Antarctic Peninsula warmer in mid-Holocene
May 26th, 2006 by Warwick HughesSome interesting papers from an AGU conference.
“Mid Holocene Warmth in the Antarctic Peninsula: evidence from the Vega Drift”. So, 4000 to 7000 years ago this area was warmer than now.
Jumbo piston core NBP0003-38, a 20.53 meter core from the Vega Drift (Erebus and Terror Gulf, northeastern Antarctic Peninsula), contains a high resolution record of climate extending back ~8500 years. Lithologic and foraminiferal data presented previously document mid-Holocene conditions warmer than today. These data include increased clay concentration, higher concentrations of ice-rafted debris, and higher magnetic susceptibility below ~6000 ybp, the consequence of extensive meltwater and iceberg calving. This change in lithology is accompanied by the presence of a benthic foraminferal assemblage characteristic of the western Antarctic Peninsula, as contrasted to a lower productivity assemblage observed in the upper section of core. New diatom data confirm mid-Holocene warmth, as based on analysis of the distribution of the two varieties of the species Eucampia antarctica. They are distinguished by their symmetry, with the asymmetric E. antarctica var. antarctica characteristic of subpolar waters and the symmetric E. antarctica var. recta a polar form. Increased relative abundance of the sub-polar form occurs between ~4000-7000 ybp, overlapping and then post-dating the time interval characterized by increased ice melt. In addition, the ratio of terminal to intercalary valves was analyzed. A direct consequence of chain length, a function of the amount of growth, this ratio has been used to record oscillations in winter sea ice cover. Data from JPC38 show longest chain lengths (and least winter sea ice) from ~4000-7000 ybp, in concert with the dominance of the sub-polar form of the species. These data suggest the possibility that mid-Holocene warmth at this site was associated with the southward migration of sub-polar waters and consequently less winter sea ice.
So much for all the years of the British Antarctic Survey beating up warming trends from station data there.
Another interesting paper mentions an active undersea volcano in the area. “A Benthic Invertebrate Survey of Jun Jaegyu Volcano: An active undersea volcano in Antarctic Sound, Antarctica”.
Jun Jaegyu volcano, an Antarctic submarine volcano, was dredged in May 2004 during cruise 04-04 of the RV Laurence M. Gould to determine rock, sediment composition and marine macroinvertebrate diversity. The objectives of this study are to examine the benthic assemblages and biodiversity present on a young volcano. The volcano is located on the continental shelf of the northeastern Antarctic Peninsula, where recent changes in surface temperature and ice shelf stability have been observed. This volcano was originally swath-mapped during cruise 01-07 of the Research Vessel-Ice Breaker Nathaniel B. Palmer. During LMG04-04 we also studied the volcano using a SCUD video camera, and performed temperature surveys along the flanks and crest. Both the video and the dredge indicate a seafloor surface heavily colonized by benthic organisms. Indications of fairly recent lava flows are given by the absence of marine life on regions of the volcano.
We are looking for more data.
Posted in Climate indicators, Cryosphere | 11 Comments »
May 26th, 2006 at 5:56 pm
If Antarctica was warmer during the holocene, one wonders what the temperature was during the same period elsewhere, say the existing equatorial and temperature regions of the planet.
I sense some difficulties here for the climate people.
May 28th, 2006 at 1:26 pm
Could these lava flows be responsible for the demise of the Larsen Ice Shelf ?
May 29th, 2006 at 4:27 am
Gidday Bryn, I am trying to obtain the complete papers.
If you put the terms “iceland glacier volcano melting” into Google you get several references to volcanic activity under an icesheet on Iceland causing melting. So I suppose it is feasible that warmer water from undersea lava could rise and affect sea ice.
May 30th, 2006 at 8:21 am
Not to mention the locally lithospheric rise in temperature from a volcanic eruption.
As no one is measuring it, we have no data, and in the absence of data, no opinion.
Except for those who opine in the absence of data.
Which the media seem to report.
July 8th, 2006 at 2:41 am
I have looking at recent images of Antarctic sea ice.There seems to be a strip that is anomalously warmer east of the Antarctictic peninsula. This could indicate undersea volcanic action close to where the Larsen Ice shelf disintegrated.
July 11th, 2006 at 7:08 pm
Undersea volcano, yes. Cause of/contributor to disintegration, not definitive at least in this article and when I asked Dr. Connolley (as of post 53, in mid-APR):
www.nsf.gov/news/news_summ.jsp?cntn_id=100385&org=NSF
www.realclimate.org/index.php/archives/2006/03/significant-warming-of-the-antarctic-winter-troposphere/
July 13th, 2006 at 4:53 am
Dr Connolley, like most climatologists, stops answering emails when the questions get awkward,pleading lack of time.(He’s got plenty of time to do other things like writing posts fo Real Climate.)
My argument is simple: the Antarctic penninsula is behaving differently than the rest of the Antarctic.It is warming whilst the rest of the Antarctic is cooling.If AGW does not affect most of the Antarctic why should it affect the Antarctic peninisula. It can’t be because it sticks out like a sore thumb since the winter sea ice extends beyond it and hardly ever retreats south of the penninsula on the western side.
The penninsula is part of the so called Ring of Fire, the ring of volcanoes around the the Pacific Ocean.
I think it is incumbent on the climatologists to demonstrate to us that the AP is not affected by volcanic action not the reverse.
BTW There is a volcano under where the Larsen Ice Shelf collapsed. Google”Seal Nunataks”
July 18th, 2006 at 2:55 pm
Tom B – I would also wonder about any oddities in ocean currents which might impact only the Peninsula but not areas to the south.
July 22nd, 2006 at 11:43 am
In general the sea currents in the Ross sea circulate so as to cause a northern flow along the Antarctic Peninsula.
Shackletons ship drifted north in the pack ice off the Antarctic peninsula in 1915.
July 24th, 2006 at 4:13 am
I should have said Weddell sea not Ross sea.
July 26th, 2006 at 1:40 pm
Your characterization of the practices of Dr Connolley are mild, compared to some of his on record. To be honest, when I questioned him about, I expected an authoritarian response — his acknowledgement of uncertainty, surprised me. Perhaps he is mellowing a bit.
Re: theory — was thinking similarly, especially after the widespread press certainty of AGW causing the breakaway.
sidebar re: Shackleton,currents, wind — still amazes me that they drifted in pack ice, for ~1000 miles from Jan-Nov’05, before the ship sunk, and ~500 mi more in 5 months, before launching boats to Elephant Island. And all this was only the 6:00-10:00 portion of their clockwise trip from/to S. Georgia