The West without Water: What Past Floods, Droughts, and Other Climatic Clues Tell Us about Tomorrow
- The history of the earth
Archaeologists excavate clues that were left behind by prehistoric societies. These clues include things like chipped stones, beads, bones, bits of broken pottery, and so on. They do so through sifting or filtering through olden garbage as well as other remains that can give clues about their daily lives. As a result of systematically sifting through as well as scrutinizing the preserved prehistoric remains, it becomes possible for archaeologist to deduce more about the ancient civilization, rises and falls, and their daily lives. Likewise, paleoclimatologists always desire to learn about the climatic history of the earth, including patterns of warm and cold, wet and dry seasons, so on. To do so, they search for clues that are buried in trees, corals, fossils, glaciers, and sediments preserved in oceans, marshes, and lakes (Fagan 2).
- The Holocene period
In the modern time, people are living in a relatively cool periods that are perceived to have commenced about forty million years ago. Throughout this period, the earth continued to become more and more cool and icy, ending in the Quaternary Period (Pleistocene and Holocene period), a dance of decades ago. Historical research indicates that the most recent glacial period managed to reach its maximum extent after a duration of about 20 thousand years that have passed, a period termed as the Last Glacial Maximum (Fagan 17). During this period, the average world temperature was about 1.8o F which is relatively lower as compared to the modern global temperatures.
Currently, the world is in a relatively warmer interglacial period that is dubbed as the Holocene epoch which started about 11 thousand years ago. The ancient lakebeds in the American West enable paleoclimatologists clues concerning the prehistoric climate, including the overall decrease in precipitation, and in trajectories, spatial variations, and rates, in change at the start and the end. On the other hand, during the Mid Holocene period, the climatic conditions of the American West shifted from cooler to warmer and drier conditions (Fagan 18). To the big lakes like the Owens Lake, the changes which occurred within Owens Valley had a profound impact to the disappearance of these lakes. As a result of climatic changes (dry conditions), these rivers started to receive little precipitations hence making its water volume to fluctuate. As time went by, they all dried up leaving flat sediments composed of evaporated minerals, silt, and clay (Fagan 31).
The climatic upheaval accompanied with extended drought forced people to depart their ancestral terrain in search of food and water, particularly in the Great Britain now termed as southeastern California. Inland areas were the ones that was highly affected, and as a result of that, evidences obtained by archaeologists suggests that thousands of people were forced to migrate to the coast. The reason for that is because it offered plentiful food, more moisture, and cooler climate (Fagan 20). Along the coastline, the steady rise in sea level succeeding the previous ice age started to slow down after the massive inflow of waters from melting ice.
- The neoglaciation: The returning of ice
During the mid-Holocene period, the warm and dry conditions gradually paved way to cool and wet conditions dubbed as the Neoglaciation. Although it did not have a clear demarcate beginning, it settled unevenly throughout the Northern Hemisphere with some considerable local variations. In Europe, especially in the Swiss and Australian Alps and southern Norway, the beginning of this cooler climatic condition had started over 4-5 thousand years ago, taking into account the dating of the sediments and glacial moraines that were eroded by glaciers as well as transported by water melting from glaciers (Fagan 44).
The sediments, silts and clays that were transported into San Francisco Bay from its watershed, carry carried with them chemical and mineral fingerprints of the area of origin. In the process of carrying them to S.F Bay, the majority of largest particles had settled to the underneath the estuary while lighter and finer particles were transported to the surrounding marshes which in return formed progressively accumulating layers. On the other hand, the northern regions of the watershed were drained by the Sacramento River thus transporting sediments (silts and clays) from the northern parts of the Sierra Nevada and the southern Cascades. The sediments of the southern parts of the watershed were also drained by the San Joaquin River (Fagan 48).
Therefore, to paleoclimatologists, the general composition of these sediments acts as valuable fingerprints for detecting the area of their origin. Moreover, from the northern to the southern regions of the watershed, the changing proportions of these sediments aid in providing detailed information concerning how the climatic conditions of the northern and southern California could have changed for decades. It, therefore, implies that these changes assist in showing that the medieval droughts were ultimately experienced all over the watershed of the S.F estuary although not at the same period.
- The Great Medieval Drought
The cooler and the moist climatic conditions of the Neoglacial era came to an end during the late Holocene. The climate had started changing to drier and warmer conditions about 185o years that had passed and persisted for a period of at least thousand years. Despite that the fact that the trend of the climatic conditions of the contemporary western U.S was heading to dryness, conditions continued to become more and more variable. For instance, prolonged drought conditions were later intermingled with gradual excursions of intense wetness. The paleoclimatic statistics that was captured for about 1800 years that have passed contain several examples and indicators of such climatic variations (Fagan 53).
During The Little Ice Age, the prolonged droughts of the medieval climate anomaly finally came closer at around 1400 AD. For duration of about 150 years after this period, an extreme flood was something that was unusual. In California, for instance, people who were residing around San Francisco Bay and in the wider Central Valley could have witnessed irregular rainfall patterns for decades. During this time, winters could have failed to produce huge storms that fed the mountain snowpack and fill lakes. Around the San Francisco Bay, mounded villages remained empty for several years since the start of the drought. Moreover, early in summer, the creeks that used to flow into the marshlands also dried up thus leaving people with no choice but to travel for long distances in search of freshwater. For those whose camps were located inland, they were forced to do long journey to mudflats to collect muscles as well as other shellfish. The majority of the native population greatly suffered to death although some managed to adapt to the prevailing dry conditions (Fagan 72).
Later, the weather started changing and for those who managed to adapt with it noticed wet season accompanied by cold storms which later poured rain in the coastal region, in the lower mountainous regions, and in the Central Valley. Winters, also started bringing cooler storms than it used to be. Elsewhere around the world, especially in Europe, canals and rivers started freezing and in Alaska, New Zealand, central and northern Europe valley glaciers grew larger in thickness. Summer temperatures also decreased considerably in Europe hence resulting to crop failures in Switzerland, Norway, and Scotland which in return caused widespread famine. In California, the storms that had originated from the tropical regions of the Pacific ended op delivering plentiful warm rainfall that caused huge flooding within the region. The rapidly melting snow and the rain increased the swelling of rivers and small creeks into ranging torrents, tearing soils and vegetation found in the mountain regions, as well as turning the Central Valley of California into immense inland sea (Fagan 73).
Therefore, we can depict that there are two lessons learned from the Little Ice Age. The first one is that climate change does not necessarily come in an easy or gentle stage. It always comes in rapid shifts from one period to another. This shifts are something that is beyond human understanding because its directions are also far beyond human control. Secondly, climate will always have its way of changing regimes and its sway in human occurrences. This then implies that the Little Ice Age is typically a record of human susceptibility to climatic changes.
- Cycles and oscillations resulting to climatic changes
For million years that have passed, forces lying within the earth are the ones perceived to be causing climate change. In the process of moving tectonic plates, the same process ends up building mountains and spreading water bodies apart (Fagan 84). For instance, in shallow tropical seas, for millions of years, tiny polyps have managed to build brilliant coral reefs. Such an ecosystem is amongst the richest and magnificent communities of species that have survived for millions of years that have passed. Moreover, the recent coral reefs that have been probed by paleoclimatic scientists offers evidence regarding the ancient behaviors of the ocean-atmosphere phenomenon termed as the ENSO (El Nino-Southern Oscillation). The failing of the trade wings during this event causes the western Pacific Ocean waters to drift eastwards, warming water which in return warms shallow coral reefs (Fagan 86).
Furthermore, the information regarding the strength of the PDO (Pacific Decadal Oscillation) suggest that whenever it is in a cool or negative phase, the ocean surface temperatures are relatively cooler and when it is in a warm or positive phase, it means that the ocean water is typically warmer than average. The cool or negative phase indicates the sea conditions during the Holocene period when the waters of the Pacific coast used to be cooler. During this period, conditions were in the Pacific Northwest were wetter as well as drier in the interior western and southwest North America. Conversely, the Neoglacial wet conditions that later followed is found to have corresponded with PDO when in the warm (positive) phase (Fagan 87).
In the late Holocene era, the cool (negative) phase of the PDO was marked by prolonged extreme droughts. The connections that existed between the two can be deduced from the tree-ring information. Such information suggests that Northwest was wet while Southwest was dry at that time. Another important factor is the sunspot cycles.
