The article, Kelp genes reveal effects of subantarctic sea ice during the Last Glacial Maximum, describes an experiment designed to measure the extent of sea ice in the Southern Hemisphere during the Last Glacial Maximum (LGM). Prior to this study, palaeogeographers had had yet to decisively determine the extent of sea ice in the southern hemisphere during the LGM, so this experiment greatly contributed to the progress of the palaeogeographic field. The authors of this article also notably pioneered a new method of study in this field; they were the first palaeogeographers to examine modern genetic data in order to draw conclusions about the past conditions and climate of the southern hemisphere (Fogarty, 2009).
The authors used mitochondrial and chloroplast genetic markers (COI; rbcL) to genetically examine 300 kelp samples from 45 various locations about Southern Ocean localities. They then used these results to approximate how long the kelp has been in that area; if the kelp displayed genetic homogeneity then it suggested that the kept recently colonized the area, and if the kept did not then it suggested that that population of kelp has been there for a comparatively longer period of time (Fraser et al., 2009). Since the D. antarctica cannot survive ice scour, it is inferred that the areas in which the kelp seem to have recently colonized were affected by ice scour during the LGM. As a result of the experiment, the authors found that their data suggested that the ice cover during the LGM spanned a much larger area than previously assumed.
In the article, the authors provide a diagram containing the results of their genetic characterization of the kelp on page 2. The figures are organized into a phylogenetic tree. The purpose...
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...nes Reveal Effects of Subantarctic Sea Ice during the Last Glacial Maximum." Proceedings of the National Academy of Sciences 106.9 (2009): 3249-253. Print.
Fraser, Ceridwen I., Martin Thiel, Hamish G. Spencer, and Jonathan M. Waters. "Contemporary Habitat Discontinuity and Historic Glacial Ice Drive Genetic Divergence in Chilean Kelp." BMC Evolutionary Biology 10.1 (2010): 203. Print.
Hinojosa, Iván A., Matías Pizarro, Marcel Ramos, and Martin Thiel. "Spatial and Temporal Distribution of Floating Kelp in the Channels and Fjords of Southern Chile." Estuarine, Coastal and Shelf Science 87.3 (2010): 367-77. Print.
Wagstaff, SJ, I. Breitweiser, and M. Ito. "EVOLUTION AND BIOGEOGRAPHY OF PLEUROPHYLLUM (ASTEREAE, ASTERACEAE), A SMALL GENUS OF MEGAHERBS ENDEMIC TO THE SUBANTARCTIC ISLANDS." AMERICAN JOURNAL OF BOTANY 98.1 (2011). Web of Science. Web. 13 Nov. 2011.
For the original analysis, the corrected pairwise distance will be calculated using the Jukes–Cantor and the Maximum Composite Likelihood Model. The Jukes–Cantor model assumes that the rate of nucleotide substitution or all nucleotides (C, A, T and G) are equal, that nucleotide frequencies are equal, that there is an equal rate of substitution among sites, and does not correct for the lower rate of transversion substitutes in comparison to transitional substitutions (Jukes and Cantor, 1969). The Maximum Composite Likelihood takes into account the phylogenic relationship between sequences, using the sum of the log likelihoods of the bases as the composite likelihood. Both pair wise distances and substitution parameters are estimated using the Maximum Composite Likelihood (Tamura et al. 2004). Both models should yield different maximum sequence divergence and average divergence that can then be compared to the original paper. With sequence divergence data, the temporal origin of the genus can be identified. The two alternate models to the Kimura-2 parameter will be analyzed to discuss which methods yield results closest to the expected time origin of the genus
Americas by 14,000 ago” (O’Brien 12), after large portions of North America encountered the last ice age, which
...Clague, John J., Luckman, Brian H., Wiles, Gregory C. “Tree-Ring Dating of the Nineteenth-Century Advance of Brady Glacier and the Evolution of Two Ice- Marginal Lakes, Alaska.” The Holocene 21.4 (2001): 641-649. Sage Journals. Web. 9. Feb. 2014.
The Web. 28 July 2011. http://redpath-museum.mcgill.ca/Qbp/3.Conservation/impacts.htm>. Interaction with kelp & sea otters. asnailsodyssey.com.
The earth is about four billion years old, within the span of these four billion years; the earth has become accustomed to various transitions and dissimilar geological and environmental permutations. The Ice age period has been the subject of much debate regarding these various transitions. As the rate at which geological disasters on earth continue to intensify we begin to ask ourselves whether it is possible for an ice age to spontaneously occur overnight. Nonetheless, In order for such a disaster to persist, massive improbable geological events would have to occur and graft coherently which is evidently and scientifically impossible. The notion that an ice age can occur overnight is implausible for the reason being that: Global warming is on a evidential rise , chances of catastrophic volcanic activity as deteriorated and the earth's orbit is at a period of solar radiation absorption.
The Little Ice Age is the name for the period of cooling spanning from 1400 to 1900 c.e. that took place after the Medieval Warm Period. Scientists believe that solar minimums and reversals in the Northern Atlantic Oscillation, a large atmospheric-circulation system that affects weather in the North Atlantic area including Europe, drove these changes (Encyclopedia Britannica, 2014). It is often assumed that the Little Ice Age had a global impact. However, in 2001, the Intergovernmental Panel on Climate Change put forth in a climate assessment report that though there were glacial increases in other parts of the world, they were not synchronous with the glacia...
The Pleistocene epoch is a well-known time period thanks to the glorification of now extinct megafauna as well as the proximity to our current epoch. Through the rapid climate changes and glaciation that occurred many times during this epoch, the fauna
Both Allen (2008) and Hoffman (1998) then thought that the glaciation ended fast due to very high levels of carbon dioxide. According to Hoffman (1998) the carbon dioxide levels got higher because of release ...
... might not develop back to normal conditions, in which case the demise of the Greenland ice sheet and the associated sea-level rise might be irreversible. For this reason, the Greenland ice sheet is often described as a relict ice mass. It survived the current Holocene interglacial solely because it creates its own cold surface-climate because of its elevation. The last time Greenland temperatures were several degrees higher than today was the last interglacial 125,000 years ago. Ice core evidence for a smaller ice sheet is consistent with the observation that sea level then was several meters higher than today. At that time, the ice sheet did not disappear completely, probably because the warming was not strong enough and did not last long enough. The ice sheet was probably saved from extinction by the onset of the last glacial period several thousand years later.
Amos, Jonathan. “Deep Ice tells Long Climate Story.” BBC News. BBC News. 9/4/2006. Web. 4 Apr. 2014.
Globally, climate change is regarded as both an urgent as well as serious issue (Stern, 2006). Defined as the lasting and significant change in the statistical distribution of the patterns of weather over periods that range between years to decades, climate change is believed to be a result of the human activities which have lead to global warming over the years (Sagan& Chyba1997). Other prospective contributors to climate change include biotic processes, solar radiation variations, volcanic eruptions and plate tectonics. Scientists continue to work actively with the aim of understanding the past as well as the future climate through observations and the use of theoretical models. A climate record has been assembled through the deep extension into the past of the earth .This assembly continues to be built up based on evidence that is geological in nature such as borehole temperature profiles, faunal and floral records, glacial process among others.
Just a couple weeks ago, we were complaining how winter was so cold and how it would never end in Canada; but imagine living in the glacial period, where there was a time when glaciers, large masses of ice, covered a huge portion of the Earth’s surface. Studies show that the polar ice caps, as we know them today used to cover approximately 30% of the Earth during our last Ice Age. The Earth remained in this state for thousands and thousands of years. Cold, right? According to geologists, there have been an approximate total of 5 major ice ages. They began appearing roughly 2, 300, 000 years ago, up until the most recent one, approximately 10,000 years ago; it was the ice age period/glacial period, and that’s was exactly what happened. Ice Ages are points in time when the temperatures around the world, including the atmosphere and the surface of the Earth, were cold consistently for a span of over multiple thousand years. Unlike the average temperature of 220C we have now, the ice ages were much colder, having an average of approximately 50C.
The purpose of this paper is to investigate whether global warming could affect the thermohaline circulation cycle (THC) significantly enough that it could even shut it down and thus cause a shift in the climate of Europe severe enough to cause another Little Ice Age. To answer the question about whether global warming could cause another ice age, I have divided this paper into segments. The first will explain what the thermohaline circulation cycle is. Next, I will look at the last interglacial period and observe what the conditions were like especially in respect to the THC. I will look at how the last interglacial led to the last great Ice Age, and the sudden demise of that Ice Age, as well as the nearly equally sudden cooling that occurred in the Younger Dryas about 12,000 years ago before the warming resumed in earnest shortly thereafter. In the final part of this paper I will look at two different predictions of what could happen as a result of the melting of the North Atlantic region's ice sheets with respect to the THC and how it could affect the regional climate in Europe.
Tripati, Aradhna. (2009). Coupling of CO2 and Ice Sheet Stability Over Major Climate Transitions of the Last 20 Million Years. Science. http://www.sciencemag.org/content/326/5958/1394.abstract