Sea surface temperature (SST) proxies suggest that during the Eocene, the high latitudes were significantly warmer than present, approaching or even exceeding temperatures seen in the modern tropics [ Bijl et al., 2009 ; Hollis et al., 2009 ; Liu et al., 2009 ; Bijl et al., 2010 ]. , 2006 ; Lear et al., 2008 ; Keating-Bitonti et al., 2011 ], suggesting that there was a much reduced latitudinal temperature gradient [ Huber, 2008 ; Bijl et al., 2009 ]. During glacial conditions, the surface high latitudes show cooling [ Jouzel et al., 2007 ], with this cooling also extending to low latitudes, suggesting that there were additional feedbacks on the climate system, such as CO2 feedbacks, in addition to orbital driven forcing [ Herbert et al., 2010 ; Rohling et al., 2012 ].
For the past fifty Ma around have also been significant tectonic transform, for instance the uplift of one’s Himalayas adopting the collision out of India that have China, the hole of the https://datingranking.net/nl/feeld-overzicht Drake and you can Tasman verses, together with closing of Panama seaway, having most of the got an impact on the climate system [ Zachos ainsi que al., 2001 ].
1.step one. Temperatures so you’re able to Sea level Matchmaking
Surface temperature is about sea level and their handle on the amount of freeze kept on residential property and you can through thermal expansion. Sea-level reaction to temperature forcing for the past 0.5 Ma could have been read having fun with proxy study out-of freeze cores, water sediments, and you may fossil corals [ Rohling mais aussi al., 2009 ; Siddall mais aussi al., 2010a , 2010b ]. Although not, for longer symptoms (10 6 –ten eight years), just modeled prices have been authored, albeit restricted by the data [ de- Boer mais aussi al., 2010 ]. Here we use current proxy suggestions in the early in the day fifty Ma to analyze the connection and you will uncertainties anywhere between temperatures and you can sea level into the change so you can an enthusiastic “ice-house” community. There aren’t any in the world user heat proxies on this timescale; rather, i check out the the relationship using DST and you may skin temperatures from large and lower latitudes.
When examining which few years months, new proxy number out-of facial skin temperature is restricted in cycle and you will spatial visibility, regardless if records try boosting to the continued development of the brand new and you will established proxies [ Lear ainsi que al., 2008 ; Liu et al., 2009 ]. A limitation of employing isolated facial skin heat proxies would be the fact around is actually built-in concerns about whether local and you can/or regular temperatures movement are being registered [ Lear ainsi que al., 2000 ]. Such potential biases try reduced in this new DST number, as the DST number enjoys other extreme limitations [ Lear mais aussi al., 2000 ; Billups and you can Schrag, 2003 ]. DST is actually paired in order to SST from the areas of strong-h2o development, and therefore toward modern day was mostly, yet not exclusively [ Gebbie and you may Huybers, 2011 ], the brand new highest latitudes [ Zachos et al., 2001 ]. Therefore, DST proxies should not be thought to be a record of earlier international temperature but should as an alternative be considered as the analogous so you can earlier high-latitude skin heat [ Zachos et al., 2001 ]. New DST checklist excellent whenever exploring the ocean peak in order to heat matchmaking, as it’s top combined toward surface on aspects of frost creation.
step one.dos. Opinion Description
Most which opinion is mostly about the latest DST in order to sea-level relationships over the past 50 Ma, once the DST record is much more done compared to epidermis heat listing. Likewise, i investigate the exterior temperature to sea level matchmaking over a great trick interval for sea-level alter, this new Eocene-Oligocene changeover (EOT). The newest lead interpretation amongst the DST so you’re able to sea-level relationship to the outside temperature to help you sea-level matchmaking lies in this new existence out of a steady deep-ocean in order to epidermis heat gradient thanks to go out. We is a discussion regarding the deep-ocean in order to epidermis temperatures gradient may have changed along side multimillion season timescale with the studies on account of changes in water movement and you will modifying types of strong-h2o formation [ Cramer et al., 2009 ; Katz et al., 2011 ].