Sediments that tell stories: Patagonian ice sheet sediment cores reveal millennia of glacier rise and fall
February 13, 2014 image of the Southern Patagonian Ice Field, taken from the International Space Station. (Expedition 38 Crew/ nasa)
A team of researchers embarked on their journey around frigid Patagonia, crossing waterways to fjords surrounded by snow and ice. They withstood freezing temperatures throughout their journey, all in order to extract the perfect sedimentary core: the key to the glacier history of the southern Patagonian Ice Field.In the course of their research, recently published in Quaternary Science Review, lead author Matthias Troch of Ghent University, and colleagues performed a geochemical analysis of a 12.2-meter-long sedimentary core from a region of Patagonia called the Broad Channel to determine when glaciers retreated and stabilized during geological history. Their findings on glacial ebb and flow patterns may provide insights into how glaciers in the region may respond in the future as global temperatures rise.
The Southern Patagonian Ice Field, located at the southernmost tip of South America and where the team conducted its research, is one of the two largest ice sheets in South America Patagonian Andes. ice sheet is a series of interconnected ice sheets and glaciers. Patagonia’s northern and southern ice sheets are the largest in the Southern Hemisphere outside of Antarctica. They are home to some of the world’s fastest-flowing glaciers, with ice flow rates varying between glaciers on the ice sheet.
The Southern Patagonian Ice Sheet stretches from north to south 220 milesit is drained 53 main socket glacier. The remote area is characterized by a cold and snowy climate, with high mountain peaks and cloud cover blocking most of the incoming sunlight.Westerly winds pick up huge amounts of moisture as they cross the Pacific Ocean, releasing up to 160 inches Rain falls on the mountain every year. These elements present many challenges for researchers seeking to understand the region’s shrinking glaciers; many are forced to spend weeks waiting for weather that is favorable for travel, while researchers often spend long periods of time stuck in tents waiting for unfavorable weather to turn. clear.
When ice flows over a glacier, it grinds down the rock into fine particles as it passes over the bedrock. These fine particles are carried by streams flowing off the glacier, and the sediment ends up in oceans and glacial lakes. As these sediments were deposited, they formed different layers, each from a different time period. The researchers then approached these sites with cylindrical tools to extract long cylindrical sediment samples: these samples are sediment cores. Sedimentary cores, while fascinating in their own right, contain a record of past glacier activity.
Landscapes of Chilean Patagonia (pixel fuel).
The team traveled along the ice sheet through the wide channel, taking samples from the fjord by boat. The sedimentary core consists of two main parts: gray clay at the bottom and alternating layers of dark gray, light gray and brown dirt and clay at the top.Since each layer of sediment represents a different time period and utilizes a different part of the underlying bedrock, the Magnetic Sediment particles vary in nature and size. The study authors analyzed the properties of many sediment cores to determine the grain size, rock characteristics, chronology and sediment composition of glacier patterns over the past 10-15 millennia.
The researchers analyzed a number of properties that allowed them to pinpoint the exact periods of glacial stabilization and retreat dating back to 15,000 years ago, providing valuable insights into environmental changes during those periods. The findings show that outlet glaciers fluctuated synchronously throughout many centuries of the Neoglacial Age (covering the past 5,800 years). The two major glaciers of the southern ice sheet, Penguin Glacier and Europa Glacier, remained relatively stable throughout the Holocene (11.2-5.8 millennia BP), but fluctuated greatly during the Neoglacial period. Sometimes during the Neoglacial, glaciers retreated farther inland than they do now, giving us insight into how these ice sheets might respond in the future as carbon dioxide emissions continue to rise.
Bethan Davies is a senior lecturer at the University of Newcastle, specializing in glaciology and glacial geology.in an email interview glacier center, Davis, who is not affiliated with the paper, discusses the specifics of the glacier-sediment core study. When conducting such studies, she explained, “the overall goal is twofold: to understand a process, and to understand the timing of that process.” In other words, sediment cores provide information about sediment formation, transport, and deposition processes. , the environments in which sediments occurred, and the timescales over which they occurred.
Sediment cores collected with gravity corers on the Greenland Continental Slope, Year 2008.
Understanding the details provided by sediment cores requires “specialized skills,” such as being able to recognize how the color and composition of sediments affect their surroundings, Davis said.
Sedimentary cores can reconstruct geological landscapes thousands of years ago. This is important information for addressing the current climate crisis, Davis said: “Glaciers are responding to climate change today, but the observational record is very short. To understand how they respond to extreme climate change, we need longer datasets.”
Analyzing sedimentary cores to determine periods of glacier retreat allows scientists to compare their findings with other resources, such as ice cores, to understand how the climate responds as glaciers melt and water levels rise. Most of the work on glaciers and climate takes place in the Alps, Himalayas and Alaska; recent glacier research exist PatagoniaThe large distance from other study sites may help identify similarities and differences in regional patterns.
Many Patagonian glaciers have been shrinking since the end of the century little ice age Some 150 years ago, and the accelerating rate of melting in recent years, made the Patagonian Ice Sheet one of the largest contributors to sea level rise. Therefore, understanding glacier growth and decline patterns through sediment cores is becoming increasingly important to our ability to respond to climate change.
glacier center is a climate communication initiative led by Ben Orloff, an anthropologist at the Columbia Climate Institute. Many of GlacierHub’s authors are students or alumni of the Climate School.
