Examining uncertainties regarding the relationship between heat, ice frequency, and you may sea level for the past 50 mil years
For the past ten years, operate so you’re able to estimate temperatures and sea level for the past fifty Ma have raised. Into the parallel, perform so you can model ice-sheet change during this period have been ongoing. I remark typed paleodata and you can modeling work to render insights into the just how sea level reacts so you can changing temperatures as a result of changes in frost frequency and you may thermal expansion. Up to now, heat in order to sea-level relationships might have been searched to the change out-of glacial so you can interglacial says. Tries to synthesize the temperature so you can sea level relationships within the better time, whenever heat have been rather more comfortable than just present, have been tentative. I first comment the present heat and you may sea-level research and you will model simulations, having a dialogue from uncertainty from inside the each one of these means. We up coming synthesize the sea peak and heat data and you may modeling overall performance we have reviewed to check on plausible forms into the sea level as opposed to heat relationships. With this longer timescale there are no worldwide member temperatures proxies, and therefore i investigate which dating using deep-water temperatures information and you can surface temperatures information regarding highest and you can low latitudes. It is sometimes complicated to distinguish between the additional plausible forms of the heat to help you sea-level relationship given the greater errors related on proxy estimates. We argue that to own epidermis large-latitude Southern area Hemisphere temperature and you can deep-ocean temperatures, the speed out-of changes out-of sea-level to help you temperature have not remained lingering, i.e., linear, over the past 50 Ma, whilst the matchmaking remains uncertain toward available reasonable-latitude body temperature study. Good nonlinear function between temperatures and you will sea-level was consistent with ice-sheet modeling degree. So it matchmaking can be caused by (1) the different glacial thresholds to have Southern Hemisphere glaciation versus Northern Hemisphere glaciation and you may (2) the new ice-sheet carrying strength of your Antarctic region.
step one. Inclusion
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 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 ].
For the past fifty mil age, eustatic sea-level features ranged anywhere between ?100 meters over contained in early Eocene (?56–44 Ma), whenever there is very little residential property frost on earth and you may the sea basin frequency are lower than establish [ Miller mais aussi al., 2005a ; Kominz mais aussi al., 2008 ; Miller mais aussi al., 2009a ], and you may 120–140 m lower than present [ Fairbanks, 1989 ; Yokoyama ainsi que al., 2000 ] within the last Glacial Maximum (LGM; 19–23 ka), whenever there had been higher frost sheet sets in the Antarctica, United states, China, and you may European countries [ Clark ainsi que al., 2009 ]. (Italicized conditions is outlined throughout the glossary, following the head text.) About timescale, high (greater than ten yards) eustatic sea-level distinctions was indeed brought about mainly by alterations www.datingranking.net/nl/biggercity-overzicht in the quantity out-of residential property ice [ Miller et al., 2005a ]. Broadly, there have been four ice-sheet states, these types of are (1) largely unglaciated requirements, (2) a good glaciated East Antarctic, (3) interglacial requirements with increased ice sheet sets on Western Antarctic and you will Greenland (i.elizabeth., present-time conditions), and you may (4) glacial requirements on the a lot more development of large freeze sheets into the the fresh new Northern Hemisphere [ de Boer mais aussi al., 2012 ]. The latest glaciation of your own Eastern Antarctic is also after that busted on to an advanced county with ephemeral slope freeze caps and you will a fully glaciated state [ ].