Wednesday, September 19, 2018

Current Sea Ice



 

I noticed an odd report that overstated the ice situation and this woke me up to put up an update.   This year, the north west passage has remain closed off and quite badly as well.  No one is going through there this year.  In fact it would be challenging for a viking long boat as well although the southern route is reachable and it is clear.

Yet the total ice cover remains close to the now established 2008 - 2018 channel to keep that fully intact.  The Russian route is also wide open and you could sail a fleet through there.

The restoration of Medieval sea ice conditions continues and that particular cycle lasted several centuries and allowed a steady  movement of support and trade between Greenland and Vinland which was the Cowichan valley on Vancouver Island.

Considering that it should also be quite apparent that they also established meaningful Walrus hunting bases on Ungava and through to Hudson Bay.  It is also plausible that they built out a community in James Bay far earlier than their actual abandonment of Greenland.  Thus actual abandonment, although necessarily organized and taking at least two seasons was also well fed through the walrus hunt.  At the same time they would have used their shipping to move as many as possible to New England which could not absorb more than a few hundred from a population reported to be 10,000.  The walrus hunt was close by and a handful of ships could move hundreds every week to Ungava.
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Current State of the Sea Ice Cover

J. C. Comiso, C. L. Parkinson, T. Markus, D. J. Cavalieri and R. Gersten

https://neptune.gsfc.nasa.gov/csb/index.php?section=234
 
The sea ice cover is one of the key components of the polar climate system. It has been a focus of attention in recent years, largely because of a strong decrease in the Arctic sea ice cover and modeling results that indicate that global warming could be amplified in the Arctic on account of ice-albedo feedback. This results from the high reflectivity (albedo) of the sea ice compared to ice-free waters. A satellite-based data record starting in late 1978 shows that indeed rapid changes have been occurring in the Arctic, where the ice coverage has been declining at a substantial rate. In contrast, in the Antarctic the sea ice coverage has been increasing although at a lesser rate than the decreases in the Arctic. Shown below are up-to-date satellite observations of the sea ice covers of both the Arctic and the Antarctic, along with comparisons with the historical satellite record of more than 37 years. The plots and color-coded maps are chosen to provide information about the current state of the sea ice cover and how the most current daily data available compare with the record lows and record highs for the same date during the satellite era. Sea ice concentration is the percent areal coverage of ice within the data element (grid cell). Sea ice extent is the integral sum of the areas of all grid cells with at least 15% ice concentration, while sea ice area is the integral sum of the product of ice concentration and area of all grid cells with at least 15% ice concentration. The dashed vertical line indicates the date of the latest plotted and mapped data.

Figure 1: 10-year averages between 1979 and 2008 and yearly averages for 2007, 2012, and 2016 of the daily (a) ice extent and (b) ice area in the Northern Hemisphere and a listing of the extent and area of the current, historical mean, minimum, and maximum values in km2.


Figure 2: Color-coded map of the daily sea ice concentration in the Northern Hemisphere for the indicated recent date along with the contours of the 15% edge during the years with the least extent of ice (in red) and the greatest extent of ice (in yellow) during the period from November 1978 to the present. The extents in km2 for the current and for the years of minimum and maximum extents are provided below the image. The different shades of gray over land indicate the land elevation with the lightest gray being the highest elevation.
Figure 3: 10-year averages between 1979 and 2008 and yearly averages for 2012, 2014, and 2016 of the daily (a) ice extent and (b) ice area in the Southern Hemisphere and a listing of the extent and area of the current, historical mean, minimum, and maximum values in km2.
Figure 4: Color-coded map of the daily sea ice concentration in the Southern Hemisphere for the indicated recent date along with the contours of the 15% edge during the years with the least extent of ice (in red) and the greatest extent of ice (in yellow) during the period from November 1978 to the present. The extents in km2 for the current and for the years of minimum and maximum extents are provided below the image. The different shades of gray over land indicate the land elevation with the lightest gray being the highest elevation.

Figure 5. Seasonal cycle of Northern Hemisphere sea ice extents (a) and areas (b), given as daily averages, for the years 2007 through 2016. The vertical line represents the last data point plotted.

Figure 6. Seasonal cycle of Southern Hemisphere sea ice extents (a) and areas (b), given as daily averages, for the years 2007 through 2016. The vertical line represents the last data point plotted.

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