Antártida

¿pq solo en el mar de Ross?

 

During the southern hemisphere spring in 2016, Antarctic sea ice suddenly shrank, leading to a series of months (extending into the 2016 to 2017 austral summer) with the lowest monthly average extents in the satellite data record. This January, Antarctic sea ice was the second lowest ice extent in the 44-year record (Figure 5a). Regionally, ice extent is tracking below levels observed for 2017 in the Indian and Pacific sectors, but above levels for that year in other sectors (Figure 5b). In 2017, only the Ross Sea region had record low extent, so it was the driver of the overall record low hemispheric extent. Similarly, this year none of the individual regions have record low extents, but all are well below average leading to the second lowest Antarctic sea ice in the satellite record, above 2017.

The more moderate extent levels since the record lows in 2016 to 2017 result in a small, not statistically significant (at the 95 percent level) positive trend. Climate models simulating the response to anthropogenic greenhouse gas emissions suggest that Antarctic sea ice should be decreasing. So there is a seeming contradiction between the observations and the models. One possibility is that natural variability is higher than the models indicate and that natural variability may still dominate the Antarctic sea ice trends. A new study led by R. Fogt looked at an ensemble of reconstructions of Antarctic sea ice extent since 1905 using sea level pressure, air temperatures, and indices of climate variability. This study argues that the seasonally observed positive trends since 1979 are unusual over the twentieth century, and that a shift occurred around 1960, before routine satellite observations began. This hints that there is indeed pronounced decadal scale variability in ocean and atmospheric conditions that influence Antarctic sea ice. Whether the low ice conditions of recent years represent a new decadal-scale shift remains to be seen.

https://nsidc.org/arcticseaicenews/

revisión del modelo geotermal antártico

Antarctica ice sheet basal melting enhanced by high mantle heat
Author links open overlay panelIrina M.Artemievaabcd
https://doi.org/10.1016/j.earscirev.2022.103954
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Abstract

Antarctica is losing ice mass by basal melting associated with processes in deep Earth and reflected in geothermal heat flux. The latter is poorly known and existing models based on disputed assumptions are controversial. Here I present a new geophysical model for lithospheric thickness and mantle heat flux for the entire Antarctica and demonstrate that significant parts of the East Antarctica craton have lost the cratonic lithosphere signature and the entire West Antarctica has a highly extended lithosphere, consistent with its origin as a system of back-arc basins. I conclude that the rate of Antarctica ice basal melting is significantly underestimated: (i) the area with high heat flux is double in size and (ii) the amplitude of the high heat flux anomalies is 20–30% higher than in previous results. Extremely high heat flux (>100 mW/m2) in almost all of West Antarctica, continuing to the South Pole region, and beneath the Lake Vostok region in East Antarctica requires a thin (<70 km) lithosphere and shallow mantle melting, caused by recent geodynamic activity. This high heat flux may promote sliding lubrication and result in dramatic reduction of ice mass, such as in Heinrich events. The results form basis for re-evaluation of the Antarctica ice-sheet dynamics models with consequences for global environmental changes.

https://www.sciencedirect.com/science/article/pii/S0012825222000381

https://earth.gsfc.nasa.gov/cryo/data/current-state-sea-ice-cover

https://mobile.twitter.com/collau7/status/1496626152869445639

Sobre el mínimo de banquisa antártica este año, otra visión.

La zona en la que se concentra casi exclusivamente la falta de hielo este año tuvo una anomalía de temp en Enero de -2,5ºC respecto a 1991-2020. Parece evidente que predominó mucho el viento sur por allí, llevando aire frío del continente y a su vez mandando el hielo a tomar por culo a aguas cálidas, donde se derritió una zona muy extensa.
No todo es cosa de más calor, que por aquella zona más bien brilla por su ausencia, la deriva del hielo diría que ha sido tremendamente determinante en este caso.

Un saludo.

Proyecto de centro subantártico
Cabo de Hornos,
https://bipdata.ministeriodesarrollosocial.gob.cl/profile/iniciativa/301165940

Tremendo como debe ser estar por allí ahora, hay fuertes vientos en toda la vertical y en todo el estrecho,
En Buena Esperanza más débiles en superficie.

Creció 5.305 kilómetros cuadrados entre 2009 y 2019

https://tc.copernicus.org/articles/17/2059/2023/

Retroalimentación climática global reciente controlada por el enfriamiento del Océano Austral.

https://www.nature.com/articles/s41561-023-01256-6

Retroalimentación climática global reciente controlada por el enfriamiento del Océano Austral.

https://www.nature.com/articles/s41561-023-01256-6

Pero hay que señalar que el estudio se centra en el periodo 1979 -2013.

Se revela una mayor acumulación de capas de hielo en la Antártida y tasas de derretimiento de la superficie con una resolución de 2 km

https://www.nature.com/articles/s41467-023-43584-6

https://twitter.com/collau7/status/1737471838249189506

Con datos desde 2002, parecen coincidir los periodos de mayor extensión de hielo marino con las mayores pérdidas de hielo continental (entorno a -250Gt/año), mientras que en los periodos de menor extensión de hielo marino no solo no desciende la masa continental de hielo, sino que incluso aumenta. En teoría porque al haber menos hielo rodeando la Antártida llega más aire cálido y húmedo, produciendo nevadas muy importantes que compensan o superan la pérdida de los glaciares al mar y el deshielo superficial veraniego. Habrá que ver las próximas décadas, pero en los últimos 20 años, aunque parezca contradictorio se podría decir que: menos banquisa antártica=más calor=menor subida del nivel del mar (por mayor acumulación de nieve continental)

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