abrupt là gì

The last glacial period is characterized by a number of millennial climate events that have been identified in both Greenland and Antarctic ice cores and that are abrupt in Greenland climate records. The mechanisms governing this climate variability remain a puzzle that requires a precise synchronization of ice cores from the two hemispheres to tát be resolved. Previously, Greenland and Antarctic ice cores have been synchronized primarily via their common records of gas concentrations or isotopes from the trapped air and via cosmogenic isotopes measured on the ice. In this work, we apply ice core volcanic proxies and annual layer counting to tát identify large volcanic eruptions that have left a signature in both Greenland and Antarctica.

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Generally, no tephra is associated with those eruptions in the ice cores, sánh the source of the eruptions cannot be identified. Instead, we identify and match sequences of volcanic eruptions with bipolar distribution of sulfate, i.e. unique patterns of volcanic events separated by the same number of years at the two poles. Using this approach, we pinpoint 82 large bipolar volcanic eruptions throughout the second half of the last glacial period (12–60 ka). This improved ice core synchronization is applied to tát determine the bipolar phasing of abrupt climate change events at decadal-scale precision. In response to tát Greenland abrupt climatic transitions, we find a response in the Antarctic water isotope signals (18O and deuterium excess) that is both more immediate and more abrupt than thở that found with previous gas-based interpolar synchronizations, providing additional tư vấn for our volcanic framework.

On average, the Antarctic bipolar seesaw climate response lags the midpoint of Greenland abrupt δ18O transitions by 122 +/- 24 years. The time difference between Antarctic signals in deuterium excess and δ18O, which likewise informs the time needed to tát propagate the signal as described by the theory of the bipolar seesaw but is less sensitive to tát synchronization errors, suggests an Antarctic δ18O lag behind Greenland of 152 +/- 37 years. These estimates are shorter than thở the 200 years suggested by earlier gas-based synchronizations.

As before, we find variations in the timing and duration between the response at different sites and for different events suggesting an interaction of oceanic and atmospheric teleconnection patterns as well as internal climate variability.

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Figure:  (a) Stack of Greenland NGRIP isotopes and CH4 for the onsets of GI events. (b) Antarctic five-core mean δ18O (stack of 5*21 warming events); grey curve applies the bipolar methane synchronization of WAIS Divide Project Members (2015); (c) Antarctic five-core mean deuterium excess (dln)

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