Jennifer Marohasy

a forum for the discussion of issues concerning the natural environment

sea level change

Supernovae Affecting Global Climate and Ocean Biodiversity and Productivity

By

REMEMBER Henrick Svensmark and Eigil Friis-Christensen and cosmic ray theory [1]: the idea from these Danish physicists and climate scientists that global climate may be mediated by changes in the flux of galactic cosmic rays because cosmic ray are conducive to cloud formation?

Henrik Svensmark has just published a new paper: now available for download in full from the front page of the Royal Astronomical Society’s website [2] and the subject of a detailed post by Anthony Watt [3].

The new paper focuses on local supernova rates (rates of explosions of large stars) and suggests that high rates of explosion could coincide with colder conditions on planet earth. The paper draws a correlation between long-term changes in sea-level and supernova rates and marine biodiversity and productivity over the last 510 million years.

Dr Svensmark goes as far as to hypothesis that the biodiversity and primary productivity of the oceans depends on the supernova rate; somewhat counter intuitively that glacial conditions will result in increased primary productivity.

“A simple working hypothesis, suggested by carbon-isotope data for the past 4 Gyr (Svensmark 2006a), is that primary productivity increases in glacial conditions, perhaps because of better nutrient supplies, caused by a more vigorous mixing in the oceans during cold conditions. This hypothesis would predict the following.

(i) 
A drawdown of CO2 from the environment in glacial conditions. Since organic productivity consumes CO2, there should be an impact on the levels of atmospheric and oceanic CO2. High productivity draws down CO2, until ultimately the productivity rise is halted not only by exhaustion of nutrients, but also by the scarcity of CO2, which should prevent a total loss of environmental CO2. Conversely, low productivity should result in an accumulation of underemployed CO2.

(ii) 
Due to the increased organic productivity, an increase in the heavy stable isotope of carbon, 13C, is expected in the oceans during glacial conditions.

I’m fascinated.  But not convinced.

H/T Neville.

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[1] Cosmic Rays, Clouds and Climate (Part 1) https://jennifermarohasy.com.dev.internet-thinking.com.au/2008/04/cosmic-rays-clouds-and-climate-part-1/

[2] Henrick Svensmark 2012. Evidence of nearby supernovae affecting life on Earth. Monthly Notices of the Royal Astronomical Society.
Links here:
http://www.ras.org.uk/news-and-press/219-news-2012/2117-did-exploding-stars-help-life-on-earth-to-thrive
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2966.2012.20953.x/full

[3] Svensmark’s Cosmic Jackpot: Evidence of nearby supernovae affecting life on Earth at Watts Up With That? http://wattsupwiththat.com/2012/04/24/svensmarks-cosmic-jackpot-evidence-of-nearby-supernovae-affecting-life-on-earth/#more-61941

Beach Mounds Not Middens

By

WALKING on the beach this afternoon I took some photographs of beach mounds. I’m referring to piles of shells and pebbles regularly positioned between, and parallel to, the high and low tide marks.

Are these beach mounds a consequence of the ebb tide dragging the sand away from the shells and pebbles or a consequence of swash action dropping shells and pebbles?

During periods of global sea level rise there is typically an overall increase in the amount of sand deposited along a beach.

But a small change in the relative strength of the ebb tide can presumably significantly change the patterns we see on beaches. How different would our beaches look if global sea levels were falling rapidly?

Large mounds dominated by a single shell species near Weipa on Cape York Peninsula (North Queensland) were once considered aboriginal middens but may in fact have been beach mounds. According to Tim Stone from the Australian National University they are not middens by rather a natural consequence of local chenier plain development.[1]

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[1] Shell mound formation in coastal northern Australia by Tim Stone
Marine Geology, Volume 129: 77-100. 1995

Abstract
Shell mounds are late Holocene deposits typically dominated by a single shell species. In northern Australia these mounds are associated with prograding coastal plains. The largest and most numerous are at Weipa on Cape York Peninsula. Archaeologists claim that these mounds were formed by generations of shellfishing Aborigines. This hypothesis is false because most of the shells from the type-site are of a similar radiocarbon age. Mapping and augering of two contrasting shell mound environments along the Mission River at Weipa demonstrates that mound formation is a natural consequence of local chenier plain development. This is supported by shell ages from across the Weipa landscape. The shell mounds at Prumanung originated as a coarse shell berm. The large mounds on the Uningan plain originated as small shell cheniers. The only reasonable explanation for the transformation of these natural shell deposits into tall, steep-sided mounds is the mound-building behaviour of the Orange-footed Scrubfowl Megapodius reinwardt. Similar mounds composed predominantly of sand and gravel are also present at these localities. The strong likelihood that the shell mounds are natural shell deposits raises serious questions about basic principles of shell midden archaeology. New methods for distinguishing between cultural and natural shell deposits are needed.

http://www.sciencedirect.com/science/article/pii/0025322795001018