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Antarctica gaining Ice Mass (balance*) — and is not extraordinary compared to 800 years of data

Posted By Joanne Nova On April 16, 2013 @ 5:58 pm In Global Warming | Comments Disabled

It’s difficult to say anything for sure about Antarctica because the weather is so variable. Bumper snow one year, not so much the next. (Noise and uncertainty is large). But 800 years of ice cores spread across Antarctica shows the Surface Mass Balance (SMB) is more likely to have been increasing over the last century. (Which fits with what Zwally et al found in 2012 with ICESAT satellite data).

Note the correlation of the smoothed average of the SMB (orange line) with Total Solar Irradiance (green line).

Antarctic Ice has been increasing for the last half century, and over 800 years it correlates with solar radiation. TSI: Total Solar Irradiance (Click to enlarge)  Fig. 5. (A) Mean normalised stacked SMB anomaly time series at the continental scale, calculated as described in the text (black line with positive and negative values filled in with red and blue contours, respectively) and the 40-yr central running average smoothing (orange line). The green line represents the normalised TSI anomalies, and the corresponding ±1 uncertainties are indicated by the green vertical bars.

H/t: HockeySchtick and Jaymez

A paper published today in The Cryosphere finds Antarctica has been gaining surface ice and snow accumulation over the past 150+ years, and finds acceleration in some areas noting, “a clear increase in accumulation of more than 10% has occurred in high Surface Mass Balance coastal regions and over the highest part of the East Antarctic ice divide since the 1960s.” 

They used 67 firn/ice core records to reconstruct the last 800 years.

From this paper we can see:

  1. Over 800 years, Antarctic ice changes all the time, but current rates of change are not unusual. The surface mass balance (SMB) “changes over most of Antarctica are statistically negligible.” The  “current SMB is not exceptionally high compared to the last 800 yr.”
  2. The times with highest accumulation (1370s and 1610s) match records of solar radiation.
  3. Since 1960 the ice and snow accumulation has increased by 10% in high SMB coastal regions and over the highest part of the East Antarctic divide.

 

Fig. 4. Mean normalised anomalies of the annually resolved SMB time series at continental and regional scales obtained from the time ice core dataset, as described in the text. (A) Number of records from each year in the period from 1200 to 2000 used to calculate the continental (black line, left y-axis), WILKES, DML, and WAIS stacked records (black, blue, green and red lines, respectively, right y-axis). (B) Mean normalised anomalies of the SMB time series at the continental scale. (C) The DML mean normalised anomalies stacked record. (D) The WAIS mean normalised anomalies stacked record. (E) The WAIS mean normalised anomalies stacked record along with the ±1 uncertainty standard deviation (grey-filled contour around each stacked record). The blue- and redfilled rectangles represent periods with negative and positive SMBs at the continental scale, respectively, as described in the text.

 Solar irradiance seems to matter to Antarctica

How curious:

Eight hundred years of stacked records of the SMB mimic the total solar irradiance during the 13th and 18th centuries. The link between those two variables is probably indirect and linked to a teleconnection in atmospheric circulation that forces complex feedback between the tropical Pacific and Antarctica via the generation and propagation of a large-scale atmospheric wave train.

As far as we can tell, the Antarctic Ice Sheet (AIS) is growing

The Surface Mass Balance appears to be growing at 2100Gt/year (though this is much higher than the ICESAT satellite estimates of Zwally which estimate a net gain of 49Gt/year.)

[UPDATE: ManicBeanCounter, pointed out that if 2100Gt was being shifted from the ocean to the land, it would reduce oceans by 5mm annually. An improbable figure! DumbScientist below helpfully points out that Zwally is using Total Mass Balance, which is different to Surface Mass Balance. The SMB figure involves "precipitation, evaporation and snowdrift physics" but not glacier run-off. Thanks to both readers.]

“The SMB of the grounded AIS is approximately 2100 Gt yr−1, with a large interannual variability. Those changes can be as large as 300 Gt yr−1 and represent approximately 6% of the 1989–2009 average (Van den Broeke et al., 2011).”

Climate models predict that snow and ice ought to accumulate over Antarctica and that this will help slow down sea-level rise. Maybe the models are right on this, but there’s no evidence in this data that the current accumulation is different to natural cycles.

The summer melt might be faster at the moment, but the accumulation rate is also seemingly at the higher end. If climate scientists want to blame increased CO2 emissions in the last 150 years for the increased ice mass (snow accumulation) and faster summer melt, then how do they explain all the other rises and falls over the last 800 years? Look at the graph below and ponder that all the bumps and falls were natural apparently but that last bump — we’re 90% sure it’s caused by coal power stations.

 

(A) See the copy at the top of this post. (B) Running correlations in 100-, 200-, and 300- yr time windows (red, green, and blue solid lines, respectively) between the normalised TSI anomaly and the continental accumulation record, smoothed as described in the text. The red, green, and blue dashed lines represent the threshold values corresponding to the 95% statistically significant level based on a two-tailed Student t-test (100-, 200-, and 300-yr time running windows, respectively). The filled grey areas represent the Wolf, Sp¨orer, and Maunder minimums in solar activity.

The full paper is here: The Cryosphere, 7, 303-319, 2013

REFERENCE

Frezzotti, M., Scarchilli, C., Becagli, S., Proposito, M., and Urbini S. (2013)  A synthesis of the Antarctic surface mass balance during the last 800 yr The Cryosphere, 7, 303-319,  doi:10.5194/tc-7-303-2013   Final Paper (PDF)   Discussion Paper (TCD)

Zwally, H. Jay; Li, Jun; Robbins, John; Saba, Jack L.; Yi, Donghui; Brenner, Anita; Bromwich, David (2012) Mass Gains of the Antarctic Ice Sheet Exceed Losses Click to View PDF File [PDF Size: 256 KB] [ WUWT discussion]

 

Seee WUWT GRACE’s warts – new peer reviewed paper suggests errors and adjustments may be large

*”Balance” added to the title to clarify

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