Scientific Information Posting No. 18

LARGER PHOTOGRAPHS AVAILABLE

Several folks have asked if there are larger versions of the photographs included in Scientific Post No. 17 available(?). Yes, there are.

Bob Christiansen emplaced a link near the bottom of Post No. 17 which, if you click on it as instructed, will lead you to a selection of enlarged images for easier viewing.

Scientific Information Posting No. 17

Splitting the Cores

Sorry to offer this posting a little out of order. With all the flurry of follow-up investigation of material sampled from the core, we neglected to offer a glimpse of the core splitting session itself.

A group of us met at Plymouth State University on Saturday, May 3 to begin the process. To start with, we retrieved the deeper core segments from the 4 C coldroom where they had been stored since the original sampling date. The foil and cling wrap covering of the core segment was carefully unwrapped and details regarding its appearance and texture were noted.




Then the segment was split longitudinally into halves to reveal the interior material.
Having laid a tape measure along side it, we photo-documented the segment and, using a standard soil color chart, we noted its appearance before subtle color tones could change as these sediments were exposed to air for the first time in thousands of years.



Most core segments (such as the one below) have a brownish-gray appearance produced by the remains of biologically produced organic materials (plant, animal, and microorganismal remains) mixed with inorganic mineral materials. Brownish organic deposits in lake bottoms is known as "gyttja" (a Swedish word, pronounced "yit-yah").



Then at specific depth intervals along the core, subsamples of sediment were extracted for detailed analysis. All subsamples were removed from one side of the split core so that the opposite side could be stored intact for archival purposes. Subsamples taken






will be examined for the remains of midge larvae (or chironomids – useful in reconstructing past temperatures), pollen (useful in reconstructing a picture of changes in the surrounding landscape), the degree of sediment compaction (useful in analyzing the impact of overlying geological forces) and organic content (using a "loss on ignition" or LOI technique – useful in characterizing changes in overall biological productivity over time). The significance of each of these studies will be presented as results become available in the months ahead.

As we had seen in the field, in the 11th segment we collected, a dramatic change in appearance was noted between the brownish (gyttja) sediments and the gray mineral silts that apparently lack such organics. The illustration below shows that transition point between 23 and 24 meters below the Pond surface. A subsample of sediment from this transition point was used for dating purposes (described in Scientific Posting 16).

Click on this image for short slideshow of larger images!

Lee Pollock

WHERE ARE THE PICTURES?

Several people have recently asked where/how to find the pictures and slide show taken during the actual drilling out on the ice last March. It's easy.

Simply scroll all the way down to the last the postings on the blog as it exists today and then click on "Older Postings" in the lower right-hand corner. Once you're into these older postings, scroll down until you reach the post that includes the photos/slide show.

Scientific Information Posting No. 16

WHEN DID THE GLACIER LEAVE THE BIG PEA PORRIDGE POND BASIN?

Well folks, sorry for the long delay in getting information to you here on the blog. Since we finished the first round of sample splitting and sampling in early May, we've been awaiting laboratory results to report and to use to plan the next steps in our investigation. Now, the first of these results is "in", and here it is - the one you've all been waiting for.

The Carbon-14 (AMS) age of the likely oldest organic material at the bottom of the Pond is 12,150 +/- 50 years. If you correct this to calender years, it lies between 13,910 and 14,100 years, or just about 14,000 years.

This is the age of the first organic material to be deposited on the surface of the very compact silt and clay basin left by the glacier when it departed, and it represents the starting date for the rest of the paleoecological history of the Pond our investigation will gradually reveal over the coming months. This date represents the point in time when the local climate had warmed sufficiently from very cold glacial conditions so that the first types of pond vegetation and critters could sustain themselves in and around the Pond. Our investigation from here will document just what these life forms were and how they changed over time to the present. Suffice to say for now, though, you can rely on the fact that we are all part of a history here on the Pond that started 14,000 years ago.

Bear in mind that this date is just the first in what we expect will be a long line of such information (along with more professional analyses) that will come out of our investigations over the next several months. Please feel free to send us your comments and questions via the Commenting Feature here on the blog. We'd enjoy the chance to talk with you about these exciting developments.

Also, keep on eye here for "social postings" about the one or more of information meetings we hope to conduct this summer on the Pond to describe what we're finding and discuss what it all means about the paleoclimate and past ecology of the Pond's basin. As things proceed along with our work and we learn more and more about what went on here in the past 14,000 years, "the Pond will never be the same" to any of us.

More later and as it becomes available...

Scientific Information Posting No. 15

Follow-up DO-Temperature Profile

Earlier, we posted a temperature-dissolved oxygen profile for Big Pea Porridge Pond taken March 30, 2008. Its purpose was to show:

1) the winter temperature profile, with densest (4 C) water filling the lake bottom and underlying colder (therefore less dense) water beneath the ice-covered surface. With less dense water "capping off" more dense deep water, the water column is stabilized, i.e., little vertical mixing or replenishment of deep waters occurs in winter. Also, ice cover prevents wind (the major force behind lake water mixing) from accessing the water surface. Winter stagnation of the column results.

2) the dissolved oxygen curve dropping off with depth. Loss of oxygen in deeper waters is primarily the result of the bacterial/fungal decomposition of organic (i.e., biologically derived) matter that has sunk to accumulate on the bottom. Without circulation to replenish lost oxygen, the extent of oxygen loss is a rough measure of how much organic matter is produced in the lake – in other words, its level of productivity.

As warmth returns in spring and the ice melts, the < 4 C surface waters heat up to match the 4 C deep waters. At that point, temperatures and therefore density of waters within the entire water column are equal. As a result, the water column loses its "stability". As the wind blows across surface waters, pushing them toward the leeward side of the lake, surface waters are driven downward, while elsewhere in matching volume, the lake deep waters are forced to the surface. This creates a "turnover" during which the water column becomes uniformly mixed. Temperatures and dissolved oxygen levels (replenished as oxygen-stripped deeper waters mix to the surface and make atmospheric contact) are equal top to bottom.

This process is the "spring turnover". Full lake vertical mixing like this returns to sun-lit surface waters the nutrients that were freed during the winter as decomposers worked over the organic matter there. These vital nutrients were trapped until the turnover by the stagnant winter water column. With sunlight and nutrients finally available in surface waters, the single-celled and colonial phytoplankton (the plant component of the plankton community – algae, diatoms, dinoflagellates, bluegreen bacteria, etc.) – can surge into photosynthetic action, producing a peak in lake's annual productivity known as the "spring bloom".

The graph below shows the temperature-dissolved oxygen profile observed on May 9, 2008 at the "deep spot" in Big Pea Porridge Pond. If you tip your head 90 degrees to the left, you can see the results from top (left) to bottom. As you will see, we missed catching the turn-over period exactly. While the water column is still pretty uniform with regard to dissolved oxygen levels, the temperature profile is no longer uniform. Understandably, the top 3 meters of surface waters are capturing more heat than deeper waters. By doing that, the warming surface waters, referred to as the "epilimnion", are also becoming progressive less dense than the deeper, cold waters of the "hypolimnion". (There is an inverse relationship between temperature and density – the higher the temperature, the lower the density of water). The intermediate zone including the steep temperature gradient separating these two layers, e.g., between 2-3 meters on this graph, forms the "metalimnion" or "thermocline". As the temperature-density contrast builds between epilimnion and hypolimnion waters, the stability of the water column builds. Deeper, colder, denser waters resist wind-driven vertical mixing of warmed surface waters. The whole lake is no longer involved in mixing – just the wind-driven, warmer epilimnion waters continue to circulate. As the vertical depth of mixing becomes more limited, lower-density, surface epilimnion waters become warmer and warmer, and the stability of the water column increases. This leads to a summer-time stratification/stagnation of the water column that isolates deep, darker, colder hypolimnion from the sunny, warm low density epilimnion. The buildup of the summer temperature stratification will be the subject of our next temperature-dissolved oxygen profile later on in the season.



Lee

Scientific Information Posting No. 14

While not purely scientific information, this is a project follow-up note on aesthetics for residents of Big Pea Porridge Pond looking out across the melting but still nearly complete ice cover (here on April 23!). We just wanted you to know that the debris the melting ice is revealing in the general vicinity of the drilling site is NOT anything we left behind there! But it is indicative of the depth of ice & snow cover this winter that the bright red plastic milk crate and the several large blocks of wood revealed now were completely and invisibly buried there at the time of our drilling operation. Lee.

Quick update on scheduled presentations regarding the MPEP project

1. We will be included with a poster/information table display at the Climate Change Forum scheduled for 6:30-8:30 p.m. on Monday, April 28th at the Kennett High School Auditorium. At the forum, presentations from experts around the country will focus on the science as well as economic and social aspects of the climate change phenomenon, including regional and global challenges and solutions. Speakers from organizations and state agencies will provide presentations on New Hampshire’s Climate Change Action Plan, information and science related to their field of expertise, and will also answer audience questions. Call 539-1859 for more information. Hosted by the Green Mountain Conservation Group, Eagle Academy and Timberland, Inc. The public and other schools are welcome to attend this event.

2. We will also use the poster/ information table format to help represent the activities of the Tin Mountain Conservation Center at a gathering from 6:30-8:30 at Granite State College on Wednesday, May 21. We have recently formed a linkage to Tin Mountain, finding that the MPEP project has much in common with their educational mission.

3. We will present a program based on the MPEP study for the Kennett High School Environmental Club at their monthly meeting at the Tin Mountain Conservation Center on Wednesday, May 21. Contact Tin Mtn for more information: 447-6991.

4. On Tuesday, June 10, we will review the MPEP program so far, and talk about its goals as part of the Tin Mountain Conservation Center's Nature Program series. More information at Tin Mtn: 447-6991.

At each of these sessions, we hope to gather names of individuals interested in the issues raised by our project. This group will form an informal discussion "club" that will be invited to meet at the Tin Mountain Center periodically to learn about new information as analytic results become available and to help us all explore the evolving story of the post-glacial period in this area.

Lee Pollock