Guest essay by Robert A Cook, PE – Re-Blogged From http://www.WattsUpWithThat.com
Sea ice concentration, north and south poles as observed by satellite. Image from University of Illinois Cryosphere Today
In particular, for the twenty-second of each month, we will calculate and present for discussion:
- that day’s solar radiation level at top of atmosphere (TOA),
- that day’s declination angle (the tilt of the earth’s axis towards or away from the solar plane),
- that day’s average Antarctic and Arctic sea ice area and extents,
- an estimate of the latitude of the edge of that day’s Antarctic and Arctic areas,
- at the edge of the sea ice for that day, estimate the total reflected and absorbed solar radiation into open water and sea ice for a clear day. (This requires an estimate of the sea ice albedo for that day, the solar elevation of the sun for each hour of that day, an estimate of the open ocean water albedo each hour at each solar elevation angle, and an estimate of the atmosphere’s clarity that day, and the air mass attenuating the sun’s energy each hour of that day at that latitude. )
- an estimate of the average additional heat losses each hour on that day from the open ocean and from the sea ice.
The Antarctic sea ice continues to be far above average for this time of year: rising from +23% Feb 1 to 33.4% on Feb 28. This DOES matter, because the excess Antarctic sea ice this time of year reflects significant amounts of sunlight, and this loss continues to cool the planet. A lot.”
“The Arctic sea ice remains slightly below average for this time of year at -7%.
It doesn’t matter. There is almost no sunlight hitting the Arctic sea ice at this time of year. However, losing this Arctic sea ice cools the planet now, which often leads to additional Arctic sea ice area later in the year, which can reflect more sunlight then, then – again – cooling the planet.
I appreciate Anthony’s patience in delivering this report several days after Feb 22. As an excuse, I could claim that I needed the Cryosphere to process its data for the 22nd, or to claim that I was waiting breathlessly for the Antarctic sea ice minimum to finally arrive ( Minimum looks like it happened 28 Feb, based on Cryosphere increases reported 2-3 March), but we should all be humble as we observe the planet. Its schedule does not recognize our months and days and hours.
As usual, Antarctic sea ice goes first for several reasons.
First, it is almost always ignored by the CAGW press agents because the Antarctic sea ice reflects badly on several of their predictions about the effects of CO2 in particular and global warming in general. As observers of the global warming debate, you need to know what is happening all over, not just what the press agents want you to know, and what they don’t want you to know.
We will continue to show through the next few months just how much more important the Antarctic sea ice area actually is to the world’s heat balance: The much-hyped Arctic amplification is a very real effect. But it does NOT only occur in the limited area of the Arctic (where sea ice has been receding for several decades) but around the unlimited seas and ever-increasing sea ice surrounding the Antarctica. Down south, where the sun is always higher in the sky and the solar energy reflected back into space much greater, sea ice area really does matter.
Up north? Not so much 9 months of the year.
22 February 2015, Day-of-Year (DOY) = 053
Antarctic Sea Ice Area (SIA)
The Antarctic sea ice continued to melt through February as sea ice area decreased towards its usual its summer minimum. The Antarctic sea ice anomaly remained positive all month (more sea ice than “normal” for every day in February. The Antarctic sea ice anomaly itself decreased during the month, even though the percent of excess sea ice increased. At 0.618 Mkm^2 on 22 Feb, this “excess” sea ice is now represents a reflecting surface about half the size of Hudson’s Bay, at a latitude slightly further north than Hudson’s Bay.
The Antarctic sea ice has been more than 2 standard deviations above normal for almost every day of the past 2-1/2 years now, and February 2015 only continues that trend towards more sea ice.
SIA 1979-2008, DOY 53, = 1.874 Mkm^2, Average area this date
SIA 2015, DOY 53, = 2.492 Mkm^2, Actual area this date
SIA Anomaly, 2015, DOY 53 = 0.618 Mkm^2, Anomaly this date
Percent increase of Antarctic SIA = 33.0% more Antarctic sea ice than normal for this date
Today’s total Antarctic Ice = 14.0 + 1.5 + 2.492 = 18.0 Mkm^2.
The edge of the Antarctic sea ice is at latitude -68.3 south, slightly closer to the South Pole than the Antarctic Circle at -66.5 south latitude.
(Antarctica’s ice now covers a total area of 18.0 Mkm^2 = 14.0 mkm^2 of continental land ice + 1.5 Mkm^2 of permanent shelf ice plus 2.5 Mkm^2 of total sea ice.) Today’s Antarctic sea ice area represents Antarctica’s annual minimum area.
General Observations: The Antarctic sea ice completed its annual retreat towards the minimum sea ice area in 27-28 February, DOY = 57-58. This year’s minimum was no single sharp “point” but rather a slow flattening of the sea ice area over the last 13 days. You can never predict everything about the sea ice, but it is certainly expected to continue growing from now (2 March) through September’s maximum of 16+ million sq kilometers.
Below, the 1979-2010 avearge Antarctcic sea ice measurements are in green, this year’s actual measurements are in red. The Antarctic sea ice area anomalies are below in blue.
The remaining sea ice tends to be very close to the Antarctic land mass. The large open area (polynaya) in the Ross Sea region in January expanded somewhat, but the “ice island” offshore remained intact. This open area between the edge of the sea ice and the Antarctic continent mass is somewhat unusual, but the open water is expected to re-freeze shortly as air temperatures continue to decline. Most of the time in most years, the Antarctic sea ice lies right up close to the coastline, with the sea ice touching the coast (grounded on the beaches) called “fast ice”. (It is held fast by the land.)
Antarctic Sunlight, DOY = 53.
Solar radiation at Top of Atmosphere (TOA) = 1390 watt/m^2 this date (whole earth exposure) based on a yearly average TSI = 1362 watts/m^2. As it always does, solar radiation at TOA will continue to decrease from its yearly maximum of 1407 watts/m^2 on January 5 to its yearly minimum of 1315 watts/m^2 July 5. As far as the total planet heat balance goes, this means each day-of-year later means the sea ice at each pole will be able to reflect less and less between now and July 5.
Declination Angle on Feb 22 was = -0.183 radians/-10.48 degrees, Tau (the Day Angle) = 0.90
We are still in the Antarctic summer, but February represents late summer – compare it to early August up north. (Australian and South African readers do not need a summer-winter conversion table.)
At the edge of the Antarctic sea ice, at -68.0 latitude, sunrise occurred before 05:00 AM on Feb 22, sunset was 14 hours later after 19:00 PM.
At noon, at -68.0 latitude, air mass = 1.867; direct sunlight on a perpendicular surface = 813 watts/m^2 (Direct radiation on Feb 22 is down from January 22 due to increased air mass (greater attenuation), lower TOA radiation, and a slightly higher latitude of the sea ice edge. All as expected, since Feb 22 is later in the solar year, is right near the point of the annual minimum point for Antarctic sea ice, and has fewer hours of sunlight.)
At noon today, peak radiation on the sea surface = 434 watts/m^2 at a 32.3 solar elevation angle
At noon today under clear skies, the Antarctic Sea Ice albedo = 0.750: of the 434 watts hitting every sq meter of “excess” sea ice, 109 watts are absorbed, and 326 watts are reflected into space.
At noon today under clear skies at 32.3 SEA, the Open ocean albedo = 0.069: of the 434 watts hitting open ocean at the sea ice edge, 404 would be absorbed, and only 30 watts reflected.
Today, this day of year, from each and every “excess” meter of Antarctic sea ice, you can see that an “excess” of 294 watts/m^2 are reflected back into space (326 watts/m^2 – 30 watts/m^, clear day, at noon).
Well, “sunlight” occurs for 14 of the 24 hours down south at latitude -68.0 today, so it’s better to total the 14 hours that the sun is above the horizon. (We’ll compare this value later to what little sunlight is available up north.)
|DIR_Rad Horiz.||Hour||DIR Ocean Albedo||Dir Ocean Absorbed||Dir Ocean Reflected||Dir Ice Absorbed||Dir Ice Reflected|
So, over 24 hours, 2186 more watts/m^2 were reflected from each sq meter of “excess” Antarctic sea ice at -68.0 latitude on Feb 22 2015.
Arctic Sea Ice Area (SIA)
22 February 2015, Day-of-Year (DOY) = 53
The Arctic sea ice continues to slowly expand towards its spring maximum in late March. As expected, even as every individual day grows longer after the winter solstice on Dec 22, the Arctic continues to lose heat into space. This heat loss is seen as an increase every day in the Arctic sea ice area.
The sun rises earlier each morning, the sun sets a little later each afternoon +> Again, both as must happen as we approach the spring equinox March 22 when both north and south poles get an equal 12 hours of sunlight, and 12 hours of darkness.
Today’s Arctic sea ice anomaly remains negative at -0.979 Mkm^2. This continues its decade long negative value, and this value continues the steady negative sea ice anomaly started in early 2013 and continued through all of 2014. However, today’s anomaly is significantly smaller than both 2007 and 2012’s record low sea ice anomaly, and it represents an increase in Arctic sea ice area since 2005. Today’s Arctic sea ice anomaly remains within 2 standard deviations of the 1979-2008 mean, and that continues a trend begun in 2013 and continued through most the days since.
Today’s Arctic sea ice anomaly is obviously negative, and represents an area of “lost sea ice” roughly 81% the size of Hudson’s Bay’s 1.2 Mkm^2.
From Cryosphere (the Arctic Climate Research at the University of Illinois) for Feb 22, 2015:
SIA 1979-2008 Average, = 14.005 Mkm^2, (Average area this date)
SIA 2015, DOY 53 Actual Area = 13.027 Mkm^2, (Actual area this date)
SIA Anomaly, 2015, DOY 53 = -0.979 Mkm^2, (Anomaly this date)
Percent of Arctic SIA = only 7.0 % less Arctic sea ice than normal for this date
Total Arctic Sea Ice Area = 13.027 Mkm^2
The edge of the Arctic sea ice lies approximately at latitude 71.6 north, well north of the Arctic Circle at latitude 66.5. (This assumes a circular Arctic sea ice cap, centered at the north pole. The actual Arctic sea ice is only roughly circular, and its geometric center lies closer to the Canadian coast than to the Russian coast.)
Arctic Sunlight, DOY = 53.
Solar radiation at Top of Atmosphere (TOA) = 1390 watt/m^2, (same as Antarctica)
Declination Angle on Feb 22 was = -0.183 radians/-10.48 degrees, Tau (the Day Angle) = 0.90
At the edge of the Arctic sea ice, at latitude 72.0 north, the sun pokes its head above the horizon a little before 09:00 AM, and sets 6 hours later a little after 15:00 PM.
At noon today, 22 Feb, air mass = 6.780, solar elevation angle = 8.1 degrees
At noon today, 22 Feb, peak radiation on the sea surface = 28 watts/m^2 at only 8.1 degrees solar elevation angle.
At noon today, 22 Feb, the average Arctic sea ice albedo = 0.830, (Arctic sea ice albedo is still at its winter maximum) but almost no energy is available: 5 watts would be absorbed, 23 would be reflected.
At noon today, 22 Feb, at 8.1 degrees SEA, the open ocean albedo = 0.419 (Pegau & Paulsen, 2006), so 16 watts/m^2 would be absorbed, 12 watts/m^2 would be reflected.
The Arctic sea ice anomaly is negative (meaning sea ice has been lost from its 1979-2010 average), so open water dominates the reflection exchange: At noon on Feb 22, each sq meter of open ocean absorbed 16 – 5 watts/m^2 => the Arctic Ocean absorbed an additional 11 watts/m^2.
Over the 24 hour day, this was a total of 34 watts/m^2. (The math, if anybody is interested: if open ocean, the water absorbed 4+12+16+12+4 watts = 50 watts/m^2. If sea ice were present, the ice would have absorbed 2+4+5+4+2 = 16 watts/m^2. The difference = 50 – 16 = 34 watts/m^2.)
Today, this day of year, for every “lost” square meter of sea ice, the open Arctic ocean loses more energy from 24 hours of increased losses (increased long wave radiation from the open ocean water, from increased convection and conduction up to the sea surface, and from increased evaporation) than it gains from a few hours of increased absorption in the open Arctic Ocean. In all cases, at this latitude at all hours of the day, more energy is lost from the open Arctic Ocean water than from ice-covered Arctic waters.
Today, this day of year, less Arctic sea ice = more heat loss from the Arctic ocean.
Net Planetary Sea Ice Heat Balance (at noon, this day of year).
Arctic sea ice area anomaly x net solar energy absorbed/m^2 – Antarctic sea ice anomaly x net solar energy reflected /m^2
Over a 24 hour day on Feb 22 2015, the net effect of today’s sea ice was
.979 Mkm^2 x 34.0 watts/m^2 – 0.618 Mkm^2 x 2186 watts/m^2 = -1317.6 MWatts reflected back into space, thus cooling the planet.