However, a particular constraint on these studies is the limited amount of high-quality measurements in the abyssal region, in waters deeper than ~2000 m (e.g., Wunsch, 2016 Johnson et al. Measuring programs, like Argo, together with historical and quality controlled hydrographic data are the prime sources of empirical information for ocean climate change studies. A global average estimate shows warming, over the last decade, of 50 m☌ decade −1 for waters between the surface and 500 m and of 20 m☌ decade −1 from 500 to 2000 m ( Roemmich et al. The outstanding Argo program provides measurements from the top 2000 m of the global ocean since 2006 ( Roemmich et al. The large amount of studies aiming at measuring and understanding climate change shows the importance of having long and accurate temperature records. A simple box model connects the observed warming, well within the Gulf interior, with that expected in the densest waters that spill from the North Atlantic into the Cayman Basin through Windward Passage and suggests that the source waters at the entrance to the Caribbean have been warming for at least 100 years. The densest waters that spill into the Gulf of Mexico, over the Yucatan Channel sill, must mix substantially during their descent and in the near-bottom interior, losing their extreme values. The bottom geothermal heat flux is a contributing factor to be considered in the warming and renewal of such waters, but it has not changed over millennia and is therefore unlikely to be the cause of the observed trend. Within the western Gulf of Mexico, near-bottom measurements at ~3500-m depths at four sites show a stable linear warming trend of ~16 ± 2 m☌ decade −1 for the period 2007–18, and CTD data from eight oceanographic cruises occurring from 2003 to 2019 show a trend of ~18 ± ~2 m☌ decade −1 from the bottom to ~2000 m below the surface. Semi-enclosed basins, such as the Gulf of Mexico, are of particular interest as the waters below sills that connect with the neighboring oceans have residence times much longer than upper layers. Since surface and near-surface oceanic temperatures have been measured far more frequently in time and space than deep waters (>2000 m), deep measurements become quite valuable. A key consequence in climate change is the warming of deep waters, away from the faster warming rates of near-surface subtropical and tropical waters.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |