sea ice

During our lifetime, the polar ice caps have endured both summer and winter. Depending on the season, the poles can experience a range of either 24 hours of total sunlight or 24 hours of total darkness. This understandably, has an impact on the sea ice extent as it waxes and wanes over the seasons. This is all natural variability, but on an annual basis.

This graphic very nicely shows the range of solar heating that occurs at the poles over the course of a year. The most solar heating anywhere on the globe? - the arctic in July.

So what is the annual sea ice extent. The Multisatellite Analyzed Sea Ice Extent (MASIE) NSIDC out of the University of Colorado. NSIDC MASIE Sea Ice Extent: https://nsidc.org/data/seaice_index/masie.html

Sea ice extent is defined as the combined area of all ice concentrations greater than or equal to 15%. (though some researchers use up to 30 or 50% in their measurements)

Some would argue, however, that the polar sea ice is receding over the years due to climate change. Is this true? Is the polar ice receding?

Nasa

Nasa puts out a graphic on sea ice extent going back to the start of the satellite era.

There is a slight problem with their graphic - it starts in 1979 and conveniently does not show any sea ice extent before that period, yet, we obviosly

There is even a problem wiht the NOAA graphic. It does not show data from before the '70's but it turns out we have data for that as well. The DOE has been tracking sea ice extent back almost to the first world war. When you superimpose the graphs it tells a very different story.

Here's the relevant excerpt from the report:

"Sea Ice Extent

Observations of sea ice extent show considerable interannual variability

but no clear long-term trend between 1920 and 1975 (Figure 5.3). However, climate model simulations suggest that increased CO2 concentrations could lead to a reduction in Arctic sea ice extent by about 5-10% per degree Celsius of global warming."

Reference: Carbon Dioxide Research: A Summary Report. DOE/ER-0582(December 1985). Office of Energy Research, U.S. Department of Energy.

So I did track down the DOE data and plotted it along with the SDIC data

Southern Hemisphere

Graphics

Not using

RESEARCH

>>> what is a good source of time series data for sea ice extent for 1920 - 198

... 0 To obtain a reliable time series of sea ice extent for the period from 1920 to 1980, you can consider the following sources and methods:

1. Historical Sea Ice Extent Dataset (HadISI): This dataset is part of

the Hadley Centre's suite of climate datasets and provides monthly mean Arctic and Antarctic sea ice extents from 1870 to present. The data for the early period are based on reconstructions using historical observations, such as ship reports and coastal station records. You can access this dataset through the Met Office Hadley Centre website or via the British Oceanic Data Centre (BODC).

Link: https://www.metoffice.gov.uk/hadobs/datasets/sea-ice-extent-hadis

2. Polar Science Center's Arctic Sea Ice Extent Dataset: This dataset,

created by the University of Washington's Polar Science Center, provides daily and monthly sea ice extent data for the Arctic from 1978 to present using satellite observations. To extend your time series back to 1920, you can combine this dataset with reconstructions or historical observations mentioned above.

Link: https://psc.apl.uw.edu/data/sea-ice-extent

3. NSIDC Sea Ice Extent Dataset: The National Snow and Ice Data Center

(NSIDC) provides a monthly sea ice extent time series for both the Arctic and Antarctic, based on satellite observations from 1978 to present. As with other sources, you'll need to combine it with historical reconstructions to cover the period from 1920 to 1977.

Link: https://nsidc.org/data/sea-ice-extent/

To create a consistent time series covering the entire period from 1920 to 1980, you might need to combine data from different sources and methods. It's essential to understand the strengths and limitations of each dataset and choose appropriate methods for data merging or interpolation.

Here are some references to help guide your research on historical sea ice extent:

• Vinnikov, K.Y., & Groisman, P.Y. (2008). Global Sea Ice Extent Reconstruction from 1874 to Present: Methodology and Analysis of Results. Journal of Geophysical Research, 113(C10), C10016.
• Zwally, H.J., et al. (2007). AMSR-E Arctic sea ice extent retrieval algorithm and results. IEEE Transactions on Antennas and Propagation, 55(4), 918-930.
• National Snow and Ice Data Center (NSIDC) (n.d.). Sea Ice Extent Dataset. Retrieved from https://nsidc.org/data/sea-ice-extent/

>>> what other time series datasets do we have on sea ice extend prior to 1978

Before the era of satellite observations, which began in the late 1970s, sea ice extent was primarily monitored using ground-based observations, ship reports, and occasional aerial surveys. Several time series datasets exist for sea ice extent before 1978, although they may have lower spatial resolution and higher uncertainties compared to satellite-based data. Here are some key datasets and sources of sea ice extent prior to 1978:

1. HadISI dataset (Hadley Centre's Historical Sea Ice Extent): This dataset provides monthly mean Arctic and Antarctic sea ice extents from 1870 to present, including the pre-satellite era. The data are reconstructed using historical observations, such as ship reports and coastal station records.

   Link:

https://www.metoffice.gov.uk/hadobs/datasets/sea-ice-extent-hadis

2. Global Sea Ice Extent Dataset (GSIED): This dataset, created by the National Oceanic and Atmospheric Administration (NOAA), provides monthly sea ice extent data for both Arctic and Antarctic regions from 1870 to present. The GSIED combines various observational sources, including ship reports, weather charts, coastal observations, and occasional aerial surveys.

   Link: https://www.esrl.noaa.gov/psd/data/gridded/data.gsied.html

3. Polar Science Center's Arctic Sea Ice Extent Dataset: Although this dataset primarily focuses on satellite-era data (1978 to present), it also includes historical reconstructions back to 1850. The earlier part of the dataset is based on a combination of observations, such as those from the International Arctic Buoy Programme and other historical sources.

   Link: https://psc.apl.uw.edu/data/sea-ice-extent

4. National Snow and Ice Data Center (NSIDC) Sea Ice Extent Dataset: While this dataset mainly covers the satellite era, NSIDC provides additional information on historical observations and reconstructions used to extend their time series back to 1900 for some regions.

   Link: https://nsidc.org/data/sea-ice-extent/

5. Arctic Climate Archive System (ACAS): This archive contains various historical datasets related to Arctic sea ice, including observations from ship reports, weather charts, and coastal stations. Some of these data have been used in the creation of reconstructed sea ice extent time series.

   Link: https://aca.isac.ku.dk/index.php/acas

6. British Oceanic Data Centre (BODC): BODC holds various historical sea ice datasets, including observations from ships and coastal stations. Some of these data can be combined to create time series of sea ice extent.

   Link: https://www.bodc.ac.uk/data/

To create a consistent time series covering the pre-satellite era (1920-1978), you may need to combine data from different sources and methods, considering their strengths and limitations. It's essential to understand that uncertainties will likely be higher for earlier periods due to fewer observations and lower spatial resolution.

References:

• Vinnikov, K.Y., & Groisman, P.Y. (2008). Global Sea Ice Extent Reconstruction from 1874 to Present: Methodology and Analysis of Results. Journal of Geophysical Research, 113(C10), C10016.
• Fetterer, F.I., et al. (2019). Global sea ice extent from passive microwave satellite sensors, version 3. Boulder, Colorado, USA: NOAA/Earth System Research Laboratory Physical Sciences Laboratory.
• Stroeve, C.C., et al. (2014). Sea‐level pressure and Arctic sea-ice variability: Twentieth century trends and historical context. Journal of Climate, 27(9), 3178-3196.
• National Snow and Ice Data Center (NSIDC) (n.d.). Historical Observations of Sea Ice Extent. Retrieved from https://nsidc.org/data/sea-ice-extent/historical-observations