Examining uncertainties regarding relationship ranging from temperatures, ice regularity, and you can sea level over the past fifty mil years
Investigating uncertainties on the relationship ranging from temperatures, freeze regularity, and you may sea level for the past fifty billion ages
For the past a decade, services so you can imagine heat and you will sea level over the past fifty Ma have increased. Into the synchronous, efforts so you’re able to model ice sheet transform during this time was basically ongoing. I comment published paleodata and you will acting try to bring insights for the just how sea level responds so you’re able to switching heat as a result of alterations in frost regularity and you will thermal expansion. Thus far, the warmth so you’re able to sea-level relationships has been explored with the changeover regarding glacial so you’re able to interglacial claims. Tries to synthesize the temperature to sea level matchmaking within the deeper time, when heat had been significantly warmer than just expose, was indeed tentative. We very first opinion current temperatures and you may sea level analysis and you will model simulations, that have a dialogue out of suspicion inside the each one of these steps. We then synthesize the ocean top and temperature research and you may acting overall performance i’ve reviewed to evaluate possible variations to the sea top versus temperatures matchmaking. About this longer timescale there aren’t any internationally user temperatures proxies, and thus we have a look at this relationships having fun with deep-sea temperatures suggestions and you will skin temperature details from highest and you can reasonable latitudes. It is hard to identify involving the various other possible kinds of the warmth to help you sea level relationships because of the greater mistakes relevant towards the proxy estimates. We believe getting body highest-latitude South Hemisphere heat and you will strong-ocean temperatures, the pace away from change off sea level to help you temperatures have not remained constant, we.age., linear, for the past fifty Ma, although the relationship remains ambiguous on offered lower-latitude skin heat study. A nonlinear mode between temperature and you may sea-level is actually in keeping with ice-sheet modeling education. That it dating should be related to (1) the different glacial thresholds having South Hemisphere glaciation compared to the Northern Hemisphere glaciation and you will (2) the new ice-sheet carrying strength of Antarctic continent.
step one. Introduction
Understanding and predicting glacier and ice sheet dynamics is notoriously difficult [ Alley et al., 2005 ; Allison et al., 2009 ], and as a result, in their fourth assessment report the Intergovernmental Panel on Climate Change did not provide sea level projections that accounted for rapid dynamical changes in ice flow [ Solomon et al., 2007 ]. The observational record contains worrying examples of nonlinear threshold type responses, such as the collapse of the Larsen B ice shelf is clover dating gratis and subsequent surging of glaciers [ De Angelis and Skvarca, 2003 ; Rignot et al., 2004 ]. However, the observational record does not help us constrain large changes to the ice sheets. Although there is no known analog to projected future warming in the paleoclimate record [ Crowley, 1990 ; Haywood et al., 2011 ], it does contain examples of large-scale changes to the ice sheets [ a ]. The paleoclimate record can therefore aid understanding of ice sheet behavior and provide insight into the plausibility of large ice sheet changes in a warming world [ Scherer et al., 1998 ; Pollard and ]. By looking to the paleoclimate record we can also attempt to better understand the relationship between different climate parameters, such as temperature, atmospheric CO2, ice volume, and sea level [ Rohling et al., 2009 ].
Over the past fifty billion ages, eustatic sea-level features ranged ranging from ?100 meters above within early Eocene (?56–forty-two Ma), when there’s little or no property freeze on the planet and you may the ocean basin frequency try lower than introduce [ Miller mais aussi al., 2005a ; Kominz et al., 2008 ; Miller et al., 2009a ], and you can 120–140 yards less than establish [ Fairbanks, 1989 ; Yokoyama ainsi que al., 2000 ] in the last Glacial Limit (LGM; 19–23 ka), when there are large ice sheet sets within the Antarctica, North america, China, and European countries [ Clark mais aussi al., 2009 ]. (Italicized terms are defined on the glossary, adopting the head text message.) About this timescale, highest (higher than ten meters) eustatic sea-level distinctions was indeed brought about predominately because of the changes in the volume out of homes ice [ Miller ainsi que al., 2005a ]. Broadly, there are four ice sheet states, these being (1) mainly unglaciated standards, (2) a glaciated East Antarctic, (3) interglacial standards with frost sheets on the Western Antarctic and you will Greenland (i.e., present-go out criteria), and (4) glacial conditions to the a lot more development of highest ice sheets during the the fresh new North Hemisphere [ de Boer ainsi que al., 2012 ]. The newest glaciation of the Eastern Antarctic can be subsequent damaged down into an advanced state with ephemeral slope ice hats and you will a fully glaciated condition [ ].