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Sea ice formation over open water exerts critical control on polar atmosphere‐ocean‐ice interactions, but is only crudely represented in sea ice models. In this study, a collection depth parameterization of new ice for flux polynya models is modified by including the sea ice concentration and ice growth rate as additional factors. We evaluated it in a climate model BCC‐CSM2‐MR and found that it improves simulation of Antarctic sea ice concentration and thickness in most of Indian and Atlantic sectors. Disagreement between the observed Antarctic sea ice expansion during 1981–2014 and the modeled decline still exists but is mitigated when the modified scheme is implemented. Further analysis indicates that these improvements are associated with the overcoming of premature closure of open water, which enhances the response of ocean to surface wind intensification during 1981–2014, and consequently slowdowns the sea surface temperature increase and the resulting Antarctic sea ice reduction. Plain Language Summary Open water ice formation critically modulates sea ice variations and the associated polar atmosphere‐ocean interaction, but is not well represented in sea ice models. In this study, a modified collection depth parameterization of new ice based on an existing scheme is presented after including sea ice concentration and ice growth rate as additional factors. We evaluated this modified scheme in BCC‐CSM2‐MR and found that it can improve the simulation of mean Antarctic sea ice thickness and concentration in winter as well as Antarctic sea ice expansion from 1981 to 2014. Further analysis implies that these improvements can be attributed to the overcoming of the premature closure of open water areas in model simulations. Key Points A modified collection thickness parameterization of new ice suitable for large‐scale climate simulations is presented It improves the simulation of Antarctic sea ice thickness and concentration, as well as Antarctic sea ice expansion during 1981–2014 The improved simulations can be attributed to the overcoming of the premature closure of open water areas where new ice forms

Discusses the effects of ice on our physical environment.

The observed decline of sea ice in the Arctic, if it persists into the future, can create more favorable conditions for shipping activity in the region. To estimate possible changes in key sea ice characteristics over the next two decades, we use high‐resolution climate models. The focus is on two shipping routes: the Northwest Passage and the Northeast Passage. In addition to more traditionally analyzed ice concentration and thickness, we present projected changes in ice strength and pressure, which are especially relevant for shipping hazards. Along both routes, the mean September values of ice strength and pressure, projected for the period 2041–2050, decrease by an order of magnitude relative to the period 2015–2024. The decrease is largely driven by changes in ice concentration, rather than thickness or velocity. Increasing ocean resolution from eddy‐present to eddy‐rich leads to less reduction of sea ice area, volume and strength with global warming.

\"Giant icebergs are cracking off ice shelves and splashing into the oceans below. Ice sheets are melting, sending more and more water rushing into the sea. What on Earth is causing this melting ice? As Earth's climate is changing, rising temperatures are causing catastrophic melting. Uncover the problems of climate change, explore its impact on Earth's ice, and dive into what we can do to help. Approachable text and engaging images bring this timely topic to life\"-- Provided by publisher.

This study presents the first dataset of physical and textural properties of sea ice collected in the South Atlantic and Indian Ocean sector of the Antarctic marginal ice zone (MIZ). Observations of sea ice from this region in the austral spring 2019, including sea-ice core temperature, salinity, crystal size, texture, oxygen isotopes and stratigraphy, were used in conjunction with a Lagrangian back-tracking algorithm and atmospheric reanalyses. This method relates the reconstructed synoptic conditions to sea-ice growth along the transect. A significant difference was found between the stratigraphy of consolidated pack ice samples collected at the same latitude and spanning over 550 km eastwards. The eastward group was found to have more disturbances in their stratigraphy which is attributed to the highly variable atmospheric and sea-ice conditions together with varying wave penetration through the sea-ice pack, notably during the passage of an intense polar cyclone, while the westward group showed no signs of disturbance or deformation. These results indicate that consolidated Antarctic sea-ice floes of similar thickness and from the same latitude in the MIZ have distinct stratigraphic properties, which will influence their physical and biogeochemical features.

Mesoscale eddies, generated by lateral gradients in salinity and temperature in the Arctic marginal ice zone, are known to modulate the melting of sea ice. Yet, it remains unclear if eddies modify sea ice growth during the freezing season. Here, we use idealized spin‐down simulations of a front to explore the sea ice growth above an eddying ocean. In the presence of eddies, mixing of the sea surface temperature and salinity induces spatial variability in the heat and salt fluxes at the ice‐ocean interface, imprinting spatial variability on the sea ice thickness. Sea ice thickness shows an order of magnitude more spatial variability in our simulations with strong eddies compared to those without. Increased spatial heterogeneity in the sea ice could make it more brittle and affect its evolution. This effect may become more pronounced as the Arctic transitions to a summer open‐ocean regime and the eddy field intensifies. Plain Language Summary Lateral variations of salinity and temperature in the Arctic Ocean caused by the melting or freezing of ice can result in ocean eddies (vortex‐like features up to ∼100${\\sim} 100$km in size). Previous studies have focused on how these eddies affect sea ice melting. However, it is not clear if eddies also play a role when the ice forms. Here, we use numerical simulations to see how these eddies influence the growth of sea ice. Eddies affect the temperature and salinity distributions at the ocean surface, which, in turn, modulate the thickness of sea ice as it forms. This eddy effect in the sea ice is important because it could impact the transitional zone between the open ocean and ice covered Arctic. Understanding these eddy‐sea ice interactions is crucial to better understand the current and future states of the Arctic sea ice as it transitions to a summer ice free ocean. Key Points Mesoscale ocean eddies imprint heterogeneity on sea‐ice thickness during the freezing season Eddies induce heterogeneity in sea‐ice thickness by locally changing heat and salt fluxes at the ice‐ocean interface An increase in eddy field intensity leads to an increase in sea ice heterogeneity

\"The Arctic is thawing. Vanishing Ice is a powerful depiction of the dramatic transformation of the cryosphere--the world of ice and snow--and its consequences for the human world. Delving into the major components of the cryosphere, including ice sheets, valley glaciers, permafrost, and floating ice, Vivien Gornitz gives an up-to-date explanation of key current trends in the decline of ice mass. Drawing on a long-term perspective gained by examining changes in the cryosphere and corresponding variations in sea level over millions of years, she demonstrates the link between thawing ice and sea-level rise to point to the social and economic challenges on the horizon. Gornitz highlights the widespread repercussions of ice loss, which will affect countless people far removed from frozen regions, to demonstrate why the big meltdown matters to us all\"-- Provided by publisher.

For jointly assimilating sea‐ice concentration (SIC) and sea‐ice thickness (SIT) observations into a global coupled climate system model consisting of sea‐ice component with multiple sea‐ice categories, we propose a new sea‐ice analysis update scheme in an ensemble assimilation framework and compare it with some previously used schemes. Different from the conventional scheme that often assigns SIC/SIT analysis to multiple sea‐ice categories according to the background ratios and thus directly updates the corresponding variables in model (i.e., direct‐update scheme), the new scheme converts SIC/SIT analysis into ice heating term to adjust the ice enthalpy using model freezing/melting physics and further updates the model sea‐ice state (i.e., enthalpy‐adjusting scheme). It has a capability in particularly adjusting multiple sea‐ice variables in addition to SIC and SIT in a coordinated way, and avoiding the artificial addition or elimination of sea‐ice in analysis that is often adopted in the direct‐update scheme. Evaluated by several sets of experiments assimilating satellite‐derived Arctic sea‐ice observations, the enthalpy‐adjusting scheme performs better than the direct‐update scheme in analysis of the Arctic SIT. Further, 4‐week forecasts after assimilation initialization exhibit slow growth of forecast error. Compared to the direct‐update scheme, the enthalpy‐adjusting scheme initialized forecasts show comparable skills in the SIC but significantly higher skills in the SIT, especially in the Arctic sea‐ice edge areas. These results highlight advantage of the enthalpy‐adjusting scheme that has promise to improve coupled data assimilation and reduce climate prediction uncertainty. Plain Language Summary Effective assimilation of sea‐ice observation is an important task for building coupled data assimilation and prediction system based on the climate system model. For the establishment of coupled sea‐ice assimilation technique, how to ensure the coordination of multiple variables is a crucial issue. Although sea‐ice's ablation and accretion are mainly thermodynamic‐driven and most sea‐ice models focus on describing the enthalpy properties of ice, till now there are few studies to implement enthalpy‐based sea‐ice assimilation in complex climate model due to the difficulty of accurately estimating the enthalpy in observational space and model space. This study proposes an enthalpy‐adjusting scheme that uses sea‐ice concentration/thickness (SIC/SIT) analysis to adjust ice enthalpy and further update the sea‐ice state in model. Compared to the conventional scheme that uses SIC/SIT analysis to directly update the corresponding model variables, the new scheme produces better analysis of the Arctic SIT at the assimilation stage, and also higher subseasonal forecast skill of the Arctic SIT at the forecast stage. The study indicates the obvious superiority of the enthalpy‐adjusting analysis scheme in sea‐ice forecasting and highlights the importance of multivariate coordinated assimilation for improving climate model's forecast performance. Key Points A new sea‐ice analysis update scheme based on enthalpy‐adjusting strategy is developed for coordinated sea‐ice multivariate assimilation The scheme is capable of providing skillful analysis of sea‐ice concentration/thickness (SIC/SIT) in the Arctic The scheme can produce apparently lower error of SIT in subseasonal forecasting of Arctic sea‐ice