the number of floes, a decrease in the size of floes, an increase in floe perimeter and an increase in the area of open water.

The Thinning of Arctic Sea Ice, 1988–2003: Have We Passed a Tipping Point?

2005 ◽  
Vol 18 (22) ◽  
pp. 4879-4894 ◽  
Author(s):  
R. W. Lindsay ◽  
J. Zhang
Keyword(s):  
Sea Ice ◽  
Open Water ◽  
Ocean Model ◽  
Tipping Point ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
First Year ◽  
Positive Feedbacks ◽  
Cooling Period ◽  
Arctic Sea

Abstract Recent observations of summer Arctic sea ice over the satellite era show that record or near-record lows for the ice extent occurred in the years 2002–05. To determine the physical processes contributing to these changes in the Arctic pack ice, model results from a regional coupled ice–ocean model have been analyzed. Since 1988 the thickness of the simulated basinwide ice thinned by 1.31 m or 43%. The thinning is greatest along the coast in the sector from the Chukchi Sea to the Beaufort Sea to Greenland. It is hypothesized that the thinning since 1988 is due to preconditioning, a trigger, and positive feedbacks: 1) the fall, winter, and spring air temperatures over the Arctic Ocean have gradually increased over the last 50 yr, leading to reduced thickness of first-year ice at the start of summer; 2) a temporary shift, starting in 1989, of two principal climate indexes (the Arctic Oscillation and Pacific Decadal Oscillation) caused a flushing of some of the older, thicker ice out of the basin and an increase in the summer open water extent; and 3) the increasing amounts of summer open water allow for increasing absorption of solar radiation, which melts the ice, warms the water, and promotes creation of thinner first-year ice, ice that often entirely melts by the end of the subsequent summer. Internal thermodynamic changes related to the positive ice–albedo feedback, not external forcing, dominate the thinning processes over the last 16 yr. This feedback continues to drive the thinning after the climate indexes return to near-normal conditions in the late 1990s. The late 1980s and early 1990s could be considered a tipping point during which the ice–ocean system began to enter a new era of thinning ice and increasing summer open water because of positive feedbacks. It remains to be seen if this era will persist or if a sustained cooling period can reverse the processes.

scholarly journals Influence of stochastic sea ice parametrization on climate and the role of atmosphere–sea ice–ocean interaction

2014 ◽  
Vol 372 (2018) ◽  
pp. 20130283 ◽  
Author(s):  
Stephan Juricke ◽  
Thomas Jung
Keyword(s):  
Sea Ice ◽  
Coupled Model ◽  
Ocean Model ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Polar Regions ◽  
Stochastic Perturbations ◽  
Arctic Sea ◽  
The Mean ◽  
Mean Climate

The influence of a stochastic sea ice strength parametrization on the mean climate is investigated in a coupled atmosphere–sea ice–ocean model. The results are compared with an uncoupled simulation with a prescribed atmosphere. It is found that the stochastic sea ice parametrization causes an effective weakening of the sea ice. In the uncoupled model this leads to an Arctic sea ice volume increase of about 10–20% after an accumulation period of approximately 20–30 years. In the coupled model, no such increase is found. Rather, the stochastic perturbations lead to a spatial redistribution of the Arctic sea ice thickness field. A mechanism involving a slightly negative atmospheric feedback is proposed that can explain the different responses in the coupled and uncoupled system. Changes in integrated Antarctic sea ice quantities caused by the stochastic parametrization are generally small, as memory is lost during the melting season because of an almost complete loss of sea ice. However, stochastic sea ice perturbations affect regional sea ice characteristics in the Southern Hemisphere, both in the uncoupled and coupled model. Remote impacts of the stochastic sea ice parametrization on the mean climate of non-polar regions were found to be small.

From red to white: the time-varying nature of ocean heat flux to Arctic sea ice

2020 ◽  
Author(s):  
Srikanth Toppaladoddi ◽  
Andrew Wells
Keyword(s):  
Heat Flux ◽  
Sea Ice ◽  
Time Series Data ◽  
Heat Budget ◽  
Temporal Variations ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Series Data ◽  
Fluctuation Analysis ◽  
Arctic Sea

<p>Arctic sea ice is one of the most sensitive components of the Earth’s climate system. The underlying ocean plays an important role in the evolution of the ice cover through its heat flux at the ice-ocean interface which moderates ice growth and melt. Despite its importance, the spatio-temporal variations of this heat flux are not well understood. In this work, we combine direct numerical simulations of turbulent convection over fractal surfaces and analysis of time-series data from the Surface Heat Budget of the Arctic Ocean (SHEBA) program using Multifractal Detrended Fluctuation Analysis (MFDFA) to understand the nature of fluctuations in this heat flux. We identify key physical processes associated with the observed Hurst exponents calculated by the MFDFA, and how these evolve over time. We also discuss ongoing work on constructing simple stochastic models of the ocean heat flux to the ice, and potential use as a parameterisation.</p>

scholarly journals Arctic Sea Ice and Freshwater Changes Driven by the Atmospheric Leading Mode in a Coupled Sea Ice–Ocean Model

2003 ◽  
Vol 16 (13) ◽  
pp. 2159-2177 ◽  
Author(s):  
Xiangdong Zhang ◽  
Moto Ikeda ◽  
John E. Walsh
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Ocean Model ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Siberian River ◽  
The North ◽  
New Findings ◽  
Arctic Sea ◽  
The Arctic Ocean

Abstract Observational and modeling studies have indicated recent large changes of sea ice and hydrographic properties in the Arctic Ocean. However, the observational database is sufficiently sparse that the mechanisms responsible for the recent changes are not fully understood. A coupled Arctic ocean–sea ice model forced by output from the NCEP–NCAR reanalysis is employed to investigate the role that the leading atmospheric mode has played in the recent changes of the Arctic Ocean. A modified Arctic Oscillation (AO) index is derived for the region poleward of 62.5°N in order to avoid ambiguities in the distinction between the conventional AO and the North Atlantic Oscillation index. The model results indicate that the AO is the driver of many of the changes manifested in the recent observations. The model shows reductions of Arctic sea ice area and volume by 3.2% and 8.8%, respectively, when the AO changes from its negative to its positive phase. Concurrently, freshwater storage decreases by about 2%, while the sea ice and freshwater exports via Fram Strait increase substantially. The changes of sea ice and freshwater storage are strikingly asymmetric between the east and the west Arctic. Notable new findings include 1) the interaction of the dynamic and thermodynamic responses in the sense that changes of sea ice growth and melt are driven by, and feed back negatively to, the dynamically (transport) driven changes of sea ice volume; and 2) the compatibility of the associated freshwater changes with recently observed changes in the salinity of the upper Arctic Ocean, thereby explaining the observed salinity variations by a mechanism that is distinct from, but complementary to, the altered circulation of Siberian river water. In addition, the enhanced freshwater export could be a contributing factor to the increased salinity in the Arctic Ocean. The results of the simulations indicate that Arctic sea ice and freshwater distributions change substantially if one phase of the AO predominates over a decadal timescale. However, such results are based on an idealization of the real-world situation, in which the pattern of forcing varies interannually and the number of positive-AO years varies among decades.

scholarly journals Delay in Arctic Sea Ice Freeze-Up Linked to Early Summer Sea Ice Loss: Evidence from Satellite Observations

2021 ◽  
Vol 13 (11) ◽  
pp. 2162
Author(s):  
Lei Zheng ◽  
Xiao Cheng ◽  
Zhuoqi Chen ◽  
Qi Liang
Keyword(s):  
Sea Ice ◽  
Short Wave ◽  
Early Summer ◽  
Arctic Sea Ice ◽  
Radiation Budget ◽  
The Arctic ◽  
Wave Radiation ◽  
Synthetic Approach ◽  
Sea Ice Extent ◽  
Arctic Sea

The past decades have witnessed a rapid loss of the Arctic sea ice and a significant lengthening of the melt season. The years with the lowest summertime sea ice minimum were found to be accompanied by the latest freeze-up onset on record. Here, a synthetic approach is taken to examine the connections between sea ice melt timing and summer sea ice evolution from the remote sensing perspective. A 40-year (1979–2018) satellite-based time-series analysis shows that the date of autumn sea ice freeze-up is significantly correlated with the sea ice extent in early summer (r = −0.90, p < 0.01), while the spring melt onset is not a promising predictor of summer sea ice evolution. The delay in Arctic sea ice freeze-up (0.61 days year−1) in the Arctic was accompanied by a decline in surface albedo (absolute change of −0.13% year−1), an increase in net short-wave radiation (0.21 W m−2 year−1), and an increase in skin temperature (0.08 °C year−1) in summer. Sea ice loss would be the key reason for the delay in autumn freeze-up, especially in the Laptev, East-Siberian, Chukchi and Beaufort Seas, where sea ice has significantly declined throughout the summer, and strong correlations were found between the freeze-up onset and the solar radiation budget since early summer. This study highlights a connection between the summer sea ice melting and the autumn refreezing process through the ice-albedo feedback based on multisource satellite-based observations.

scholarly journals Early predictors of seasonal Arctic sea-ice volume loss: the impact of spring and early-summer cloud radiative conditions

2020 ◽  
pp. 1-9
Author(s):  
Michalea D. King ◽  
Dana E. Veron ◽  
Helga S. Huntley
Keyword(s):  
Sea Ice ◽  
Early Summer ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Observation Data ◽  
Volume Loss ◽  
Radiative Fluxes ◽  
Ice Volume ◽  
Arctic Sea ◽  
The Impact

Abstract Clouds play an important role in the Arctic surface radiative budget, impacting the seasonal evolution of Arctic sea-ice cover. We explore the large-scale impacts of springtime and early summer (March through July) cloud and radiative fluxes on sea ice by comparing these fluxes to seasonal ice volume losses over the central Arctic basin, calculated for available observational years 2004–2007 (ICESat) and 2011–2017 (CryoSat-2). We also supplement observation data with sea-ice volume computed from the Pan-Arctic Ice–Ocean Modeling and Assimilation System (PIOMAS) during summer months. We find that the volume of sea ice lost over the melt season is most closely related to observed downwelling longwave radiation in March and early summer (June and July) longwave cloud radiative forcing, which together explain a large fraction of interannual variability in seasonal sea-ice volume loss (R2 = 0.71, p = 0.007). We show that downwelling longwave fluxes likely impact the timing of melt onset near the sea-ice edge, and can limit the magnitude of ice thickening from March to April. Radiative fluxes in June and July are likely critical to seasonal volume loss because modeled data show the greatest ice volume reductions occur during these months.

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